Builders Foundation Handbook

OAK RIDGENATIONALLABORATORY

MANAGED BYMARTIN MARIETTA ENERGY SYSTEMS, INC. FOR THE UNITED STATESDEPARTMENT OF ENERGY

ORNL/CON-295

John CarmodyJeffrey Christian

Kenneth Labs

Part of the National Program forBuilding Thermal Envelope Systems and Materials

Prepared for theU.S. Departmet of Energy

Conservation and Renewable EnergyOffice of Buildings and Community Systems

Building Systems Division

Builder’s FoundationHandbook

This report has been reproduced directly from the best available copy.

Available to DOE and DOE contractors from the Office of Scientific andTechnical Information, P.O. Box 62, Oak Ridge, TN 37831; prices availablefrom (615) 576-8401, FTS 626-8401.

Available to the public from the National Technical Information Service,U.S. Department of Commerce, 5285 Port Royal Rd., Springfield, VA 22161.

This report was prepared as an account of work sponsored by an agency ofthe United States Government. Neither the United States Government nor anyagency thereof, nor any of their employees, makes any warranty, express orimplied, or assumes any legal liability or responsibility for the accuracy,completeness, or usefulness of any information, apparatus, product, orprocess disclosed, or represents that its use would not infringe privatelyowned rights. Reference herein to any specific commercial product, process,or service by trade name, trademark, manufacturer, or otherwise, does notnecessarily constitute or imply its endorsement, recommendation, or favoringby the United States Government or any agency thereof. The views andopinions of authors expressed herein do not necessarily state or reflect thoseof the United States Government or any agency thereof.

John CarmodyUnderground Space Center

University of Minnesota

Jeffrey ChristianOak Ridge National Laboratory

Oak Ridge, Tennessee

Kenneth LabsUndercurrent Design Research

New Haven, Connecticutt

Book Design and Illustrations: John Carmody

Date of Publication: May, 1991

Prepared for:

Oak Ridge National LaboratoryOak Ridge, Tennessee 37831

Operated by:

Martin Marietta Energy Systems, Inc.for the U. S. Department of Energy

under Contract DE-AC05-84OR21400

Builder’s FoundationHandbook

Builder’s Foundation Handbook Page v

List of Figures and Tables

Chapter 1 Figures

Figure 1-1: The impact of basement insulation is monitored on several modules at thefoundation test facility at the University of Minnesota.

Figure 1-2: Benefits of Foundation Insulation and Other Design ImprovementsFigure 1-3: The impact of slab-on-grade foundation insulation is monitored in a test

facility at Oak Ridge National Laboratory.Figure 1-4: Decision-Making Process for Foundation DesignFigure 1-5: Basic Foundation TypesFigure 1-6: Points of Radon Entry into Buildings

Chapter 2 Figures

Figure 2-1: Concrete Masonry Basement Wall with Exterior InsulationFigure 2-2: Components of Basement Structural SystemFigure 2-3: Components of Basement Drainage and Waterproofing SystemsFigure 2-4: Termite Control Techniques for BasementsFigure 2-5: Radon Control Techniques for BasementsFigure 2-6: Soil Gas Collection and Discharge TechniquesFigure 2-7: System of Key Numbers in Construction Drawings that Refer to Notes on

Following PagesFigure 2-8: Concrete Basement Wall with Exterior InsulationFigure 2-9: Concrete Basement Wall with Exterior InsulationFigure 2-10: Masonry Basement Wall with Exterior InsulationFigure 2-11: Concrete Basement Wall with Interior InsulationFigure 2-12: Concrete Basement Wall with Ceiling InsulationFigure 2-13: Pressure-Preservative-Treated Wood Basement Wall

Chapter 3 Figures

Figure 3-1: Concrete Crawl Space Wall with Exterior InsulationFigure 3-2: Components of Crawl Space Structural SystemFigure 3-3: Crawl Space Drainage TechniquesFigure 3-4: Crawl Space Drainage TechniquesFigure 3-5: Termite Control Techniques for Crawl SpacesFigure 3-6: Radon Control Techniques for Crawl SpacesFigure 3-7: System of Key Numbers in Construction Drawings that Refer to Notes on

Following PagesFigure 3-8: Vented Crawl Space Wall with Ceiling InsulationFigure 3-9: Unvented Crawl Space Wall with Exterior InsulationFigure 3-10: Unvented Crawl Space Wall with Interior InsulationFigure 3-11: Unvented Crawl Space Wall with Interior Insulation

Page vi

Chapter 4 Figures

Figure 4-1: Slab-on-Grade Foundation with Exterior InsulationFigure 4-2: Structural Components of Slab-on-Grade Foundation with Grade BeamFigure 4-3: Structural Components of Slab-on-Grade Foundation with Stem Wall and

FootingFigure 4-4: Drainage Techniques for Slab-on-Grade FoundationsFigure 4-5: Termite Control Techniques for Slab-on-Grade FoundationsFigure 4-6: Radon Control Techniques for Slab-on-Grade FoundationsFigure 4-7: Soil Gas Collection and Discharge TechniquesFigure 4-8: System of Key Numbers in Construction Drawings that Refer to Notes on

Following PagesFigure 4-9: Slab-on-Grade with Integral Grade Beam (Exterior Insulation)Figure 4-10: Slab-on-Grade with Brick Veneer (Exterior Insulation)Figure 4-10: Slab-on-Grade with Brick Veneer (Exterior InsulationFigure 4-12: Slab-on-Grade with Masonry Wall (Exterior Insulation))Figure 4-13: Slab-on-Grade with Concrete Wall (Insulation Under Slab)Figure 4-14: Slab-on-Grade with Masonry Wall (Insulation Under Slab)Figure 4-15: Slab-on-Grade with Masonry Wall (Interior Insulation)Figure 4-16: Slab-on-Grade with Brick Veneer (Insulation Under Slab)

Chapter 5 Figures

Figure 5-1: Steps in Worksheet to Determine Optimal Foundation InsulationFigure 5-2: Formulas Used as a Basis for Worksheet 1Figure 5-3: Formulas Used as a Basis for Worksheet 3

Chapter 2 Tables

Table 2-1: Insulation Recommendations for Fully Conditioned Deep BasementsTable 2-2: Insulation Recommendations for Unconditioned Deep BasementsTable 2-3: Fuel Price Levels Used to Develop Recommended Insulation Levels in Tables 2-

1 and 2-2

Chapter 3 Tables

Table 3-1: Insulation Recommendations for Crawl SpacesTable 3-2: Fuel Price Levels Used to Develop Recommended Insulation Levels in Table 3-1

Chapter 4 Tables

Table 4-1: Insulation Recommendations for Slab-on-Grade FoundationsTable 4-2: Fuel Price Levels Used to Develop Recommended Insulation Levels in Table 4-1

Chapter 5 Tables

Table 5-1: Weather Data for Selected Cities (page 1 of 2)Table 5-2: Insulation R-Values and Costs for Conditioned Basements (page 1 of 4)Table 5-2: Insulation R-Values and Costs for Slab-on-Grade Foundations (page 4 of 4)Table 5-3: Heating Load Factor Coefficients (HLF

I and HLF

S)

Table 5-4: Cooling Load Factor Coefficients (CLFI and CLF

S)

Table 5-5: Initial Effective R-values for Uninsulated Foundation System and Adjacent SoilTable 5-6: Heating and Cooling Equipment Seasonal Efficiencies1

Table 5-7: Scalar Ratios for Various Economic CriteriaTable 5-8: Energy Cost Savings and Simple Paybacks for Conditioned BasementsTable 5-8: Energy Cost Savings and Simple Paybacks for Conditioned BasementsTable 5-10: Energy Cost Savings and Simple Paybacks for Crawl Space FoundationsTable 5-11: Energy Cost Savings and Simple Paybacks for Slab-on-Grade Foundations

Builder’s Foundation Handbook Page vii

PrefaceThis handbook is a product of the U.S.

Department of Energy Building EnvelopeSystems and Materials (BTESM) ResearchProgram centered at the Oak Ridge NationalLaboratory. The major objective of thisresearch is to work with builders, contractors,and building owners to facilitate the reality ofcost-effective energy efficient walls, roofs,and foundations on every building. Thishandbook is one of a dozen tools producedfrom the BTESM Program aimed at relevantdesign information in a usable form duringthe decision-making process.

The Builder’s Foundation Handbookcontains a worksheet (Chapter 5) to helpselect insulation levels based on specificbuilding construction, climate, HVACequipment, insulation cost, and othereconomic considerations. This worksheetpermits you to select the optimal insulationlevel for new and retrofit applications.

This handbook contains constructiondetails representative of good practices forthe design and installation of energy efficientbasement, crawl space, and slab-on-gradefoundations. In the preface to the BuildingFoundation Design Handbook published in1988, I asked for comments on how toimprove future editions. Most of thesuggestions received have been incorporatedinto this version. For example, onesuggestion was to add a detail showing howto insulate a slab-on-grade foundationsupporting an above-grade wall with brickveneer. This detail appears as Figure 4-10.

The construction details are accompaniedby critical design information useful forspecifying structural integrity; thermal andvapor controls; subsurface drainage;waterproofing; and mold, mildew, odor,decay, termite, and radon control strategies.Another useful feature is a checklist whichsummarizes the major design considerationsfor each foundation type—basement(Chapter 2), crawl space (Chapter 3), and slab

(Chapter 4). These checklists have beenfound to be very useful during the designstage and could be very useful duringconstruction inspection.

The first foundation handbook from theBTESM program—the Building FoundationDesign Handbook—was released to the publicin May 1988. Since that time severalsignificant national codes have adoptedfoundation insulation levels based onresearch results from this program. InOctober 1988, the Council of AmericanBuilding Officials Model Energy CodeCommittee accepted an upgrade to moreenergy efficient foundations. Several stateshave adopted the Model Energy Code intotheir building inspection programs includingIowa and Utah. The Department of Housingand Urban Development (HUD) MinimumProperty Standard also looks as if it is goingto adopt these foundation insulationrecommendations.

Foundation insulation is gainingacceptance in the U.S. residential buildingindustry. Moisture and indoor air qualityproblems caused by faulty foundation designand construction continue to grow inimportance. The material contained in thishandbook represents suggestions from adiverse group of knowledgeable foundationexperts and will help guide the builder tofoundation systems that are easilyconstructed and that have worked for othersin the past, and will work for you in thefuture.

I welcome your response to thishandbook. Please send me your commentsand suggestions for improving futureeditions.

Jeffrey E. ChristianOak Ridge National LaboratoryP.O. Box 2008Building 3147 MS 6070Oak Ridge, TN 37831-6070

Page viii

Builder’s Foundation Handbook Page ixPage ix

AcknowledgmentsThis handbook, directed at builders,

grew from a “brain storming” sessionincluding representatives from the researchand building communities back in 1987. Itwas recognized that after development of amore comprehensive design manual, theBuilding Foundation Design Handbook (Labs, etal. 1988), it would be desirable to condensethe pertinent information into a handbook forbuilders.

The authors are grateful to all those whoparticipated in the development of the earlierBuilding Foundation Design Handbook, fromwhich most of the material in this handbookis drawn. In particular we acknowledge thecontributions of the following authors of theoriginal book: Raymond Sterling, LesterShen, Yu Joe Huang, and Danny Parker.

Funding support for this report camefrom Sam Taylor and John Goldsmith at theU.S. Department of Energy. Sam Taylor alsoinsisted on a high quality book with aninviting format to better convey theimportant messages contained in all this fineprint.

The handbook was graciously reviewedand enhanced by a number of foundationexperts. Several of the reviewers provided

lengthy lists of constructive suggestions: DonLeubs, National Association of HomeBuilders/National Research Center; MarkKelly, Building Science Engineering; PhilHendrickson, Dow Chemical; Peter Billings,National Forest Products Association; J.D.Ned Nisson, Energy Design Update; MarkFeirer, Fine Homebuilding; Steven Bliss,Journal of Light Construction; Bob Wendt,Oak Ridge National Laboratory; Ron Graves,Oak Ridge National Laboratory; Martha VanGeem, Construction TechnologyLaboratories; Dave Murane, EnvironmentalProtection Agency; Roy Davis and Pat Rynd,UC Industries, Inc.; Jon Mullarky and JimRoseberg, National Ready Mix ContractorAssociation; Donald Fairman and WilliamFreeborne, U.S. Department of Housing;Douglas Bowers, Geotech; Joe Lstiburek; JohnDaugherty, Owens-Corning Fiberglas; andTom Greeley, BASF Corporation.

All of the drawings and the graphicdesign of the handbook were done by JohnCarmody of the Underground Space Centerat the University of Minnesota. The authorsappreciate the contribution of Pam Snoplwho edited the final manuscript.

Page x

Builder’s Foundation Handbook Page xi

AbstractThis handbook contains a worksheet for

selecting insulation levels based on specificbuilding construction, climate, HVACequipment, insulation cost, and othereconomic considerations. The worksheetpermits optimization of foundationinsulation levels for new or retrofitapplications. Construction detailsrepresenting good practices for the designand installation of energy efficient basement,crawl space, and slab-on-grade foundationsare the focal point of the handbook. Theconstruction details are keyed to lists ofcritical design information useful forspecifying structural integrity; thermal andvapor control; subsurface drainage;waterproofing; and mold, mildew, odor,decay, termite, and radon control strategies.Another useful feature are checklist chaptersummaries covering major design

considerations for each foundation type--basement, crawl space, and slab-on-grade.These checklist summaries are useful duringdesign and construction inspection. Theinformation in this handbook is drawnheavily from the first foundation handbookfrom the DOE/ORNL Building EnvelopeSystems and

Materials Program, the BuildingFoundation Design Handbook (Labs et al., 1988),which is an extensive technical referencemanual. This book presents “what to do infoundation design” in an inviting, conciseformat. This handbook is intended to servethe needs of active home builders; however,the information is pertinent to anyoneinvolved in foundation design andconstruction decisions includinghomeowners, architects, and engineers.

Builder’s Foundation Handbook Page 1

The foundation of a house is a somewhatinvisible and sometimes ignored componentof the building. It is increasingly evident,however, that attention to good foundationdesign and construction has significantbenefits to the homeowner and the builder,and can avoid some serious future problems.Good foundation design and constructionpractice means not only insulating to saveenergy, but also providing effectivestructural design as well as moisture, termite,

and radon control techniques whereappropriate.

The purpose of this handbook is toprovide information that will enabledesigners, builders, and homeowners tounderstand foundation design problems andsolutions. This chapter provides the generalbackground and introduction to foundationdesign issues. Section 1.1 explains thepractical and economic advantages of goodfoundation design. The organization and

Figure 1-1: The impact of basement insulation is monitored on several modules at the foundation testfacility at the University of Minnesota.

CHAPTER 1

Introduction toFoundation Design

Chapter 1—Introduction to Foundation Design

is one major concern that is relatively new—controlling radon. Because radon representsa potentially major health hazard, andknowledge about techniques to control it arejust emerging, a special introduction to radonappears in section 1.4. This chapter isintended to set the stage for the moredetailed information found in chapters 2through 5.

1.1 Benefits of EffectiveFoundation Design

The practical and economic advantagesof following the recommended practices inthis handbook are:

• Homeowners' utility bills are reduced.

• Potentially costly future moisture, termite,and even structural problems can beavoided.

• Potentially serious health-related effects ofsoil gas can be avoided.

• More comfortable above-grade space iscreated.

• For houses with basements, trulycomfortable conditions in below-gradespace are created.

All these potential advantages are sellingpoints and can help builders avoid costlycallbacks.

The Benefits of Foundation Insulation

The primary reason behind the currentinterest in foundation design andconstruction is related to energyconservation, although in some areas radoncontrol is also a primary concern. Today'sprospective home buyers are increasinglydemanding healthy, energy-efficient homesthat will provide the most comfort for theirfamilies at a reasonable price. In the past, theinitial cost and the monthly mortgagepayment were the critical criteria considered.Now, with rising energy costs, operatingexpenses are also a prime consideration andexert a major influence upon the moreeducated home buyer’s decision. Homebuyers want a home they can not only affordto buy—they want one they can also afford tolive in.

Home builders and code officials have

scope of this handbook is described in section1.2. Before proceeding with solving designand problems, there must be a basic decisionabout the type of foundation to be used—basement, crawl space, or slab-on-grade.Section 1.3 discusses the considerations thataffect choosing a foundation type. Whilemany aspects of foundation design andconstruction are known to some extent, there

Figure 1-2: Benefits of Foundation Insulationand Other Design Improvements

REDUCTION IN HOMEOWNER'SUTILITY BILLS

CREATION OF MORECOMFORTABLE

ABOVE-GRADE SPACES

AVOIDANCE OF COSTLY MOISTURE, TERMITE, ANDSTRUCTURAL PROBLEMS

CREATION OF MOREUSABLE, COMFORTABLEBELOW-GRADE SPACES

AVOIDANCE OF HEALTH-RELATED

EFFECTS OF SOIL GAS


initially responded to these desires byproviding more thermal insulation in theabove-grade portions of the home. Attentionto the foundation has lagged for the mostpart, with most effort focused primarily on afoundation's structural adequacy. Latelyhowever, the general awareness of health-oriented, energy-efficient foundationconstruction practices has increased in theUnited States. In 1989-90 several nationalbuilding energy codes and standards wererevised to recommend foundation insulationin moderate to cold U.S. climates (those withover 2500 heating degree days). Uninsulatedfoundations no longer represent 10 to15 percent of a poorly insulated building’stotal heat loss; instead, an uninsulated,conditioned basement may represent up to 50percent of the heat loss in a tightly sealedhouse that is well insulated above grade.

In order to develop a betterunderstanding of the impact of foundationinsulation and provide information to thebuilding industry and the public, severalresearch activities are proceeding. Twonotable projects are the foundation test

facilities located at the University ofMinnesota (Figure 1-1), and at Oak RidgeNational Laboratory (Figure 1-3).

Other Foundation Design Issues

While saving energy may be the primaryreason for understanding good foundationdesign practices, there are other relatedbenefits. For example, insulating any type offoundation is likely to result in warmer floorsduring winter in above-grade spaces, thusimproving comfort as well as reducingenergy use. Insulating basement foundationscreates more comfortable conditions inbelow-grade space as well, making it moreusable for a variety of purposes at a relativelylow cost. Raising basement temperatures byusing insulation can also reducecondensation, thus minimizing problemswith mold and mildew.

In addition to energy conservation andthermal comfort, good foundation designmust be structurally sound, prevent waterand moisture problems, and control termitesand radon where appropriate. The

Figure 1-3: The impact of slab-on-grade foundation insulation is monitored in a test facility at OakRidge National Laboratory.


importance of these issues increases with anenergy-efficient design because there aresome potential problems caused by incorrectinsulating practices. Under certaincircumstances the structural integrity of afoundation can be negatively affected byinsulation when water control is notadequate. Without properly installing vaporbarriers and adequate air sealing, moisturecan degrade foundation insulation and othermoisture problems can actually be created.Improperly installed foundation insulationmay also provide entry paths for termites.Insulating and sealing a foundation to saveenergy results in a tighter building with lessinfiltration. If radon is present, it canaccumulate and reach higher levels in thebuilding than if greater outside air exchangewas occurring. All of these potential sideeffects can be avoided if recommendedpractices are followed.

1.2 Organization and Scopeof the Handbook

Residential foundations can beconstructed which reduce energyconsumption without creating health,moisture, radon, structural, or otherfoundation-related problems. The two basicpurposes of this handbook are (1) to providesimplified methods for estimating the site-specific energy savings and cost-effectivenessof foundation insulation measures, and (2) toprovide information and construction detailsconcerning thermal protection, subdrainage,waterproofing, structural requirements,radon control, and termite damageprevention.

Handbook Organization

The book is organized in a manner thatreflects the decision-making process used bya designer, builder, or homeowner dealingwith foundation design questions (see Figure1-4). First, one must determine thefoundation type and construction to be used.Then, if it is a basement foundation, it mustbe decided whether the below grade space beheated and/or cooled. These decisions aredetermined by regional, local, and site-specific factors as well as individual ormarket preference. Considerations related tochoosing a foundation type are discussed

Figure 1-4: Decision-Making Processfor Foundation Design

DETERMINE FOUNDATION TYPE: - BASEMENT - CRAWL SPACE - SLAB-ON-GRADE

DETERMINE USE OF BASEMENT:- HEATED / COOLED- UNCONDITIONED

DETERMINE CONSTRUCTION SYSTEM: - CONCRETE - MASONRY - WOOD

DETERMINE INSULATION PLACEMENT: - INTERIOR / EXTERIOR - VERTICAL / HORIZONTAL - WITHIN STRUCTURE (WOOD JOISTS OR STUDS)

DETERMINE AMOUNT OFINSULATION

FINALIZE CONSTRUCTION DOCUMENTS AND ESTABLISH QUALITY CONTROL INSPECTION PROCEDURES

DEVELOP CONSTRUCTION DETAILS: - INSULATION / THERMAL - STRUCTURAL - DRAINAGE AND WATERPROOFING - TERMITE CONTROL - RADON CONTROL


later in chapter 1. The first chapter alsoincludes introductory information on somegeneral concerns that pertain to allfoundation types.

After selecting a foundation type,proceed to the corresponding chapter:chapter 2 for basements, chapter 3 for crawlspaces, and chapter 4 for slab-on-gradefoundations. Each of these chapters isorganized into four parts. The first section ofeach chapter helps you select a cost-effectiveinsulation placement and amount for aparticular climate. The second sectionsummarizes general principles of structuraldesign, drainage and waterproofing, as wellas radon and termite control techniques. Thisis followed by a series of alternativeconstruction details illustrating theintegration of the major concerns involved infoundation design. These constructiondetails can be adapted to fit a unique site orbuilding condition. Within each constructiondrawing are labels that contain numberswithin boxes that refer to notes listed at theend of this section. Finally, the last section inchapters 2, 3, and 4 is a checklist to be usedduring design and construction.

Chapter 5 provides an alternativemethod for determining the cost-effectiveness of foundation insulation. In thefirst section of chapters 2, 3, and 4, insulationlevels are recommended for each foundationtype using a 30-year minimum life cycle costanalysis for several climatic regions in theUnited States. These are based on averageconstruction costs and representative energyprices for natural gas and electricity. Whilethese tables of recommendations are easy touse and provide good general guidelines,they cannot easily be adapted to reflect othercosts and conditions. Therefore, if theassumptions underlying the recommendedinsulation levels in chapters 2, 3, and 4 do notcorrespond to local conditions, it is stronglyrecommended that the user fill out theworksheet provided in chapter 5. Thisworksheet helps select the optimal level offoundation insulation for site-specific new orretrofit construction. Local energy prices andconstruction costs can be used in thecalculation, and economic decision criteriacan be chosen such as 20-year minimum lifecycle cost (suggested for retrofit) or 30-yearminimum life cycle cost (suggested for newconstruction).

Scope of the Handbook

The information presented in thishandbook pertains mostly to new residentialconstruction and small commercial buildings.The handbook covers all three basicfoundation types — basement, crawl space,and slab-on-grade. Conventional foundationsystems of cast-in-place concrete or concreteblock masonry are emphasized, althoughpressure-preservative-treated woodfoundations are also addressed.

The intention of this book is to providethe tools to help people make decisions aboutfoundation design. Often information existsrelated to a particular building material orproduct, but this book is one of the fewresources that attempts to address the overallintegration of a number of systems. Whilethis book does not provide exact constructiondocuments, specifications, and procedures, itprovides the basic framework andfundamental information needed to createthese documents.

Relation to the Previous Handbook

The information in this handbook isdrawn mainly from the Building FoundationDesign Handbook (Labs et al., 1988), a moreextensive technical reference manual onfoundation design. The original handbookwas intended for architects and engineers,while this handbook is intended to servebuilders. The first book explained not onlywhat to do in foundation design but alsomuch of the technical rationale behind therecommendations. This book presents whatto do in foundation design in a more conciseformat, and includes a few additions andimprovements to the original handbook.While the intended audience for this book isclearly home builders, the information ispertinent to anyone involved in foundationdesign and construction decisions includinghomeowners as well as architects andengineers looking for information in a moreconcise and updated form.

While this handbook does not include thetechnical reference information of the originalbook, notable additions to this version are: (1)the worksheet in chapter 5 which permitsenergy use calculations based on individualparameters, (2) simplified tables ofrecommended insulation levels in chapters 2,3, and 4, (3) distinct insulationrecommendations for several subcategoriesof insulation placement (i.e., interior, exterior,


ceiling, and within wall insulation forbasements), (4) construction practice noteslinked to the drawings, and (5) drawings thathave been revised or replaced. In spite ofthese improvements, the original BuildingFoundation Design Handbook represents avaluable resource for detailed technicalinformation not found in this book.

1.3 Foundation Type andConstruction System

The three basic types of foundations—full basement, crawl space, and slab-on-grade—are shown in Figure 1-5. Of course,actual houses may include combinations ofthese types. Information on a fourth type offoundation—the shallow or half-bermedbasement—can be found in the BuildingFoundation Design Handbook (Labs et al. 1988).

There are several construction systemsfrom which to choose for each foundationtype. The most common systems, cast-in-place concrete and concrete block foundationwalls, can be used for all four basicfoundation types. Other systems includepressure-preservative-treated woodfoundations, precast concrete foundationwalls, masonry or concrete piers, cast-in-place concrete sandwich panels, and variousmasonry systems. A slab-on-gradeconstruction with an integral concrete gradebeam at the slab edge is common in climateswith a shallow frost depth. In colderclimates, deeper cast-in-place concrete wallsand concrete block walls are more common,although a shallower footing can sometimesbe used depending on soil type, groundwaterconditions, and insulation placement.

Most of the foundation types andconstruction systems described above can bedesigned to meet necessary structural,thermal, radon, termite and moisture orwater control requirements. Factors affectingthe choice of foundation type andconstruction system include site conditions,overall building design, the climate, and localmarket preferences as well as constructioncosts. These factors are discussed below.

Site Conditions

The topography, water table location,presence of radon, soil type, and depth ofbedrock can all affect the choice of a

foundation type. Any foundation type can beused on a flat site; however, a sloping siteoften necessitates the use of a walkoutbasement or crawl space. On steeper slopes,a walkout basement combines a basementfoundation wall on the uphill side, a slab-on-grade foundation on the downhill side, andpartially bermed foundation walls on theremaining two sides.

A water table depth within 8 feet of thesurface will likely make a basementfoundation undesirable. Lowering the watertable with drainage and pumping usuallycannot be justified, and waterproofing maynot be feasible or may be too costly. A watertable near the surface generally restricts thedesign to a slab-on-grade or crawl spacefoundation.

The presence of expansive clay soils on asite requires special techniques to avoidfoundation movement and significantstructural damage. Often, buildings placedon sites with expansive clay require pilefoundations extending down to stable soilstrata or bedrock. Similarly, sites withbedrock near the surface require specialfoundation techniques. Expensive bedrockexcavation is not required to reach frostdepth nor is it economically justifiable tocreate basement space. In these unusualconditions of expansive clay soils or bedrocknear the surface, special variations of thetypical foundation types may be appropriate.

Overall Building Design

The foundation type and constructionsystem are chosen in part because ofappearance factors. Although it is notusually a major aesthetic element, thefoundation at the base of a building can beraised above the ground plane, so thefoundation wall materials can affect theoverall appearance. A building with a slab-on-grade foundation has little visiblefoundation; however, the foundation wall ofa crawl space or basement can varyconsiderably from almost no exposure to fullexposure above grade.

Climate

The preference of foundation type varieswith climatic region, although examples ofmost types can generally be found in anygiven region. One of the principal factorsbehind foundation preference is the impact offrost depth on foundation design. The


impact of frost depth basically arises from theneed to place foundations at greater depthsin colder climates. For example, a footing inMinnesota must be at least 42 inches belowthe surface, while in states along the GulfCoast, footings need not extend below thesurface at all in order to avoid structuraldamage from frost heave. Because afoundation wall extending to a substantialdepth is required in northern climates, theincremental cost of creating basement spaceis much less, since it is necessary to buildapproximately half the basement wallanyway. In a southern climate theincremental first cost of creating a basementis greater when compared with a slab-on-grade with no significant required footingdepth.

This historic perception that foundationsmust extend below the natural frost depth isnot entirely accurate. Buildings with veryshallow foundations can be used in coldclimates if they are insulated properly.

Local Market Preferences andConstruction Costs

The foundation type and constructionsystem are also chosen based on cost andmarket factors that vary regionally or evenlocally. Virtually any foundation type andconstruction system can be built in anylocation in the United States. The relativecosts, however, are likely to differ. Thesecosts reflect local material and labor costs aswell as the availability of certain materialsand the preferences of local contractors. Forexample, in certain regions there are manycontractors specializing in cast-in-placeconcrete foundation walls. Because theyhave the concrete forms and the requiredexperience with this system and becausebidding is very competitive, this system maybe more cost-effective compared with otheralternatives. In other regions, the availabilityof concrete blocks is greater and there aremany contractors specializing in masonryfoundation walls. In these areas, a cast-in-place concrete system may be lesscompetitive economically because fewercontractors are available.

More subjective factors that influence adesigner’s choice of foundation type andconstruction system are the expectations andpreferences of individual clients and thehome-buying public. These marketinfluences are based not only on cost but alsoon the area’s tradition. If people in a certain

region expect basements, then buildersgenerally provide them. Of course,analyzing the cost-effectiveness of providinga basement requires a somewhat subjectivejudgment concerning the value of basementspace. These more subjective market factorsand regional preferences tend to increase theavailability of materials and contractors forthe preferred systems, which in turn makesthese systems more cost-effective choices.

C: SLAB-ON-GRADE

B: CRAWL SPACE

A: DEEP BASEMENT

Figure 1-5: Basic Foundation Types


1.4 Radon MitigationTechniques

In this introductory chapter radon isaddressed because it is a relatively newconcern and one in which techniques to dealwith it are just emerging.

Radon is a colorless, odorless, tastelessgas found in soils and underground water.An element with an atomic weight of 222,radon is produced in the natural decay ofradium, and exists at varying levelsthroughout the United States. Radon isemitted from the ground to the outdoor air,where it is diluted to an insignificant level bythe atmosphere. Because radon is a gas, itcan travel through the soil and into abuilding through cracks, joints, and otheropenings in the foundation floor and wall.Earth-based building materials such as castconcrete, concrete masonry, brick, and adobeordinarily are not significant sources of

indoor radon. Radon from well watersometimes contributes in a minor way toradon levels in indoor air. In a few cases,radon from well water has contributedsignificantly to elevated radon levels.

Health Risk of Radon Exposure

Radon is potentially harmful only if it isin the lungs when it decays into otherisotopes (called radon progeny or radondaughters), and when these further decay.The decay process releases small amounts ofionizing radiation; this radiation is heldresponsible for the above-normal incidence oflung cancer found among miners. Most ofwhat is known about the risk of radonexposure is based on statistical analysis oflung cancers in humans (specifically,underground miners) associated withexposure to radon. This information is welldocumented internationally, although muchless is known about the risk of long-term

CRACKS IN BELOW-GRADE WALLS

CONSTRUCTIONJOINT AT SLAB EDGE

GAPS AROUND SERVICE PIPES CAVITIES IN

MASONRY WALLS

GAPS IN SUSPENDED FLOORS

CRACKS IN WALLS

CRACKS IN FLOOR SLABS

Figure 1-6: Points of Radon Entry into Buildings


exposure to low concentrations of radon inbuildings.

The lung cancer hazard due to radon is afunction of the number of radioactive decayevents that occur in the lungs. This is relatedto both intensity and duration of exposure toradon gas and decay products plus theequilibrium ratio. Exposure to a low level ofradon over a period of many years in onebuilding can present the same health hazardas exposure to a higher level of radon for ashorter period of time in another building.The sum of all exposures over the course ofone's life determines the overall risk to thatindividual.

Strategies to Control Radon

As a national policy, the public has beenurged by the Environmental ProtectionAgency to consider 4 pCi/L (from long-termradon tests) as an “action level” for both newand existing buildings (EPA 1987). TheASHRAE Standard 62-1989, Ventilation forAcceptable Indoor Air Quality, has alsorecognized this value as a guideline(ASHRAE 1989).

In order to address the radon problem, itis necessary to find out to what degree it ispresent on the site. Then, depending on thelevel of concern, various techniques tocontrol radon levels can be applied.Generally there are three approaches: (1) thebarrier approach, (2) soil gas interception,and (3) indoor air management. The barrierapproach refers to a set of techniques forconstructing a tight building foundation inorder to prevent soil gas from entering. Sincethe barrier approach differs for eachfoundation type, these techniques aredescribed in chapters 2, 3, and 4 as theyapply to basements, crawl spaces, and slab-on-grade foundations. Intercepting soil gasrefers to using vent pipes and fans to drawsoil gas from a gravel layer beneath thefoundation floor slab. Since this approachcan be utilized for basements and slab-on-grade foundations, it is described in detail inchapters 2 and 4. The third generalapproach—managing indoor air—applies toall foundation types and is described below.

Managing Indoor Air

Air management techniques may be usedto minimize the suction applied to thesurrounding soil gas by the building. Tocontrol the pressure differential across the

envelope, it is desirable to make the entirebuilding envelope airtight and control theamount of incoming fresh air, exhaustedinside air, and supply air for combustiondevices. A passive house with no mechanicalfans operating at any given condition has aneutral pressure plane where no pressuredifferential exists across the buildingenvelope. Envelope cracks above this planeexfiltrate and openings below infiltrate.

The principles applied to minimizepressure differences across the buildingfoundation envelope are essentially the sameas those recommended for moisture vaporcontrol and energy-efficient design. Theseinclude the following:

1. Reduce air infiltration from theunconditioned spaces (crawl spaces, attics,and unconditioned basements) into theoccupied space by sealing openings andcracks between the two, including flues, ventstacks, attic hatchways, plumbing, wiring,and duct openings.

2. Consider locating the attic accessoutside conditioned space (for example, anattached garage).

3. Seal all openings in top and bottomplates of frame construction, includinginterior partitions.

4. Provide separate outdoor air intakesfor combustion equipment.

5. Install an air barrier in all above-gradeexterior walls.

6. Adjust ventilation systems to helpneutralize imbalances between indoor andoutdoor air pressures. Keeping a houseunder continuous slight positive pressure is adifficult technique to accomplish. At thistime whole house, basement, or crawl spacepressurization does not appear to be a viablesolution to radon control.

7. Do not locate return air ducts in acrawl space or beneath a slab. Placing theHVAC ducting inside the conditioned spacewill save energy as well.

8. Do not locate supply ducts belowconcrete slabs on or below grade.

9. Seal all return ductwork located incrawl spaces.

10. Balance the HVAC ducts. Systemimbalance can lead to pressurization in somezones and depressurization in others.

Chapter 2—Basement Construction

This chapter summarizes suggestedpractices related to basements. Section 2.1presents recommended optimal levels ofinsulation. Recommendations are given fortwo distinct basement conditions: (1) a fullyconditioned (heated and cooled) deepbasement, and (2) an unconditioned deepbasement.

Section 2.2 contains a brief summary ofbasement design practices and coversstructural design, location of insulation,drainage and waterproofing, termite andwood decay control, and radon control.Section 2.3 includes a series of alternativeconstruction details with accompanyingnotes indicating specific practices. Section 2.4is a checklist to be used during the design,construction, and site inspection of abasement.

2.1 Basement InsulationPlacement and Thickness

The term deep basement refers to a 7- to10-foot basement wall with no more than theupper 25 percent exposed above grade. Fullyconditioned means that the basement isheated and cooled to set thermostat levelssimilar to typical above-grade spaces: at least70OF during the heating season, and nohigher than 78OF during the cooling season.

The unconditioned deep basement isidentical to the conditioned deep basementdescribed previously except that the space isnot directly heated or cooled to maintain atemperature in the 70OF to 78OF range.Instead, it is assumed that the basementtemperature fluctuates during the year basedFigure 2-1: Concrete Masonry Basement Wall

with Exterior Insulation

CHAPTER 2

Basement Construction


configurations shown in Tables 2-1 and 2-2,the case with the lowest 30-year life cycle costwas determined for five U.S. cities at threedifferent fuel cost levels. See the BuildingFoundation Design Handbook (Labs et al. 1988)to find recommendations for a greaternumber of cities and for a detailedexplanation of the methodology. Theeconomic methodology used to determinethe insulation levels in Tables 2-1 and 2-2 isconsistent with ASHRAE standard 90.2P.The simple payback averages 13 years for allU.S. climate zones, and never exceeds 18years for any of the recommended levels.

Economically optimal configurations areshown by the darkened circles in Tables 2-1and 2-2 in the following categories:(1) concrete/masonry wall with exteriorinsulation, (2) concrete/masonry wall withinterior insulation without including the costfor interior finish material, (3) concrete/masonry wall with interior insulation whichincludes the cost for sheetrock, (4) pressure-preservative-treated wood wall insulation,and (5) ceiling insulation (shown only inTable 2-2). Configurations are recommendedfor a range of climates and fuel prices in eachof these categories, but the differentcategories of cases are not directly comparedwith each other. In other words, there is anoptimal amount of exterior insulationrecommended for a given climate and fuelprice, and there is a different optimal amountof insulation for interior insulation withsheetrock. Where there is no darkened circlein a particular category, insulation is noteconomically justified under the assumptionsused.

Fully Conditioned Basements

For fully conditioned basements withconcrete/masonry walls, exterior insulationis justified at three fuel price levels (shown inTable 2-3) in all climate zones except thewarmest one, which includes cities such asLos Angeles and Miami. In most locations R-10 insulation or greater covering the entirewall on the exterior is justified with a fullyconditioned basement. For interiorinsulation even higher levels of insulation aregenerally recommended ranging from R-11to R-19 in most cases. Whether or notsheetrock is included in the cost ofinstallation appears to have relatively littleimpact on the recommendations. Forpressure-preservative-treated wood walls, R-19 insulation is justified in almost all

on heat transfer between the basement andvarious other heat sources and sinksincluding (1) the above-grade space, (2) thesurrounding soil, and (3) the furnace andducts within the basement. Generally, thetemperature of the unconditioned spaceranges between 55OF and 70OF most of theyear in most climates.

Insulation Configurations

Tables 2-1 and 2-2 include illustrationsand descriptions of a variety of basementinsulation configurations. Two basicconstruction systems are shown—a concrete(or masonry) basement wall and a pressure-preservative-treated wood basement wall.

For conditioned basements, shown inTable 2-1, there are three general approachesto insulating the concrete/masonry wall: (1)on the exterior covering the upper half of thewall, (2) on the exterior covering the entirewall, and (3) on the interior covering theentire wall. With pressure-preservative-treated wood construction, mineral wool battinsulation is placed in the cavities betweenthe wood studs.

Table 2-2, which addressesunconditioned basements, includes the sameset of configurations used in Table 2-1 as wellas three additional cases where insulation isplaced between the floor joists in the ceilingabove the unconditioned basement. Thisapproach thermally separates the basementfrom the above-grade space, resulting inlower basement temperatures in winter andusually necessitating insulation of exposedducts and pipes in the basement. Basementceiling insulation can be applied with eitherconstruction system — concrete/masonry orwood basement walls — but is mostcommonly used with concrete/masonryfoundations.

Recommended Insulation Levels

While increasing the amount of basementinsulation produces greater energy savings,the cost of installation must be compared tothese savings. Such a comparison can bedone in several ways; however, a life cyclecost analysis presented in worksheet form inchapter 5 is recommended. It takes intoaccount a number of economic variablesincluding installation costs, mortgage rates,HVAC efficiencies, and fuel escalation rates.In order to identify the most economicalamount of insulation for the basement


Table 2-1: Insulation Recommendations for Fully Conditioned Deep Basements

CONFIGURATION DESCRIPTION 0-2000 HDD(LOS ANG)

2-4000 HDD(FT WORTH)

4-6000 HDD(KAN CITY)

6-8000 HDD(CHICAGO)

8-10000 HDD(MPLS)

EXTERIOR: HALF WALL

EXTERIOR: FULL WALL

INTERIOR: FULL WALL

WOOD: FULL WALL

A: Concrete or Masonry Foundation Walls with Exterior Insulation

D: Pressure-Treated Wood Foundation Walls

NO INSULATION

8 FT: R-6 RIGID

8 FT: R-8 RIGID

8 FT: R-11 BATT

8 FT: R-19 BATT

8 FT: R-5 RIGID

8 FT: R-10 RIGID

8 FT: R-15 RIGID

8 FT: R-20 RIGID

NO INSULATION

4 FT: R-5 RIGID

4 FT: R-10 RIGID

NO INSULATION

8 FT: R-11 BATT

8 FT: R-19 BATT

8 FT: R-30 BATT

RECOMMENDED CONFIGURATIONS AT THREE FUEL PRICE LEVELS

L M H L M H L M H L M H L M H

B: Concrete or Masonry Foundation Walls with Interior Insulation (Costs do not include interior finish material)

INTERIOR: FULL WALLNO INSULATION

8 FT: R-6 RIGID

8 FT: R-8 RIGID

8 FT: R-11 BATT

8 FT: R-19 BATT

C: Concrete or Masonry Foundation Walls with Interior Insulation (Costs include sheetrock on interior wall)

1. L, H, and M refer to the low, medium, and high fuel cost levels indicated in Table 2-3.2. The darkened circle represents the recommended level of insulation in each column for each of the four basic insulation configurations.3. These recommendations are based on assumptions that are summarized at the end of section 2.1 and further explained in chapter 5.


Table 2-2: Insulation Recommendations for Unconditioned Deep Basements


CONFIGURATION DESCRIPTION 0-2000 HDD(LOS ANG)



6-8000 HDD(CHICAGO)

8-10000 HDD(MPLS)

EXTERIOR: HALF WALL

EXTERIOR: FULL WALL

INTERIOR: FULL WALL

WOOD: FULL WALL



NO INSULATION

8 FT: R-6 RIGID

8 FT: R-8 RIGID

8 FT: R-11 BATT

8 FT: R-19 BATT

8 FT: R-5 RIGID

8 FT: R-10 RIGID

8 FT: R-15 RIGID

8 FT: R-20 RIGID

NO INSULATION

4 FT: R-5 RIGID

4 FT: R-10 RIGID

NO INSULATION

8 FT: R-11 BATT

8 FT: R-19 BATT

8 FT: R-30 BATT




CEILING

E: Concrete or Masonry Foundation Walls with Ceiling Insulation

NO INSULATION

R-11 BATT

R-19 BATT

R-30 BATT

INTERIOR: FULL WALLNO INSULATION

8 FT: R-6 RIGID

8 FT: R-8 RIGID

8 FT: R-11 BATT

8 FT: R-19 BATT



locations at all fuel price levels. This is due tothe low initial cost of installing insulationwithin the available stud cavity of the woodfoundation.

Unconditioned Basements

Compared with recommended insulationlevels for fully conditioned basements, lowerlevels are economically justified inunconditioned basements in most locationsdue to generally lower basementtemperatures. For concrete/masonry wallswith exterior insulation, R-5 insulation on theupper wall is justified only in the colderclimates at low (L) and medium (M) fuelprices. At the high fuel price level (H), R-5insulation on the upper wall is justified inmoderate climates, while R-10 insulation onthe entire wall is recommended in the coldestcities. For interior insulation withoutsheetrock, R-11 is recommended in moderateto cold climates at all fuel price levels.Including the cost of sheetrock, however,reduces the number of cases where interiorinsulation is economically justified. Forbasements with pressure-preservative-treated wood walls, R-11 to R-19 insulation isjustified in moderate to cold climates. Whenceiling insulation is placed over anunconditioned basement, R-30 insulation isjustified in colder cities and some insulationis justified in most cities.

Comparison of Insulation Systems

Generally, insulating pressure-preservative-treated wood walls is more cost-effective than insulating concrete/masonrywalls to an equivalent level. This is becausethe cavity exists between studs in a woodwall system and the incremental cost ofinstalling batt insulation in these cavities is

relatively low. Thus, a higher R-value iseconomically justified for wood wall systems.

On concrete/masonry basement walls,interior insulation is generally more cost-effective than an equivalent amount ofexterior insulation. This is because the laborand material costs for rigid insulation withprotective covering required for an exteriorinstallation typically exceed the cost ofinterior insulation. Even though the cost ofstuds and sheetrock may be included in aninterior installation, the incremental cost ofbatt installation is relatively little. If rigidinsulation is used in an interior application,the installation cost is less than placing it onthe exterior. Because it does not have towithstand exposure to water and soilpressure below grade as it does on theexterior, a less expensive material can beused. Costs are further reduced since interiorinsulation does not require a protectiveflashing or coating to prevent degradationfrom ultraviolet light as well as mechanicaldeterioration.

Insulating the ceiling of anunconditioned basement is generally morecost-effective than insulating the walls of anunconditioned basement to an equivalentlevel. This is because placing batt insulationinto the existing spaces between floor joistsrepresents a much smaller incremental costthan placing insulation on the walls. Thushigher levels of ceiling insulation can beeconomically justified when compared towall insulation.

In spite of the apparent energy efficiencyof wood versus concrete/masonry basementwalls, this is only one of many cost andperformance issues to be considered.Likewise, on a concrete/masonry foundationwall, the economic benefit of interior versusexterior insulation may be offset by otherpractical, performance, and aesthetic

Table 2-3: Fuel Price Levels Used to Develop Recommended Insulation Levels in Tables 2-1 and 2-2

SEASON FUEL TYPE LOW PRICE LEVEL ($) MEDIUM PRICE LEVEL ($) HIGH PRICE LEVEL ($)

NATURAL GAS

FUEL OIL

PROPANE

HEATING

COOLING ELECTRICITY

.374 / THERM

.527 / GALLON

.344 / GALLON

.051 / KWH

.561 / THERM

.791 / GALLON

.516 / GALLON

.076 / KWH

.842 / THERM

1.187 / GALLON

.775 / GALLON

.114 / KWH


considerations discussed elsewhere in thisbook. Although ceiling insulation in anunconditioned basement appears more cost-effective than wall insulation, this approachmay be undesirable in colder climates sincepipes and ducts may be exposed to freezingtemperatures and the space will be unusablefor many purposes. In all cases the choice offoundation type and insulation system mustbe based on many factors in addition toenergy cost-effectiveness.

Assumptions

These general recommendations arebased on a set of underlying assumptions.Fuel price assumptions used in this analysisare shown in Table 2-3. The total heatingsystem efficiency is 68 percent and thecooling system SEER is 9.2 with 10 percentduct losses. Energy price inflation andmortgage conditions are selected to allowmaximum simple payback of 18 years withaverage paybacks of about 13 years.

The total installed costs for all insulationsystems considered in this analysis areshown in Table 5-2 in chapter 5. Installationcosts used in this analysis are based onaverage U.S. costs in 1987. For the exteriorcases, costs include labor and materials forextruded polystyrene insulation and therequired protective covering and flashingabove grade. For the interior cases, costsinclude labor and materials for expandedpolystyrene (R-6 and R-8) and wood framingwith fiberglass batts (R-11 and R-19). Theinstalled costs and R-values for all interior

cases are shown with and without interiorfinish material. All costs include a 30 percentbuilder markup and a 30 percentsubcontractor markup for overhead andprofit.

With pressure-preservative-treated woodconstruction, batt insulation is placed in thecavities between the wood studs. Costs usedin the analysis reflect only the additional costof installing the insulation, not the interiorfinish which might be used with or withoutinsulation. A higher cost increment is usedwhen R-30 insulation is placed in a woodwall reflecting the additional depth requiredin the studs.

If the general assumptions used in thisanalysis are satisfactory for the specificproject, the reader can determine theapproximate recommended insulation levelfor a location by finding the heating degreedays from Table 5-1 in chapter 5 andselecting the appropriate climate zone andfuel price level shown in Tables 2-1 and 2-2.If not, project-specific optimal insulationlevels can be determined using actualestimated construction costs with theworksheet provided in chapter 5. Theworksheet enables the user to select economiccriteria other than allowing maximum simplepaybacks of 18 years. In addition the usercan incorporate local energy prices, actualinsulation costs, HVAC efficiencies, mortgageconditions, and fuel escalation rates. Cost-effectiveness can vary considerably,depending on the construction details andcost assumptions.


ANCHOR BOLT CONNECTSFOUNDATION WALL TOSUPERSTRUCTURE ANDRESISTS WIND UPLIFT

WALL RESISTS VERTICAL LOAD FROM ABOVE-GRADE STRUCTURE

SPREAD FOOTING DISTRIBUTES VERTICALLOAD TO GROUND

SLAB SUPPORTS FLOOR LOAD FROM BASEMENT

WALL RESISTS LATERAL LOADFROM SOIL

2.2 Recommended Designand Construction Details

STRUCTURAL DESIGN

The major structural components of abasement are the wall, the footing, and thefloor (see Figure 2-2). Basement walls aretypically constructed of cast-in-placeconcrete, concrete masonry units, orpressure-preservative-treated wood.Basement walls must be designed to resistlateral loads from the soil and vertical loadsfrom the structure above. The lateral loadson the wall depend on the height of the fill,the soil type, soil moisture content, andwhether the building is located in an area oflow or high seismic activity. Some simpleguidelines for wall thickness, concretestrength, and reinforcing are given in theconstruction details that follow. Wheresimple limits are exceeded, a structuralengineer should be consulted.

Concrete spread footings providesupport beneath basement concrete andmasonry walls and columns. Footings mustbe designed with adequate size to distributethe load to the soil. Unless founded onbedrock or proven non-frost-susceptible soils,footings must be placed beneath themaximum frost penetration depth or beinsulated to prevent frost penetration. Acompacted gravel bed serves as the footingunder a wood foundation wall whendesigned in accordance with the NationalForest Products Association’s woodfoundations design specifications (NFPA1987).

Concrete slab-on-grade floors aregenerally designed to have sufficient strengthto support floor loads without reinforcingwhen poured on undisturbed or compactedsoil. The use of welded wire fabric andconcrete with a low water/cement ratio canreduce shrinkage cracking, which is animportant concern for appearance and forreducing potential radon infiltration.

Where expansive soils are present or inareas of high seismic activity, specialfoundation construction techniques may benecessary. In these cases, consultation withlocal building officials and a structuralengineer is recommended.

Figure 2-2: Components of Basement Structural System


DRAINAGE ANDWATERPROOFING

Keeping water out of basements is amajor concern in many regions. The sourceof water is primarily from rainfall, snowmelt, and sometimes irrigation on thesurface. In some cases, the groundwatertable is near or above the basement floor levelat times during the year. There are threebasic lines of defense against water problemsin basements: (1) surface drainage, (2)subsurface drainage, and (3) dampproofingor waterproofing on the wall surface (seeFigure 2-3).

The goal of surface drainage is to keepwater from surface sources away from thefoundation by sloping the ground surfaceand using gutters and downspouts for roofdrainage. The goal of subsurface drainage isto intercept, collect, and carry away anywater in the ground surrounding thebasement. Components of a subsurfacesystem can include porous backfill, drainagemat materials or insulated drainage boards,and perforated drainpipes in a gravel bedalong the footing or beneath the slab thatdrain to a sump or to daylight. Localconditions will determine which of thesesubsurface drainage system components, ifany, are recommended for a particular site.

The final line of defense—waterproofing—is intended to keep outwater that finds its way to the wall of thestructure. First, it is important to distinguishbetween the need for dampproofing versuswaterproofing. In most cases a dampproofcoating covered by a 4-mil layer ofpolyethylene is recommended to reducevapor and capillary draw transmission fromthe soil through the basement wall. Adampproof coating, however, is not effectivein preventing water from entering throughthe wall. Waterproofing is recommended (1)on sites with anticipated water problems orpoor drainage, (2) when finished basementspace is planned, or (3) on any foundationbuilt where intermittent hydrostatic pressureoccurs against the basement wall due torainfall, irrigation, or snow melt. On siteswhere the basement floor could be below thewater table, a crawl space or slab-on-gradefoundation is recommended.

Figure 2-3: Components of Basement Drainage andWaterproofing Systems

1. SURFACE DRAINAGE SYSTEM COMPONENTS - SLOPE GROUND AWAY - IMPERMEABLE TOPSOIL - GUTTERS AND DOWNSPOUTS

2. SUBSURFACE DRAINAGE SYSTEM COMPONENTS - POROUS BACKFILL OR DRAINAGE MAT - DRAIN PIPES IN GRAVEL BED ALONG FOOTING - GRAVEL LAYER UNDER FLOOR SLAB - PIPES DRAIN TO A SUMP OR DAYLIGHT

3. DAMPPROOFING OR WATERPROOFING SYSTEM COMPONENTS - MATERIAL APPLIED DIRECTLY TO WALL EXTERIOR - PROTECTION BOARD OFTEN REQUIRED


LOCATION OF INSULATION

A key question in foundation design iswhether to place insulation inside or outsidethe basement wall. In terms of energy use,there is not a significant difference betweenthe same amount of full wall insulationapplied to the exterior versus the interior of aconcrete or masonry wall. However, theinstallation costs, ease of application,appearance, and various technical concernscan be quite different. Individual designconsiderations as well as local costs andpractices determine the best approach foreach project.

Rigid insulation placed on the exteriorsurface of a concrete or masonry basementwall has some advantages over interiorplacement in that it (1) can providecontinuous insulation with no thermalbridges, (2) protects and maintains thewaterproofing and structural wall atmoderate temperatures, (3) minimizesmoisture condensation problems, and (4)does not reduce interior basement floor area.Exterior insulation at the rim joist leavesjoists and sill plates open to inspection fromthe interior for termites and decay. On theother hand, exterior insulation on the wallcan provide a path for termites if not treatedadequately and can prevent inspection of thewall from the exterior.

Interior insulation is an effectivealternative to exterior insulation. Interiorinsulation placement is generally lessexpensive than exterior placement if the costof the interior finish materials is not included.However, this does not leave the wall with afinished, durable surface. Energy savingsmay be reduced with some systems anddetails due to thermal bridges. For example,partial interior wall insulation is notrecommended because of the possiblecircumventing of the insulation through thewall construction. Insulation can be placedon the inside of the rim joist but with greaterrisk of condensation problems and less accessto wood joists and sills for termite inspectionfrom the interior.

Insulation placement in the basementceiling of an unconditioned basement isanother acceptable alternative. Thisapproach is relatively low in cost andprovides significant energy savings.However, ceiling insulation should be usedwith caution in colder climates where pipesmay freeze and structural damage may resultfrom lowering the frost depth.

With a wood foundation system,insulation is placed in the stud cavitiessimilarly to insulation in an above-gradewood frame wall. A 2-inch air space shouldbe provided between the end of theinsulation and the bottom plate of thefoundation wall. This approach has arelatively low cost and provides sufficientspace for considerable insulation thickness.

In addition to more conventional interioror exterior placement covered in thishandbook, there are several systems thatincorporate insulation into the constructionof the concrete or masonry walls. Theseinclude (1) rigid foam plastic insulation castwithin a concrete wall, (2) polystyrene beadsor granular insulation materials poured intothe cavities of conventional masonry walls,(3) systems of concrete blocks with insulatingfoam inserts, (4) formed, interlocking rigidfoam units that serve as a permanent,insulating form for cast-in-place concrete,and (5) masonry blocks made withpolystyrene beads instead of aggregate in theconcrete mixture, resulting in significantlyhigher R-values. However, the effectivenessof systems that insulate only a portion of thewall area should be evaluated closely becausethermal bridges through the insulation canimpact the total performance significantly.

TERMITE AND WOOD DECAYCONTROL TECHNIQUES

Techniques for controlling the entry oftermites through residential foundations areadvisable in much of the United States (seeFigure 2-4). The following recommendationsapply where termites are a potential problem.Consult with local building officials andcodes for further details.

1. Minimize soil moisture around thebasement by using gutters, downspouts, andrunouts to remove roof water, and byinstalling a complete subdrainage systemaround the foundation.

2. Remove all roots, stumps, and scrapwood from the site before, during, and afterconstruction, including wood stakes andformwork from the foundation area.

3. Treat soil with termiticide on all sitesvulnerable to termites.

4. Place a bond beam or course of capblocks on top of all concrete masonryfoundation walls to ensure that no open cores


are left exposed. Alternatively, fill all coreson the top course with mortar, and reinforcethe mortar joint beneath the top course.

5. Place the sill plate at least 8 inchesabove grade; it should be pressure-preservative treated to resist decay. The sillplate should be visible for inspection fromthe interior. Since termite shields are oftendamaged or not installed carefully enough,they are considered optional and should notbe regarded as sufficient defense bythemselves.

6. Be sure that exterior wood siding andtrim is at least 6 inches above grade.

7. Construct porches and exterior slabs sothat they slope away from the foundationwall, and are at least 2 inches below exteriorsiding. In addition, porches and exteriorslabs should be separated from all woodmembers by a 2-inch gap visible forinspection or by a continuous metal flashingsoldered at all seams.

8. Fill the joint between the slab floor andfoundation wall with urethane caulk or coaltar pitch to form a termite barrier.

9. Use pressure-preservative-treatedwood posts on the basement floor slab, orplace posts on flashing or a concrete pedestalraised 1 inch above the floor.

10. Flash hollow steel columns at the topto stop termites. Solid steel bearing platescan also serve as a termite shield at the top ofa wood post or hollow steel column.

Plastic foam and mineral wool insulationmaterials have no food value to termites, butthey can provide protective cover and easytunnelling. Insulation installations can bedetailed for ease of inspection, although oftenby sacrificing thermal efficiency. In principle,termite shields offer protection, but shouldnot be relied upon as a barrier.

These concerns over insulation and theunreliability of termite shields have led to theconclusion that soil treatment is the mosteffective technique to control termites withan insulated foundation. However, therestrictions on widely used termiticides maymake this option either unavailable or causethe substitution of products that are moreexpensive and possibly less effective. Thissituation should encourage insulationtechniques that enhance visual inspectionand provide effective barriers to termites.

Figure 2-4: Termite Control Techniques for Basements

PRESSURE-PRESERVATIVETREATED SILL PLATE8-IN. MIN. ABOVE GRADE

WOOD SIDING 6-IN. MIN.ABOVE GRADE

REMOVE ROOTS, TRUNKS,AND SCRAP WOOD FROMFOUNDATION AREA

MINIMIZE SOIL MOISTURE - USE GUTTERS AND DOWNSPOUTS - INSTALL SUBSURFACE DRAINAGE SYSTEM

TREAT SOIL FOR TERMITES

BOND BEAM, CAP BLOCK,OR FILLED UPPER COURSE OF MASONRY WALL

FILL JOINT WITHCAULKING

WOOD POSTS SHOULD BETREATED OR PLACED ON A 1-IN. PEDESTAL

PLACE FLASHING OVER HOLLOW METAL POSTS


RADON CONTROL TECHNIQUES

Construction techniques for minimizingradon infiltration into the basement areappropriate where there is a reasonableprobability that radon may be present (seeFigure 2-5). To determine this, contact thestate health department or environmentalprotection office. General approaches tominimizing radon include (1) sealing joints,cracks, and penetrations in the foundation,and (2) evacuating soil gas surrounding thebasement.

Sealing the Basement Floor

1. Use solid pipes for floor dischargedrains to daylight, or mechanical traps thatdischarge to subsurface drains.

2. Use a 6-mil (minimum) polyethylenefilm beneath the slab on top of the graveldrainage bed. This film serves as a radonand moisture retarder and also preventsconcrete from infiltrating the aggregate baseunder the slab as it is cast. Slit an “x” in thepolyethylene membrane to receivepenetrations. Turn up the tabs and tapethem. Care should be taken to avoidunintentionally puncturing the barrier;consider using rounded riverbed gravel ifpossible. The riverbed gravel allows for freermovement of the soil gas and also offers nosharp edges to penetrate the polyethylene.The edges of the film should be lapped atleast 12 inches. The polyethylene shouldextend over the top of the footing, or besealed to the foundation wall. A 2-inch-thicksand layer on top of the polyethyleneimproves concrete curing and offers someprotection from puncture of the polyethyleneduring the concrete pouring operation.

3. Tool the joint between the wall andslab floor and seal with polyurethane caulk,which adheres well to concrete and is long-lasting.

4. Avoid perimeter gutters around theslab that provide a direct opening to the soilbeneath the slab.

5. Minimize shrinkage cracking bykeeping the water content of the concrete aslow as possible. If necessary, use plasticizers,not water, to increase workability.

6. Reinforce the slab with wire mesh orfibers to reduce shrinkage cracking,especially near the inside corner of “L”shaped slabs.

PARGE MASONRY WALL

INSTALL DRAINAGE BOARD TO PROVIDE ESCAPE FOR SOIL GAS

DAMPPROOFING ORWATERPROOFING

SOLID BLOCK OR FILLLOWER COURSE SOLID

BOND BEAM, CAP BLOCK,OR FILLED UPPER COURSE OF MASONRY WALL

SEAL AROUND ALL DOORS, DUCTS OR PIPES IN WALLS,FLOORS, OR LEADING TO ADJACENT CRAWL SPACES

USE SOLID DRAINPIPES INFLOOR WITH MECHANICALTRAPS

POLYURETHANECAULKING IN JOINT

REINFORCE SLAB AND USE CONCRETE WITH LOW WATER/CEMENT RATIO TO REDUCE CRACKING

6-MIL POLY LAYERUNDER SLABSEALED TO WALL

REINFORCE WALLS AND FOOTING TO MINIMIZECRACKING

Figure 2-5: Radon Control Techniques for Basements


3. Parge and seal the exterior face ofbelow-grade concrete masonry walls incontact with the soil. Install drainage boardsto provide an airway for soil gas to reach thesurface outside the wall rather than beingdrawn through the wall.

4. Install a continuous dampproofing orwaterproofing membrane on the exterior ofthe wall. Six-mil polyethylene placed on theexterior of the basement wall surface willretard radon entry through wall cracks.

5. Seal around plumbing and other utilityand service penetrations through the wallwith polyurethane or similar caulking. Boththe exterior and the interior of concretemasonry walls should be sealed atpenetrations.

6. Install airtight seals on doors and otheropenings between a basement and adjoiningcrawl space.

7. Seal around ducts, plumbing, andother service connections between abasement and a crawl space.

Intercepting Soil Gas

At this time the best strategy formitigating radon hazard seems to be toreduce stack effects by building a tightfoundation in combination with a generallytight above-grade structure, and to make surea radon collection system and, at the veryleast, provisions for a discharge system arean integral part of the initial construction.This acts as an insurance policy at modestcost. Once the house is built, if radon levelsare excessive, a passive discharge system canbe connected and if further mitigation effortis needed, the system can be activated byinstalling an in-line duct fan (see Figure 2-6).

Subslab depressurization has proven tobe an effective technique for reducing radonconcentrations to acceptable levels, even inhomes with extremely high concentrations(Dudney 1988). This technique lowers thepressure around the foundation envelope,causing the soil gas to be routed into acollection system, avoiding the inside spacesand discharging to the outdoors. This systemcould be installed in two phases. The firstphase is the collection system located on thesoil side of the foundation, which should beinstalled during construction. The collectionsystem, which may consist of nothing morethan 4 inches of gravel beneath the slab floor,can be installed at little or no additional cost

7. Where used, finish control joints with a1/2-inch depression and fully fill this recesswith polyurethane or similar caulk.

8. Minimize the number of pours toavoid cold joints. Begin curing the concreteimmediately after the pour, according torecommendations of the American ConcreteInstitute (1980; 1983). At least three days arerequired at 70OF, and longer at lowertemperatures. Use an impervious cover sheetor wetted burlap to facilitate curing. TheNational Ready Mix Concrete Associationsuggests a pigmented curing compoundshould also be used.

9. Form a gap of at least 1/2-inch widtharound all plumbing and utility lead-insthrough the slab to a depth of at least 1/2inch. Fill with polyurethane or similarcaulking.

10. Do not install sumps withinbasements in radon-prone areas unlessabsolutely necessary. Where used, cover thesump pit with a sealed lid and vent to theoutdoors. Use submersible pumps.

11. Install mechanical traps at allnecessary floor drains discharging throughthe gravel beneath the slab.

12. Place HVAC condensate drains sothat they drain to daylight outside of thebuilding envelope. Condensate drains thatconnect to dry wells or other soil maybecome direct paths for soil gas, and can be amajor entry point for radon.

13. Seal openings around water closets,tub traps, and other plumbing fixtures(consider nonshrinkable grout).

Sealing the Basement Walls

1. Reinforce walls and footings tominimize shrinkage cracking and crackingdue to uneven settlement.

2. To retard movement of radon throughhollow core masonry walls, the top andbottom courses of hollow masonry wallsshould be solid block, or filled solid. If thetop side of the bottom course is below thelevel of the slab, the course of block at theintersection of the bottom of the slab shouldbe filled. Where a brick veneer or othermasonry ledge is installed, the courseimmediately below that ledge should also besolid block.


DISCHARGE FANLOCATED IN ATTIC

ROOF VENT FOR SOIL GAS DISCHARGE

RISER PIPES FROMSUMP AND AREAUNDER SLAB

STANDPIPES CAN BE CAPPED FOR FUTURE USE

CONCRETE SLABOVER POLYVAPOR BARRIER

SEALED SUMP PIT COVER

SUCTION TAPCAST IN SLAB

PERIMETER DRAINPIPE AT FOOTING DRAINS TO SUMP

REINFORCED FOOTINGOVER PIPE TRENCH NEAR SUMP

MONOLITHIC CONCRETE OR SOLID PLASTICSUMP WITH PUMP

Figure 2-6: Soil Gas Collection and Discharge Techniques


in new construction. The second phase is thedischarge system, which could be installedlater if necessary.

A foundation with good subsurfacedrainage already has a collection system.The underslab gravel drainage layer can beused to collect soil gas. It should be at least 4inches thick, and of clean aggregate no lessthan 1/2 inch in diameter. Weep holesprovided through the footing or gravel bedextending beyond the foundation wall willhelp assure good air communication betweenthe foundation perimeter soil and theunderside of the slab. The gravel should becovered with a 6-mil polyethylene radon andmoisture retarder, which in turn could becovered with a 2-inch sand bed.

A 3- or 4-inch diameter PVC 12-inchsection of pipe should be inserted verticallyinto the subslab aggregate and capped at thetop. Stack pipes could also be installedhorizontally through below-grade walls tothe area beneath adjoining slabs. A singlestandpipe is adequate for typical house-sizefloors with a clean, coarse gravel layer. Ifnecessary, the standpipe can be uncappedand connected to a vent pipe. The standpipecan also be added by drilling a 4-inch holethrough the finished slab. The standpipeshould be positioned for easy routing to theroof through plumbing chases, interior walls,or closets. Note, however, that it is normallyless costly to complete the vent stack routingthrough the roof during construction than toinstall or complete the vent stack after thebuilding is finished. Connecting the ventpipe initially without the fan provides apassive depressurization system which maybe adequate in some cases and could bedesigned for easy modification to an activesystem if necessary.

A subslab depressurization systemrequires the floor slab to be nearly airtight sothat collection efforts are not short-circuitedby drawing excessive room air down throughthe slab and into the system. Cracks, slabpenetrations, and control joints must besealed. Sump hole covers should bedesigned and installed to be airtight. Floordrains that discharge to the gravel beneaththe slab should be avoided, but when used,should be fitted with a mechanical trapcapable of providing an airtight seal.

Another potential short circuit can occurif the subdrainage system has a gravitydischarge to an underground outfall. Thisdischarge line may need to be provided witha mechanical seal. The subsurface drainage

discharge line, if not run into a sealed sump,should be constructed with a solid-glueddrainpipe that runs to daylight. Thestandpipe should be located on the oppositeside from this drainage discharge.

It is desirable to avoid dependence on acontinuously operating fan. Ideally, apassive depressurization system should beinstalled, radon levels tested and, ifnecessary, the system activated by adding afan. Active systems use quiet, in-line ductfans to draw gas from the soil. The fanshould be located in an accessible section ofthe stack so that any leaks from the positivepressure side of the fan are not in the livingspace. The fan should be oriented to preventaccumulation of condensed water in the fanhousing. The stack should be routed upthrough the building and extend 2 to 4 feetabove the roof. It can also be carried outthrough the band joist and up along theoutside of wall, to a point at or above theeave line. The exhaust should be locatedaway from doors and windows to avoid re-entry of the soil gas into the above-gradespace.

A fan capable of maintaining 0.2 inch ofwater suction under installation conditions isadequate for serving subslab collectionsystems for most houses (Labs 1988). This isoften achieved with a 0.03 hp (25W), 160 cfmcentrifugal fan (maximum capacity) capableof drawing up to 1 inch of water beforestalling. Under field conditions of 0.2 inch ofwater, such a fan operates at about 80 cfm.

It is possible to test the suction of thesubslab system by drilling a small (1/4-inch)hole in an area of the slab remote from thecollector pipe or suction point, andmeasuring the suction through the hole. Asuction of 5 Pascals is considered satisfactory.The hole must be sealed after the test.

Active subslab depressurization doesraise some long-term concerns which at thistime are not fully understood. If the radonbarrier techniques are not fully utilized alongwith the subslab depressurization,considerable indoor air could be discharged,resulting in a larger than expected energypenalty. System durability is of concern,particularly motor-driven components. Thissystem is susceptible to owner interference.


Figure 2-7: System of Key Numbers in Construction Drawingsthat Refer to Notes on Following Pages

RIM JOIST

PROTECTION BOARDOR COATING EXTENDS6 IN. BELOW GRADE 1

GROUND SLOPESAWAY FROM WALLAT 5% (6" IN 10 FT) 2

7-IN. MIN.8-IN. MIN.

2.3 Basement ConstructionDetails

In this section several typical basementwall sections are illustrated and described.Figures 2-8 through 2-10 show configurationswith insulation on the exterior surface ofbasement walls. A typical interior placementconfiguration is shown in Figure 2-11. Figure2-12 illustrates ceiling insulation over anunconditioned basement. A typical woodfoundation wall section is shown in Figure 2-13. Included in this group of details arevariations in construction systems, use ofinsulation under the slab, and approaches toinsulating rim joists. Numbers that occurwithin boxes in each drawing refer to the

notes on pages 31 and 32 that follow thedrawings (see Figure 2-7).

The challenge is to develop integratedsolutions that address all key considerationswithout unnecessarily complicatingconstruction or increasing the cost. There isno one set of perfect solutions; recommendedpractices or details often representcompromises and trade-offs. For example, insome regions termite control may beconsidered more critical than thermalconsiderations, while the reverse is trueelsewhere. No particular approach, such asinterior versus exterior insulation, isconsidered superior in all cases. The purposeof this section is to show and describe avariety of reasonable alternatives. Individualcircumstances will dictate final designchoices.

EXAMPLE OF NOTES CORRESPONDING TOCONSTRUCTION DRAWING:

1. Insulation protection: Exterior insulationmaterials should not be exposed above grade.They should be covered by a protectivematerial — such as exterior grade plastic,fiberglass, galvanized metal or aluminumflashing, a cementitious coating, or a rigidprotection board — extending at least 6 inchesbelow grade.

2. Surface drainage: The ground surfaceshould slope downward at least 5 percent (6inches) over the first 10 feet surrounding thebasement wall to direct surface runoff awayfrom the building. Downspouts and guttersshould be used to collect roof drainage anddirect it away from the foundation walls.


Figure 2-8: Concrete Basement Wall with Exterior Insulation

REINFORCING (OPTIONAL) 12

1/2-IN. ANCHOR BOLTSAT 6 FT. O. C. MAX. 13

CONCRETE FOUNDATION WALL 14

ISOLATION JOINT 15

4-IN. CONCRETE SLABWITH OPTIONAL W. W. MESH 16

VAPOR RETARDER 17

4-IN. GRAVEL DRAINAGE LAYER (OPTIONAL) 18

THROUGH WALL MOISTURE BARRIER / KEYWAY (OPTIONAL) 19

2-IN. DIAMETER WEEP HOLES AT 8 FT. O. C. MAX. (OPTIONAL) 20


4-IN. PERFORATED DRAIN PIPE WITH HOLES FACING DOWN (OPTIONAL) 8

CONCRETE FOOTING 9

LOW PERMEABILITY SOIL(OPTIONAL) 3

DRAINAGE MAT, INSULATING DRAINAGE BOARD, OR GRANULAR BACKFILL (OPTIONAL) 4

RIGID INSULATION 5

DAMPPROOFING OR WATERPROOFING 6

FILTER FABRIC ABOVE GRAVEL (OPTIONAL ON SIDES AND BELOW) 7

COARSE GRAVEL

EXTERIOR SIDING

RIGID INSULATIONSHEATHING

BATT INSULATION

VAPOR RETARDER

GYPSUM BOARD

SUBFLOOR

SEALANT, CAULKINGOR GASKET (OPTIONAL) 10

PRESSURE-TREATEDSILL PLATE 11RIM JOIST




Figure 2-8 illustrates aconcrete foundation wall withexterior insulation. The rigidinsulation also serves assheathing over the 2 x 4 woodframe wall above grade. Thisapproach can be used for rigidinsulation that is 1.5 inchesthick or less.




RIGID INSULATION 5



COARSE GRAVEL

EXTERIOR SIDING

SHEATHING

2 x 6 FRAME WALL OVERHANGS RIM JOIST UP TO 2 IN.




BATT INSULATION

VAPOR RETARDER

GYPSUM BOARD

SUBFLOOR


PRESSURE-TREATEDSILL PLATE 11

RIGID INSULATION 5

RIM JOIST



ISOLATION JOINT 15


2-IN. SAND LAYER(OPTIONAL) 16

VAPOR RETARDER 17






CONCRETE FOOTING 9


Figure 2-9: Concrete Basement Wall with Exterior Insulation

Figure 2-9 illustrates aconcrete foundation wall withexterior insulation. Thisdiffers from Figure 2-8 in thatthe above grade wood framewall is constructed of 2 x 6'swhich overhang the foundationwall. The overhang can be upto 2 inches but additional rigidinsulation can be added thatextends over the entire wallassembly. Another minordifference is that this figureshows a sand layer beneath thefloor slab.




RIGID INSULATION 5



COARSE GRAVEL

EXTERIOR SIDING

SHEATHING

2 x 4 FRAME WALL

1/2-IN. ANCHOR BOLTSAT 6 FT. O. C. MAX. EMBEDDED 7 TO 15 IN. AS REQUIRED BY CODE 31

FILLED BLOCK CORES OR BOND BEAM 33

CONCRETE MASONRY FOUNDATION WALL 22

BATT INSULATION

VAPOR RETARDER

GYPSUM BOARD

SUBFLOOR



FLASHING COVERS TOP OF INSULATION

RIGID INSULATION 5

RIM JOIST



ISOLATION JOINT 15



VAPOR RETARDER 17

RIGID INSULATION (OPTIONAL) 32





CONCRETE FOOTING 9

8-IN. MIN.

Figure 2-10: Masonry Basement Wall with Exterior Insulation

Figure 2-10 illustrates aconcrete masonry foundationwall with exterior insulation.This differs from Figure 2-8and 2-9 in that the rigidfoundation insulation iscovered by a flashing materialat the top. There is no limit tothe thickness of the foundationinsulation. The wood framewall can be either 2 x 4 or 2 x 6construction and does notoverhang the foundation wall.This figure also showsinsulation and a sand layerbeneath the floor slab.


Figure 2-11 illustrates aconcrete foundation wall withinterior insulation. A woodframe wall is constructedinside the foundation wall andbatt insulation is placedbetween the studs. Rigidinsulation can also be placedbetween furring strips on theinterior wall. This figure alsoshows rigid insulation beneaththe floor slab.

RIM JOIST (OPTIONAL CAULKING ABOVE AND BELOW RIM JOIST) 10

PRESSURE-TREATED SILL PLATE 11

GASKET UNDER SILLPLATE 34


LOW PERMEABILITY SOIL (OPTIONAL) 3


DAMPPROOFING OR WATERPROOFING WITHPROTECTION BOARDAS REQUIRED 6



COARSE GRAVEL

EXTERIOR SIDING

SHEATHING

2 x 6 FRAME WALL OVERHANGS RIM JOIST UP TO 2 IN.


INSULATION IN FRAME WALL 24

VAPOR RETARDER

FINISH MATERIAL

BATT INSULATION

VAPOR RETARDER

GYPSUM BOARD

SUBFLOOR

RIGID INSULATION INJOINT (OPTIONAL) 15

PRES.-TREATED PLATE

4-IN. CONCRETE SLABWITH W. W. MESH 16

VAPOR RETARDER 17

RIGID INSULATION (OPTIONAL) 32






CONCRETE FOOTING 9

8-IN. MIN. 7-IN. MIN.


BATT INSULATION

RIGID INSULATION CAULKED AT ALL EDGES FORMS AVAPOR RETARDER (OPTIONAL) 23

Figure 2-11: Concrete Basement Wall with Interior Insulation




DAMPPROOFING OR WATERPROOFING WITHPROTECTION BOARDAS REQUIRED 6


COARSE GRAVEL

EXTERIOR SIDING

SHEATHING

INSULATION BETWEEN FLOOR JOISTS WITH VAPOR RETARDER ON TOP OF INSULATION 25




BATT INSULATION

VAPOR RETARDER

GYPSUM BOARD

SUBFLOOR

RIM JOIST (OPTIONALCAULKING ABOVE AND BELOW RIM JOIST) 10

PRESSURE-TREATEDSILL PLATE WITH GASKET 11


ISOLATION JOINT 15


VAPOR RETARDER 17






CONCRETE FOOTING 9

8-IN. MIN.

7-IN. MIN.

Figure 2-12: Concrete Basement Wall with Ceiling Insulation

Figure 2-12 illustrates abasement with insulationplaced in the ceiling betweenthe floor joists. This approachis appropriate for anunconditioned basement. Itshould be used with caution incolder climates and any ductsand pipes in the basementshould be insulated.


Figure 2-13 illustrates apressure-preservative-treatedwood foundation wall.Insulation is placed betweenthe studs similar to aconventional wood frame wall.

PRESSURE-TREATED FOOTING PLATE

GRAVEL FOOTING PAD BENEATH FOOTING PLATE 27

VAPOR RETARDER 17

4-IN. GRAVEL DRAINAGE LAYER DRAINS TO SUMP 30

EXTERIOR SIDING

SHEATHING

BATT INSULATION IN WOOD FRAME WALL

CEILING FINISH MATERIAL

PRESSURE-TREATED WOOD FRAME WALL 28

INSULATION 29

VAPOR RETARDER

INTERIOR FINISH MATERIAL


VAPOR RETARDER

SUBFLOOR

RIM JOIST (OPTIONAL CAULKING ABOVE OR BELOW RIM JOIST) 10

FIELD-APPLIED TOP PLATE

WALL SYSTEM TOP PLATE 11



W1/2-WMIN.

1/2-WMIN.

3/4-WMIN.

BATT INSULATION

RIGID INSULATION CAULKED AT ALL EDGES FORMS VAPOR RETARDER (OPTIONAL) 23

2-IN. AIR SPACE 35

4-IN. CONCRETE SLAB WITH OPTIONAL W. W. MESH 16 36


COARSE GRAVEL BACKFILL ON LOWER HALF OF WALL 26

PRESSURE-TREATED PLYWOOD

6-MIL POLY WATER SHEDDING MEMBRANE 6

Figure 2-13: Pressure-Preservative-Treated Wood Basement Wall


failure. Drainpipes should slope 1 inch in 20 feet andlead to an outfall or sump. A vertical clean-out pipewith an above-grade capped end is recommended toflush out the system. The top of the pipe should bebelow the level of the underside of the basement floorslab. The pipe should be surrounded by at least 6inches of gravel on the sides and 4 inches of gravelabove and below the pipe. Surface or roof drainagesystems should never be connected to thesubsurface drainage system. (Optional)

9. Concrete footing: All concrete footings must bedesigned with adequate size to distribute the load tothe soil and be placed beneath the maximum frostpenetration depth or insulated to prevent frostpenetration. Concrete used in spread footings shouldhave a minimum compressive strength of 2500 psi.

10. Caulking: Caulking at the following interfacesminimizes air leakage: foundation wall/sill plate, sillplate/rim joist, rim joist/subfloor, subfloor/above-gradewall plate. An alternative is to cover these points onthe exterior with an air barrier material. (Optional)

11. Sill plate: The sill plate should be at least 8inches above grade and should be pressure-preservative treated to resist decay.

12. Crack control reinforcing in walls: Even whenno structural reinforcing is required, reinforcing isdesirable to minimize shrinkage cracking. Two No. 4bars running continuously 2 inches below the top ofthe wall and above/below window openings arerecommended. (Optional)

13. Anchor bolts in concrete walls: Anchor boltsshould be embedded in the top of concretefoundation walls to resist uplift. Most codes requirebolts of 1/2-inch minimum diameter to be embeddedat least 7 inches into the wall. Generally, anchorbolts can be placed at a maximum spacing of 6 feetand no further than 1 foot from any corner.

14. Cast-in-place concrete wall: Concrete used inthe wall should have a minimum compressivestrength of 2500 psi with a 4- to 6-inch slump. Noadditional water should be added at the job site.Generally, where there are stable soils in areas of lowseismic activity, no reinforcing is required in an 8-inch-thick basement wall with up to 7 feet of fill.

15. Isolation joint: An isolation joint should beprovided at the slab edge to permit vertical movementwithout cracking. Where radon is a concern, a liquidsealant should be poured into the joint over a foambacking rod. Rigid insulation placed in the jointprevents a thermal bridge when there is insulationbeneath the slab.

16. Concrete slab: A minimum slab thickness of 4inches is recommended using concrete with aminimum compressive strength of 2500 psi. Weldedwire fabric placed 2 inches below the slab surface isrecommended to control shrinkage cracks in areas ofhigh radon and termite hazard. Generally, concreteslabs should not rest on footings or ledges offoundation walls if possible to avoid cracking due tosettlement. If a slab is poured directly over animpermeable vapor retarder or insulation board, aconcrete mixture with a low water/cement ratio isrecommended. An alternative technique is to pourthe slab on a layer of sand or drainage board materialabove the vapor retarder to minimize cracking.

NOTES FOR ALL DETAILEDBASEMENT DRAWINGS(FIGURES 2-8 THROUGH 2-13)

1. Insulation protection: Exterior insulationmaterials should not be exposed above grade. Theyshould be covered by a protective material — such asexterior grade plastic, fiberglass, galvanized metal oraluminum flashing, a cementitious coating, or a rigidprotection board — extending at least 6 inches belowgrade.

2. Surface drainage: The ground surface shouldslope downward at least 5 percent (6 inches) over thefirst 10 feet surrounding the basement wall to directsurface runoff away from the building. Downspoutsand gutters should be used to collect roof drainageand direct it away from the foundation walls.

3. Backfill cover: Backfill around the foundationshould be covered with a low permeability soil, or amembrane beneath the top layer of soil, to divertsurface runoff away from the foundation. (Optional)

4. Backfill or drainage materials: Porous backfillsand or gravel should be used against the walls topromote drainage. Backfill should be compacted sothat settlement is minimized. In place of porousbackfill, a drainage mat material or insulatingdrainage board can be placed against the foundationwall. The drainage mat should extend down to adrainpipe at the footing level. (Optional)

5. Exterior insulation materials: Acceptablematerials for exterior insulation are: (1) extrudedpolystyrene boards (XEPS) under any condition, (2)molded expanded polystyrene boards (MEPS) forvertical applications when porous backfill andadequate drainage are provided, and (3) fiberglass orMEPS drainage boards when an adequate drainagesystem is provided at the footing.

6. Dampproofing/waterproofing: A dampproofcoating covered by a 4-mil layer of polyethylene isrecommended to reduce vapor transmission from thesoil through the basement wall. Parging isrecommended on the exterior surface of masonrywalls before dampproofing. Waterproofing isrecommended on sites with anticipated waterproblems or poor drainage. Waterproofing should beplaced on the exterior directly over the concrete,masonry, or wood substrate. Exterior insulationshould be placed over the waterproofing.Waterproofing should extend down to the level of thedrainage system at the footing.

7. Filter fabric: A filter fabric over the gravel bed anddrainpipe is recommended to prevent clogging of thedrainage area with fine soil particles. Wrapping thefilter fabric around the entire gravel bed is an optionaltechnique for better protection against clogging.

8. Drainage system: Where drainage problems arenot anticipated, a gravel bed placed along the footingwill provide adequate drainage. Where conditionswarrant, a 4-inch-diameter perforated drainpipeshould be installed in the gravel. Perforateddrainpipes should be placed with holes facingdownward alongside the footing on either the outsideor inside. Outside placement is preferred fordrainage but inside placement is less susceptible to


17. Vapor retarder: A 6-mil polyethylene vaporretarder should be placed beneath the slab to reducemoisture transmission and radon infiltration into thebasement.

18. Gravel layer under slab: A 4-inch gravel layershould be placed under the concrete floor slab fordrainage where local conditions suggest basementleakage may be a problem. (Optional)

19. Moisture barrier and wall/footing connection:The concrete wall should be anchored to the footingin one of three ways: (1) sufficient roughening of thetop of the footing to prevent sliding, (2) by use of akeyway, or (3) by use of reinforcing dowels. Athrough-wall moisture barrier is recommendedbetween a concrete wall and footing to preventcapillary draw. (Optional)

20. Weep holes: Two-inch-diameter weep holesthrough the footing 4 to 8 feet apart may be used toconnect the underfloor drainage layer to the drainagesystem outside the footing. (Optional)

21. Crack control reinforcing in footing:Reinforcing bars placed 2 inches below the top of thefooting running parallel to the wall are recommendedwhere differential settlement is a potential problem.(Optional unless required)

22. Masonry wall: Generally where there are stablesoils in areas of low seismic activity, no reinforcing isrequired in a 12-inch-thick masonry wall with up to 6feet of fill. When reinforcing is required, it must begrouted into block cores. Vertical bars should bespaced no more than 48 inches apart or 6 times thewall thickness, whichever is less.

23. Insulation inside rim joist: Insulation can beplaced on the inside of the rim joist but with greaterrisk of condensation problems and less access towood joists and sills for inspection from the interior.Low permeability rigid insulation (such as extrudedpolystyrene) should be used, or a vapor retardershould be placed on the inside of the insulation andsealed to all surrounding surfaces.

24. Interior insulation materials: For interiorplacement, virtually any batt, blown, or foaminsulation is acceptable. Most products require athermal barrier for fire protection. The use of foaminsulation does not require a frame wall—only furringstrips are required.

25. Ceiling insulation: Insulation placement in thebasement ceiling is an effective alternative where anunconditioned basement is acceptable and ducts areadequately insulated. With fiberglass insulationplaced between the wood joists, the vapor retardershould be on the warm side of the insulation facingupwards.

26. Gravel backfill for wood foundation: Coarsegravel backfill should be placed against the lower halfof the walls to promote drainage. Backfill should belightly compacted so that settlement is minimized.

27. Gravel bed beneath wood foundation wall: Acompacted gravel bed may serve as the footingunder a wood foundation wall. Beneath the wall thegravel layer should be at least 6 inches thick (orthree-quarters of the bottom wall plate width,whichever is greater), and the bed should extend out

from the footing at least 6 inches on each side (orone-half of the bottom wall plate width).

28. Wood foundation walls: Wood foundation wallsmust be designed to resist lateral and vertical loadsand must be constructed of lumber and plywood thatis properly treated to resist decay. Wall constructionand material specifications are found in the NationalForest Products Association design manual (NFPA1987). Local codes should be consulted for specificrequirements.

29. Insulation in wood foundation walls: Batt,blown, or foam insulations are placed within the studcavities of a wood foundation system and a vaporretarder is placed on the warm side of the wall.

30. Gravel beneath floor of wood foundationsystem: A 4-inch layer of gravel should be beneaththe floor of a wood foundation system with a sumparea located in the middle of the basement. Thesump area should be at least 24 inches deep andeither 16 inches in diameter or 16 inches square, andcan be formed with clay tile flue liner or concretepipe. The sump must drain to daylight or be providedwith a pump (National Forest Products Association,1987).

31. Anchor bolts in masonry walls: Anchor boltsshould be embedded in the top of masonryfoundation walls. Most codes require bolts of 1/2-inch minimum diameter embedded at least 7 inchesinto the wall. In some locations, codes require boltsto be embedded 15 inches in masonry walls to resistuplift. To provide adequate anchorage in a masonrywall, bolts either must be embedded in a bond beamor the appropriate cores of the upper course of blockmust be filled with mortar. Generally, anchor boltscan be placed at a maximum spacing of 6 feet and nofurther than 1 foot from any corner.

32. Insulation under the slab: Acceptable materialsfor underslab insulation are: (1) extruded polystyreneboards (XEPS) under any condition, (2) moldedexpanded polystyrene boards (MEPS) when thecompressive strength is sufficient and adequatedrainage is provided, and (3) insulating drainageboards with sufficient compressive strength.

33. Bond beam on masonry wall: When requiredby code or structural consideration, a bond beamprovides additional lateral strength in a masonry wall.Using a bond beam or filling the cores of the uppercourses of block also are recommended as radonand termite prevention techniques. (Optional)

34. Gasket: To minimize air leakage, use acompressible foam plastic sill sealer or equivalent.

35. Air space: A 2-inch air space should be providedbetween the end of the insulation and the bottomplate.

36. Pressure-preservative-treated wood floor:Instead of a concrete floor slab, pressure-preservative-treated wood floors are sometimes usedin conjunction with wood foundations. These floorsare required to resist the lateral loads being imposedat the bottom of the foundation wall as well as toresist excessive deflection from the vertical floor load.


2.4 Checklist for Design and Construction of Basements

This checklist serves as a chapter summary, helps review the completeness ofconstruction drawings and specifications, and provides general guidance on projectmanagement. The checklist could be used many ways. For example, use one set of blanksduring design and the second set during construction inspection. Note that not all measuresare necessary under all conditions. Use different symbols to distinguish items that have beensatisfied (+) from those that have been checked but do not apply (x). Leave unfinished itemsunchecked.

SITEWORK

____ ____ Locate building at the highest point if the site is wet____ ____ Define “finish subgrade” (grading contractor), “base grade” (construction

contractor), “rough grade” level before topsoil is respread, “finishgrade” (landscape contractor)

____ ____ Establish elevations of finish grades, drainage swales, catch basins,foundation drain outfalls, bulkheads, curbs, driveways, propertycorners, changes in boundaries

____ ____ Establish grading tolerances____ ____ Provide intercepting drains upgrade of foundation if needed____ ____ Locate dry wells and recharge pits below foundation level____ ____ Establish precautions for stabilizing excavation____ ____ Establish limits of excavation and determine trees, roots, buried cables,

pipes, sewers, etc., to be protected from damage____ ____ Confirm elevation of water table____ ____ Determine type and dimensions of drainage systems____ ____ Discharge roof drainage away from foundation____ ____ Remove stumps and grubbing debris from site____ ____ Provide frost heave protection for winter construction____ ____ Call for test hole (full depth hole in proposed foundation location)____ ____ Locate stakes and benchmarks____ ____ Strip and stock pile topsoil____ ____ Define spoil site

FOOTINGS

____ ____ Position bottom of footing at least 6 inches below frost depth aroundperimeter (frost wall at garage, slabs supporting roofs, other elementsattached to structure). Make sure footing is deeper under basementwalkouts

____ ____ Confirm adequacy of footing sizes____ ____ Do not fill the overexcavated footing trench____ ____ Install longitudinal reinforcing (two No. 4 or No. 5 bars 2 inches from top)____ ____ Reinforce footing at spans over utility trenches____ ____ Do not bear footings partially on rock (sand fill)____ ____ Do not pour footings on frozen ground____ ____ Indicate minimum concrete compressive strength after 28 days____ ____ Call out elevations of top of footings and dimension elevation changes in

plan____ ____ Use keyway or steel dowels to anchor walls____ ____ Dimension stepped footings according to local codes and good practice

(conform to masonry dimensions if applicable)____ ____ Provide weep holes (minimum 2-inch diameter at 4 feet to 8 feet on center)____ ____ Provide through-joint flashing as a capillary break


BASEMENT CHECKLIST (PAGE 2 OF 5)

CAST-IN-PLACE CONCRETE WALLS

____ ____ Determine minimum compressive strength after 28 days____ ____ Determine maximum water/cement ratio. (Note: add no water at site)____ ____ Determine allowable slump____ ____ Determine acceptable and unacceptable admixtures____ ____ Determine form-release agents acceptable to WPM manufacturer____ ____ Establish curing requirements (special hot, cold, dry conditions)____ ____ Establish surface finish requirements and preparation for WPM (plug all

form tie holes)____ ____ For shrinkage control: use horizontal reinforcing at top of wall and/or

control joints____ ____ Design width of wall to resist height of fill, seismic loads, and loads

transmitted through soil from adjacent foundations____ ____ Use two-way reinforcing (horizontal and vertical) for strength,

watertightness, termite and radon resistance____ ____ Establish anchor bolt depth and spacing requirements, and install

accordingly____ ____ Provide cast-in-place anchors for joist ends____ ____ Establish beam pocket elevations, dimensions, details____ ____ Determine top of wall elevations and changes in wall height____ ____ Determine brick shelf widths and elevations

CONCRETE MASONRY WALLS

____ ____ Specify mortar mixes and strengths____ ____ Size walls to resist height of fill, seismic loads, loads transmitted through

soil from adjacent foundations____ ____ Grout top courses of block to receive anchor bolts____ ____ Indicate special details for proprietary masonry systems____ ____ Ensure that the surface quality is suitable to WPM____ ____ Prepare exterior surface for application of dampproofing or WPM (special

preparation consisting of cement parging, priming)____ ____ For crack control, use bond beam or horizontal joint reinforcing

FLOOR SLAB

____ ____ Determine minimum compressive strength after 28 days____ ____ Determine maximum water/cement ratio. (Note: add no water at site)____ ____ Determine allowable slump____ ____ Determine acceptable and unacceptable admixtures____ ____ Establish curing requirements (special hot, cold, dry conditions)____ ____ Determine surface finish____ ____ Provide shrinkage control: WWF reinforcement or control joints____ ____ Provide isolation joints at wall perimeter and column pads____ ____ Provide vapor retarder under slab____ ____ Provide sand layer over vapor retarder or insulation board____ ____ Compact fill under slab



BACKFILLING AND COMPACTION

____ ____ Establish minimum concrete strength or curing prior to backfilling____ ____ Use high early strength concrete if necessary____ ____ Install temporary wall support during backfilling____ ____ Establish condition of fill material (if site material stays in clump after

soaking and squeezing in hand, do not use as backfill)____ ____ Determine proper compaction____ ____ Cap backfill with an impermeable cover

SUBDRAINAGE

General considerations. Footing drains (1) draw down the ground water level; (2)prevent ponds of rainwater and snow melt in the backfill. The underslab drainage layer (1)conveys rising groundwater laterally to collecting drain lines; (2) acts as a distribution andtemporary storage pad for water that drains through the backfill and would otherwise formponds at the bottom.

____ ____ Use gravel pad and footing weep holes____ ____ Position high end of footing drains below underside of floor slab (Note:

outside footing placement is preferred for drainage; inside placementis less susceptible to failure)

____ ____ Ensure footing drain is pitched____ ____ Lay footing drain on compacted bedding (minimum 4 inches thick)____ ____ Set unperforated leaders to drain to outfall (hand backfill first 8 inches to

avoid damaging pipe)____ ____ Ensure that transitions are smooth between pipes of different slopes____ ____ Separate surface, roof, and foundation drain systems____ ____ Call out gravel or crushed stone envelope around drainpipe and wrap

with a synthetic filter fabric____ ____ Locate clean-outs for flushing the system____ ____ Install porous backfill or wall-mounted drainage product____ ____ Provide minimum 4-inch-thick gravel or stone layer under slab____ ____ If large flow of water is anticipated, use curtain drain to intercept

MOISTUREPROOFING

General considerations. Waterproofing is usually recommended for all below-gradeliving and work spaces. Dampproofing provides a capillary break and serves as a vaporretarder. Waterproof membranes (WPM) dampproof, but dampproofing does notwaterproof.

____ ____ Either dampproof or waterproof walls____ ____ Place a polyethylene vapor retarder under floor slabs (optional sand layer

between polyethylene and slab)____ ____ Place a continuous WPM under slab for basements below groundwater

(special detailing and reinforcement required for support)____ ____ Install control and expansion joints according to recommendations of

WPM manufacturer____ ____ Provide protection board for WPM



THERMAL AND VAPOR CONTROLS

General considerations. Exterior insulation maintains the wall close to indoortemperature. This can eliminate the need for vapor retarders on the interior and keepsrubber and asphalt-based moistureproofing warm and pliable. Interior and integralinsulations require a vapor retarder at the inside surface. Difficulty of vapor sealing at therim joist generally favors exterior insulation.

____ ____ Verify that wall insulation R-value and depth meet local codes and/orrecommendations from this handbook

____ ____ Insulate ceiling in unconditioned basements____ ____ If used, specify exterior insulation product suitable for in-ground use____ ____ Install protective coating for exterior insulation____ ____ Install polyethylene slip sheet between soil and wall (nondrainage)

insulation____ ____ Install vapor retarder at inside face of internally and integrally insulated

walls____ ____ Place a fire-protective cover over combustible insulations____ ____ Install infiltration sealing gasket under sill plate____ ____ Seal air leakage penetrations through rim joists____ ____ Install an air barrier outside rim joist

DECAY AND TERMITE CONTROL

General considerations. Strategy: (1) Isolate wood members from soil by an air space orimpermeable barrier; (2) expose critical areas for inspection. Pressure-treated lumber is lesssusceptible to attack, but is no substitute for proper detailing. Termite shields are not reliablebarriers unless installed correctly.

____ ____ Pressure-treat wood posts, sill plates, rim joists, wood members in contactwith foundation piers, walls, floors, etc.

____ ____ Pressure-treat all outdoor weather-exposed wood members____ ____ Install dampproof membrane under sill plate and beams in pockets

(flashing or sill seal gasket)____ ____ Leave minimum 1/2-inch air space around beams in beam pockets____ ____ Expose sill plates and rim joists for inspection____ ____ Elevate sill plate minimum 8 inches above exterior grade____ ____ Elevate wood posts and framing supporting porches, stairs, decks, etc.,

above grade (6-inch minimum) on concrete piers____ ____ Elevate wood siding, door sills, other finish wood members at least 6

inches above grade (rain splash protection)____ ____ Separate raised porches and decks from the building by 2-inch horizontal

clearance for drainage and termite inspection (or provide properflashing)

____ ____ Pitch porches, decks, patios for drainage (minimum 1/4 in/ft)____ ____ Treat soil with termiticide, especially with insulated foundations____ ____ Reinforce slab-on-grade____ ____ Remove all grade stakes, spreader sticks, and wood embedded in concrete

during pour____ ____ Do not disturb treated soil prior to pouring concrete slab____ ____ Reinforce cast-in-place concrete walls (with No. 5 bars) along the top and

bottom to resist settlement cracking



RADON CONTROL

General considerations. The potential for radon hazard is present in all buildings.Check state and local health agencies for need of protection. Strategies include: (1) barriers;(2) air management; and (3) provisions to simplify retrofit. Since radon is a gas, its rate ofentry through the foundation depends on suction due to stack effect and superstructure airleakage.

____ ____ Separate outdoor intakes for combustion devices____ ____ Install air barrier wrap around superstructure____ ____ Seal around flues, chases, vent stacks, attic stairs____ ____ Install polyethylene vapor retarder as floor underlayment between first

floor and unconditioned basement____ ____ Reinforce cast-in-place concrete walls (with No. 5 bars) along the top and

bottom to resist settlement cracking____ ____ For crack control in masonry walls, use bond beam or horizontal joint

reinforcing____ ____ Seal top of hollow masonry walls with solid block, bond beam, or cap

block____ ____ Parge exterior face of masonry walls____ ____ Install continuous moistureproofing on the outside of masonry walls____ ____ Reinforce slab-on-grade____ ____ Remove all grade stakes, spreader sticks, and wood embedded in concrete

during pour____ ____ Form perimeter wall/floor joint trough for pour-in sealant____ ____ Place vapor retarder under slab (with optional sand layer)____ ____ Caulk joints around pipes and conduits____ ____ Install sump pit with airtight cover____ ____ Vent sump pit to outside____ ____ Do not use floor drains, unless mechanical trap valves are used____ ____ Lay minimum 4-inch-thick layer of coarse, clean gravel under slab____ ____ Cast 4-inch-diameter PVC tubing standpipes (capped) into slab

PLANS, CONTRACTS, AND BUILDING PERMITS

____ ____ Complete plans and specifications____ ____ Complete bid package____ ____ Establish contractual arrangements (describe principals, describe the work

by referencing the blueprints and specs, state the start/completiondates, price, payment schedule, handling of change orders, handling ofdisputes, excavation allowance, and procedure for firing)

____ ____ Acquire building permits

SITE INSPECTIONS DURING CONSTRUCTION

____ ____ After excavation and before concrete is poured for the footings____ ____ After the footings have been poured before foundation wall construction____ ____ After foundation construction and dampproofing before rough framing____ ____ After rough framing____ ____ After rough plumbing and electrical____ ____ After insulation installation before drywall and backfilling in case of

exterior insulation____ ____ Final

Chapter 3—Crawl Space Construction

This chapter summarizes suggestedpractices related to crawl spaces. Section 3.1presents various insulation configurationsalong with recommended optimal levels ofinsulation for vented and unvented crawlspaces.

Section 3.2 summarizes crawl spacedesign and construction practices in thefollowing areas: structural design, location ofinsulation, drainage and waterproofing,termite and decay control, and radon control.Section 3.3 includes a series of alternativeconstruction details with accompanyingnotes indicating specific practices. Section 3.4is a checklist to be used during the design,construction, and site inspection of a crawlspace.

3.1 Crawl Space InsulationPlacement and Thickness

To provide energy use information forbuildings with crawl space foundations,heating and cooling loads were simulated fora variety of insulation placements andthicknesses in representative U.S. climates(Labs et al. 1988). Two types of crawl spaceswere analyzed for energy purposes — ventedand unvented. Generally most majorbuilding codes require vents near eachcorner. These vents may have operablelouvers. The vented crawl space is assumedto have venting area openings of 1 squarefoot per 1500 square feet of floor area. Thetemperature of the vented crawl space variesbetween the interior house temperature andthe exterior temperature. The unventedcrawl space is assumed to have vents fully

Figure 3-1: Concrete Crawl Space Wallwith Exterior Insulation

CHAPTER 3

Crawl Space Construction


closed, leaving only gaps in construction thatcould allow infiltration. Unvented crawlspaces insulated at the perimeter are similarto unheated basements, with temperaturesthat fluctuate between 50OF and 70OF most ofthe year, depending on climate andinsulation placement.

Crawl spaces can vary in height andrelationship to exterior grade. It is assumedin the analysis that follows that crawl spacewalls are 2 feet high with only the upper 8inches of the foundation wall exposed abovegrade on the exterior side.

Insulation Configurations and Costs

Table 3-1 includes illustrations anddescriptions of a variety of crawl spaceinsulation configurations. Two basicconstruction systems are shown for unventedcrawl spaces — a concrete (or masonry)foundation wall and a pressure-preservative-treated wood foundation wall. For ventedcrawl spaces, concrete (or masonry) walls areshown.

In a vented crawl space, insulation isplaced between the floor joists in the crawlspace ceiling. In an unvented crawl space,the two most common approaches toinsulating concrete/masonry walls are(1) covering the entire wall on the exterior,and (2) covering the entire wall on theinterior. In addition to these conventionalapproaches, insulation can be placed on theinterior wall and horizontally on theperimeter of the crawl space floor (extendingeither 2 or 4 feet into the space). Withpressure-preservative-treated woodconstruction, batt insulation is placed in thecavities between the wood studs.


While increasing the amount of crawlspace insulation produces greater energysavings, the cost of installation must becompared to these savings. Such acomparison can be done in several ways;however, a life cycle cost analysis (presentedin worksheet form in Chapter 5) isrecommended since it takes into account anumber of economic variables includinginstallation costs, mortgage rates, HVACefficiencies, and fuel escalation rates. Inorder to identify the most economicalamount of insulation for the crawl spaceconfigurations shown in Table 3-1, the casewith the lowest 30-year life cycle cost was

determined for five U.S. cities at threedifferent fuel cost levels. See the BuildingFoundation Design Handbook (Labs et al. 1988)to find recommendations for a greaternumber of cities and for a detailedexplanation of the methodology. Theeconomic methodology used to determinethe insulation levels in Table 3-1 is consistentwith ASHRAE standard 90.2P. The simplepayback averages 13 years for all U.S. climatezones, and never exceeds 18 years for any ofthe recommended levels.

Economically optimal configurations areshown by the darkened circles in Table 3-1 inthe following categories: (1) unvented crawlspaces with concrete/masonry walls andexterior insulation, (2) unvented crawl spaceswith concrete/masonry walls and interiorinsulation, (3) unvented crawl spaces withwood walls, and (4) vented crawl spaces withconcrete walls. Configurations arerecommended for a range of climates andfuel prices in each of these categories, but thedifferent categories of cases are not directlycompared with each other. In other words,there is an optimal amount of exteriorinsulation recommended for a given climateand fuel price, and there is a differentoptimal amount of insulation for interiorinsulation. Where there is no darkened circlein a particular category, insulation is noteconomically justified under the assumptionsused.

For unvented crawl spaces withconcrete/masonry walls, exterior insulationranging from R-5 to R-10 is justified at all fuelprice levels (shown in Table 3-2) in all climatezones except the warmest one. Similar levelsof interior insulation are recommended.However in colder climates, placinginsulation horizontally on the crawl spacefloor in addition to the wall is frequently theoptimal configuration. If the crawl spacewall is higher than 2 feet, as it often must beto reach frost depth in a colder climate, it isadvisable to extend the vertical insulation tothe footing. Although simulation results forcrawl spaces with higher walls and deeperfootings are not shown here, the need forinsulation placed deeper than 2 feet in coldclimates is obvious and is reflected by theeconomic benefits of placing insulation onthe floor of a shallower crawl space.

For unvented crawl spaces withpressure-preservative-treated wood walls,insulation ranging from R-11 to R-19 isjustified in moderate and colder climates. Invented crawl spaces, ceiling insulation


Table 3-1: Insulation Recommendations for Crawl Spaces

CONFIGURATION DESCRIPTION

EXTERIOR VERTICAL

INTERIOR VERTICAL

WITHIN WOOD WALL

A: Unvented Crawl Space - Concrete or Masonry Foundation Walls with Exterior Insulation

C: Unvented Crawl Space - Pressure-Treated Wood Foundation Walls

NO INSULATION

2 FT: R-5 RIGID

2 FT: R-10 RIGID

NO INSULATION

2 FT: R-5 RIGID

2 FT: R-10 RIGID

NO INSULATION

2 FT: R-11 BATT

2 FT: R-19 BATT

B: Unvented Crawl Space - Concrete or Masonry Foundation Walls with Interior Insulation

CEILING

D: Vented Crawl Space - Concrete or Masonry Foundation Walls with Ceiling Insulation

NO INSULATION

R-11 BATT

R-19 BATT

R-30 BATT

INTERIOR VERTICALAND HORIZONTAL 2 FT/2 FT: R-5 RIGID

2 FT/4 FT: R-5 RIGID



0-2000 HDD(LOS ANG)



6-8000 HDD(CHICAGO)

8-10000 HDD(MPLS)





wall, the economic benefit of interior versusexterior insulation may be offset by otherpractical, performance, and aestheticconsiderations discussed elsewhere in thisbook. Although ceiling insulation in a ventedcrawl space appears more cost-effective thanwall insulation in an unvented space, avented crawl space may be undesirable incolder climates since pipes and ducts may beexposed to freezing temperatures. In allcases the choice of foundation type andinsulation system must be based on manyfactors in addition to energy cost-effectiveness.

Assumptions


The total installed costs for all insulationsystems considered in this analysis areshown in Table 5-2 in chapter 5. Installationcosts used in this analysis are based onaverage U.S. costs in 1987. For the exteriorcases, costs include labor and materials forextruded polystyrene insulation and therequired protective covering and flashingabove grade. For the interior cases, costsinclude labor and materials for expandedpolystyrene. All costs include a 30 percentbuilder markup and a 30 percentsubcontractor markup for overhead andprofit.

With pressure-preservative-treated woodconstruction, batt insulation is placed in the

ranging from R-11 to R-30 is recommended inall climates at all fuel price levels.

Comparison of Insulation Systems

Insulating the ceiling of a vented crawlspace is generally more cost-effective thaninsulating the walls of an unvented crawlspace to an equivalent level. This is becauseplacing mineral wool batt insulation into theexisting spaces between floor joistsrepresents a much smaller incremental costthan placing rigid insulation on the walls.Thus higher levels of insulation arerecommended in the floor above a ventedcrawl space than for the walls of an unventedspace.

When exterior and interior insulation arecompared for an unvented crawl space withconcrete/masonry walls, thermal results arevery similar for equivalent amounts ofinsulation. Since it is assumed that exteriorinsulation costs more to install, however,interior placement is always economicallyoptimal in comparison. This increased costfor an exterior insulation is attributed to theneed for protective covering and a higherquality rigid insulation that can withstandexposure to water and soil pressure.

Generally, insulating pressure-preservative-treated wood walls is more cost-effective than insulating concrete/masonrywalls to an equivalent level. This is becausethe cavity exists between studs in a woodwall system and the incremental cost ofinstalling batt insulation in these cavities isrelatively low. Thus, a higher R-value iseconomically justified for wood wall systems.

In spite of the apparent energy efficiencyof wood versus concrete/masonry basementwalls, this is only one of many cost andperformance issues to be considered.Likewise, on a concrete/masonry foundation

Table 3-2: Fuel Price Levels Used to Develop Recommended Insulation Levels in Table 3-1


NATURAL GAS

FUEL OIL

PROPANE

HEATING

COOLING ELECTRICITY

.374 / THERM

.527 / GALLON

.344 / GALLON

.051 / KWH

.561 / THERM

.791 / GALLON

.516 / GALLON

.076 / KWH

.842 / THERM

1.187 / GALLON

.775 / GALLON

.114 / KWH


cavities between the wood studs. Costs forwood foundations reflect the additional costof installing insulation with an ASTM E-84flame spread index of 25 or less in a woodfoundation wall.

If the general assumptions used in thisanalysis are satisfactory for the specificproject, the reader can determine theapproximate recommended insulation levelfor a location by finding the heating degreedays from Table 5-1 in chapter 5 andselecting the appropriate climate zone andfuel price level shown in Table 3-1. If not,project-specific optimal insulation levels canbe determined using actual estimatedconstruction costs with the worksheetprovided in chapter 5. The worksheetenables the user to select economic criteriaother than allowing maximum simplepaybacks of 18 years. In addition, the usercan incorporate local energy prices, actualinsulation costs, HVAC efficiencies, mortgageconditions, and fuel escalation rates. Cost-effectiveness can vary considerably,depending on the construction details andcost assumptions.


VENTED VERSUS UNVENTEDCRAWL SPACES

The principal perceived advantage of avented crawl space over an unvented one isthat venting can minimize radon andmoisture-related decay hazards by dilutingthe crawl space air. Venting can complementother moisture and radon control measuressuch as ground cover and proper drainage.However, although increased air flow in thecrawl space may offer some dilution potentialfor ground source moisture and radon, it willnot necessarily solve a serious problem. Theprincipal disadvantages of a vented crawlspace over an unvented one are that (1) pipesand ducts must be insulated against heat lossand freezing, (2) a larger area usually must beinsulated, which may increase the cost, and(3) in some climates warm humid aircirculated into the cool crawl space canactually cause excessive moisture levels inwood. Vented crawl spaces are oftenprovided with operable vents that can beclosed to reduce winter heat losses, but also

potentially increase radon infiltration.Although not their original purpose, thevents can also be closed in summer to keepout moist exterior air that can have a dewpoint above the crawl space temperature.

It is not necessary to vent a crawl spacefor moisture control if it is open to anadjacent basement, and venting is clearlyincompatible with crawl spaces used as heatdistribution plenums. In fact, there areseveral advantages to designing crawl spacesas semi-heated zones. Duct and pipeinsulation can be reduced, and thefoundation is insulated at the crawl spaceperimeter instead of its ceiling. This usuallyrequires less insulation, simplifies installationdifficulties in some cases, and can be detailedto minimize condensation hazards.Nevertheless, venting of crawl spaces may bedesirable in areas of high radon hazard.However, venting should not be considered areliable radon mitigation strategy.Pressurizing the crawl space is onepotentially effective method of minimizingsoil gas uptake, but the crawl space walls andceiling must be tightly constructed for thisapproach to be effective.

Although unvented crawl spaces havebeen recommended, “except under severemoisture conditions,” by the University ofIllinois’s Small Homes Council (Jones 1980),moisture problems in crawl spaces arecommon enough that many agencies areunwilling to endorse closing the vents year-round. Soil type and the groundwater levelare key factors influencing moistureconditions. It should be recognized that acrawl space can be designed as a shortbasement (with slurry slab floor), and, havinga higher floor level, is subject to less moisturehazard in most cases. Viewed in this way,the main distinction between unvented crawlspaces and basements is in the owner’saccessibility and likelihood of noticingmoisture problems.

STRUCTURAL DESIGN

The major structural components of acrawl space are the wall and the footing (seeFigure 3-2). Crawl space walls are typicallyconstructed of cast-in-place concrete, concretemasonry units, or pressure-treated wood.Crawl space walls must resist any lateralloads from the soil and vertical loads fromthe structure above. The lateral loads on thewall depend on the height of the fill, the soil


Figure 3-2: Components of Crawl Space Structural System

WALL RESISTSLATERAL LOADFROM SOIL

SPREAD FOOTING DISTRIBUTES VERTICAL LOAD TO GROUND

ANCHOR BOLT CONNECTS FOUNDATION WALL TOSUPERSTRUCTURE ANDRESISTS WIND UPLIFT

WALL RESISTS VERTICAL LOAD FROM ABOVE-GRADESTRUCTURE

type and moisture content, and whether thebuilding is located in an area of low or highseismic activity. Some simple guidelines forwall thickness, concrete strength, andreinforcing are given in the constructiondetails that follow. Where simple limits areexceeded, a structural engineer should beconsulted.

In place of a structural foundation walland continuous spread footing, the structurecan be supported on piers or piles withbeams in between. These beams betweenpiers support the structure above andtransfer the load back to the piers.

Concrete spread footings providesupport beneath concrete and masonry crawlspace walls and/or columns. Footings mustbe designed with adequate size to distributethe load to the soil and be placed beneath themaximum frost penetration depth unlessfounded on bedrock or proven non-frost-susceptible soil or insulated to prevent frostpenetration. A compacted gravel bed servesas the footing under a wood foundation wallwhen designed in accordance with theNational Forest Products Association’s woodfoundation specification (NFPA 1987). Sincethe interior temperature of a vented crawlspace may be below freezing in very coldclimates, footings must be below the frostdepth with respect to both interior andexterior grade unless otherwise protected.



Although a crawl space foundation is notas deep as a full basement, it is highlydesirable to keep it dry. Good surfacedrainage is always recommended and, inmany cases, subsurface drainage systemsmay be desirable. The goal of surfacedrainage is to keep water away from thefoundation by sloping the ground surfaceand using gutters and downspouts for roofdrainage. Where the crawl space floor is atthe same level or above the surroundingexterior grade, no subsurface drainagesystem is required (see Figure 3-3). On siteswith a high water table or poorly drainingsoil, one recommended solution is to keep the


crawl space floor above or at the same levelas exterior grade.

On sites with porous soil and no watertable near the surface, placing the crawl spacefloor below the surface is acceptable with norequirement for a subdrainage system.Where it is necessary or desirable to place thecrawl space floor beneath the existing gradeand the soil is nonporous, a subsurfaceperimeter drainage system similar to thatused for a basement is recommended (seeFigure 3-4). In some cases a sump may benecessary. On a sloping site, subdrainagemay be required on the uphill side if the soilis nonporous. Generally no waterproofing ordampproofing on the exterior foundationwalls of crawl spaces is considered necessary,assuming drainage is adequate.


If a vented crawl space is insulated, theinsulation is always located in the ceiling.Most commonly, batt insulation is placedbetween the floor joists. The depth of thesejoist spaces accommodates high insulationlevels at a relatively low incremental cost.This placement usually leaves sill plates opento inspection for termites or decay.

A key question in the design of anunvented crawl space is whether to placeinsulation inside or outside the wall. Interms of energy use, there is not a significantdifference between the same amount ofinsulation applied to the exterior versus theinterior of a concrete or masonry wall.However, the installation costs, ease ofapplication, appearance, and varioustechnical concerns can be quite different.

Rigid insulation placed on the exteriorsurface of a concrete or masonry wall hassome advantages over interior placement inthat it can provide continuous insulationwith no thermal bridges, protect structuralwalls at moderate temperatures, andminimize moisture condensation problems.Exterior insulation at the rim joist leavesjoists and sill plates open to inspection fromthe interior for termites and decay. On theother hand, exterior insulation on the wallcan be a path for termites and can preventinspection of the wall from the exterior. Ifneeded a termite screen should be installedthrough the insulation where the sill platerests on the foundation wall. Verticalexterior insulation on a crawl space wall canextend as deep as the top of the footing and,

Figure 3-3: Crawl Space Drainage Techniques

Figure 3-4: Crawl Space Drainage Techniques

WHEN THE CRAWL SPACE FLOOR IS AT OR ABOVE EXTERIOR GRADE, A SUBSURFACE DRAINAGE SYSTEMIS NOT NECESSARY

SURFACE DRAINAGETECHNIQUES:- SLOPE GROUND AWAY- USE GUTTERS AND DOWNSPOUTS

WHEN THE CRAWL SPACE FLOOR IS BELOW EXTERIOR GRADE, A SUBSURFACE DRAINAGE SYSTEMIS RECOMMENDED IFSOIL IS NONPOROUS

SURFACE DRAINAGETECHNIQUES:- SLOPE GROUND AWAY- USE GUTTERS AND DOWNSPOUTS


inspection for termites.With a pressure-preservative-treated

wood foundation system, insulation is placedin the stud cavities similar to above-gradeinsulation in a wood frame wall. Thisapproach has a relatively low cost andprovides sufficient space for considerableinsulation thickness.

In addition to more conventional interioror exterior placement covered in thishandbook, there are several systems thatincorporate insulation into the constructionof the concrete or masonry walls. Theseinclude (1) rigid foam plastic insulation castwithin concrete walls, (2) polystyrene beadsor granular insulation materials poured intothe cavities of conventional masonry walls,(3) systems of concrete blocks with insulatingfoam inserts, (4) formed, interlocking rigidfoam units that serve as a permanentinsulating form for cast-in-place concrete,and (5) masonry blocks made withpolystyrene beads instead of aggregate in theconcrete mixture, resulting in significantlyhigher R-values. However, the effectivenessof systems that insulate only a portion of thewall area should be evaluated closely becausethermal bridges through the insulation canimpact the total performance significantly.


Techniques for controlling the entry oftermites through residential foundations areadvisable in much of the United States (seeFigure 3-5). The following recommendationsapply where termites are a potential problem.Consult with local building officials andcodes for further details.

1. Minimize soil moisture around thefoundation by using gutters and downspoutsto remove roof water, and by installing acomplete subdrainage system around thefoundation.

2. Remove all roots, stumps, and scrapwood from the site before, during, and afterconstruction, including wood stakes andformwork from the foundation area.

3. Treat soil with termiticide on all sitesvulnerable to termites.

4. Place a bond beam or course of solidcap blocks on top of all concrete masonryfoundation walls to ensure that no open cores

if desired, be supplemented by extending theinsulation horizontally from the face of thefoundation wall.

Interior crawl space wall insulation ismore common than exterior, primarilybecause it is less expensive since noprotective covering is required. On the otherhand, interior wall insulation may beconsidered less desirable than exteriorinsulation because it (1) increases theexposure of the wall to thermal stress andfreezing, (2) may increase the likelihood ofcondensation on sill plates, band joists, andjoist ends, (3) often results in some thermalbridges through framing members, and (4)may require installation of a flame spreadresistant cover. Rigid board insulation iseasier to apply to the interior wall than battinsulation since it requires no framing forsupport, is continuous, can be installed priorto backfilling against the foundation wall orinstalling the floor, and may require noadditional vapor retarder. Insulation placedaround the crawl space floor perimeter canprovide additional thermal protection;however, it may also create additional pathsfor termite entry. Batt insulation iscommonly placed inside the rim joist. Thisrim joist insulation should be covered on theinside face with a polyethylene vaporretarder or a rigid foam insulation, sealedaround the edges, to act as a vapor retarder.In place of batts, simply using tight-fittingrigid foam pieces in the spaces between thefloor joists is an effective solution.

Less expensive batts are an alternative torigid foam insulation on the interior crawlspace wall. It is possible to install them in acrawl space similar to a basementinstallation. One way is to provide a furred-out stud wall and a vapor retarder on thestuds. This is a more expensive and lesslikely approach than simply using rigid foamwith no furring. A common, low-costapproach to insulating crawl space walls issimply draping batts with a vapor retarderfacing over the inside of the wall. In moststates, codes require the batt vapor retardercover be approved with respect to flamespread. These can be laid loosely on theground at the perimeter to reduce heat lossthrough the footing. With this approach it isdifficult to maintain the continuity of thevapor retarder around the joist ends and toseal the termination of the vapor retarder.Good installations are difficult because ofcramped working conditions, and a vapor-proof installation will prevent easy


Figure 3-5: Termite Control Techniques for Crawl Spaces

PRESSURE-PRESERVATIVE TREATED SILL PLATE8-IN. MIN. ABOVE GRADE




MINIMIZE SOIL MOISTURE - USE GUTTERS AND DOWNSPOUTS - INSTALL SUBSURFACE DRAINAGE SYSTEM

BOND BEAM, CAP BLOCK,OR FILLED UPPER COURSEOF MASONRY WALL

WOOD POSTS SHOULD BE TREATED, PLACED ONFLASHING, OR PLACED ONA CONCRETE PEDESTAL8 IN. ABOVE FLOOR

are left exposed. Alternatively, fill all coreson the top course with mortar, and reinforcethe mortar joint beneath the top course.

5. Place the sill plate at least 8 inchesabove grade; it should be pressure-preservative treated to resist decay. The sillplate should be visible for inspection fromthe interior. Since termite shields are oftendamaged or not installed carefully enough,they are considered optional and should notbe regarded as sufficient defense bythemselves.

6. Be sure that exterior wood siding andtrim is at least 6 inches above the final grade.

7. Construct porches and exterior slabsso that they slope away from the foundationwall and are at least 2 inches below exteriorsiding. In addition, porches and exteriorslabs should be separated from all woodmembers by a 2-inch gap visible forinspection or by a continuous metal flashingsoldered at all seams.

8. Use pressure-preservative-treatedwood posts within a crawl space, or placeposts on flashing or on a concrete pedestalraised 8 inches above the interior grade.

Plastic foam and batt insulation materialshave no food value to termites, but they canprovide protective cover and easy tunnelling.Insulation installations can be detailed forease of inspection, although often bysacrificing thermal efficiency. In principle,termite shields offer protection throughdetailing, but should not be relied upon as abarrier.

These concerns over insulation and theunreliability of termite shields have led to theconclusion that soil treatment is the mosteffective technique to control termites withan insulated foundation. However, therestrictions on some traditionally usedtermiticides may make this option eitherunavailable or cause the substitution ofproducts that are more expensive andpossibly less effective. This situation shouldencourage insulation techniques that enhancevisual inspection and provide effectivebarriers to termites.


Construction techniques for minimizingradon infiltration into a crawl space areappropriate if there is a reasonable


probability that radon is present (see Figure3-6). To determine this, contact the statehealth department or environmentalprotection office.

1. For crawl spaces susceptible to lowradon exposure, provide substantial outsideair ventilation. Place vents on all four sidesof the crawl space. A second more reliableradon control solution is to control andisolate the source as suggested for basementconstruction in Chapter 2.

2. Place a 6-mil polyethylene vaporretarder over all exposed soil floor areas.Overlap edges 12 inches and seal. Seal edgesto the interior face of the foundation wall.

3. If the crawl space is unvented or ifindoor radon levels could be moderate tohigh, follow the radon control techniquesrecommended for basements (see Chapter 2).This may also include pressurization of thecrawl space or soil gas removal from beneaththe crawl space soil covering.

4. Construct floors above unconditionedspaces with a continuous air infiltrationbarrier. Tongue and groove plywood floordecking should be applied with butt jointscontinuously glued to floor joists with awaterproof construction adhesive. Seal allpenetrations through the subfloor with caulk.Enclose large openings such as at bath tubdrains with sheet metal or other rigidmaterial and sealants.

5. Avoid duct work in the crawl space ifpossible, but it may be installed providing alljoints are securely taped or otherwise tightlysealed.

6. Render crawl space walls separatingan attached vented crawl space from abasement or living space as airtight aspossible.

PROVIDE SUBSTANTIALOUTSIDE AIR FORVENTILATION

IF CRAWL SPACE IS UNVENTED, APPLY RADON CONTROL TECHNIQUES FORBASEMENTS (SEE FIG. 2-4)

CONSTRUCT FLOOR WITHCONTINUOUS AIR BARRIER

SEAL ALL PENETRATIONSTHROUGH FLOOR WITHCAULKING

SECURELY TAPE ALL JOINTS IN DUCTWORK - IF POSSIBLE AVOID PLACINGDUCTWORK INCRAWL SPACE

PLACE 6-MIL POLYOVER FLOOR ANDSEAL TO WALLS

Figure 3-6: Radon Control Techniques for Crawl Spaces

RIM JOIST




3.3 Crawl SpaceConstruction Details

In this section several typical crawl spacewall sections are illustrated and described.Figure 3-8 shows a typical vented crawl spacewith insulation placed in the floor joistsabove the space. In Figure 3-9 insulationplaced outside the foundation wall of anunvented crawl space is shown, whileFigures 3-10 and 3-11 show insulation placedinside the wall of an unvented crawl space.Included in this group of illustrations arevariations in construction systems and

approaches to insulating the rim joist area.Numbers that occur within boxes in eachdrawing refer to the notes on pages 53 and 54that follow the drawings (see Figure 3-7).

The challenge is to develop integratedsolutions that address all key considerationswithout unnecessarily complicating theconstruction or increasing the cost. There isno one set of perfect solutions; recommendedpractices or details often represent trade-offsand compromises. The purpose of thissection is to show and describe a variety ofreasonable alternatives. Individualcircumstances will dictate final designchoices.


1. Insulation protection: Exterior insulationmaterials should not be exposed above grade.They should be covered by a protectivematerial — such as exterior grade plastic,fiberglass, galvanized metal or aluminumflashing, a cementitious coating, or a rigidprotection board — extending at least 6 inchesbelow grade.

2. Surface drainage: The ground surfaceshould slope downward at least 5 percent (6inches) over the first 10 feet surrounding thebasement wall to direct surface runoff awayfrom the building. Downspouts and guttersshould be used to collect roof drainage anddirect it away from the foundation walls.

Page 48 Chapter 3—Crawl Space Construction



Figure 3-8: Vented Crawl Space Wall with Ceiling Insulation

RIM JOIST


CRAWL SPACE VENT AT TOP OF FOUNDATION WALL 21


EXTERIOR SIDING

SHEATHING

CONCRETE FOOTING 8

REINFORCING(OPTIONAL) 19

BATT INSULATION BETWEEN FLOOR JOISTS WITH VAPORRETARDER ON TOP 20



CONTINUOUS VAPORDIFFUSION RETARDER(GROUND COVER) 18


VAPOR RETARDER

INSULATION IN 2 x 4 WALL

SUBFLOOR

7-IN.MIN.

24-IN. 17

Figure 3-8 illustrates a ventedcrawl space with a concretefoundation wall. Theinsulation is placed betweenthe floor joists over the crawlspace. The crawl space floor isat the same level as thesurrounding grade resulting inno major drainage concerns.


Figure 3-9 illustrates anunvented crawl space with aconcrete masonry foundationwall. The exterior insulationis covered by a flashing at thetop. There is no limit to thethickness of insulation that canbe used with this approach.The crawl space floor is belowthe level of the surroundinggrade. A perimeter drainagesystem is shown.

CONCRETE FOOTING 8


EXTERIOR SIDING

SHEATHING

FLASHING COVERSTOP OF INSULATION

PROTECTION BOARD, COATING 1

RIGID INSULATION 5

RIM JOIST




FILTER FABRIC ABOVE GRAVEL (OPTIONAL ON SIDES ANDBELOW) 6

COARSEGRAVEL(OPTIONAL)


1/2-IN. ANCHOR BOLTS AT 6 FT. O. C. MAX.EMBEDDED 7 TO 15 IN. AS REQUIRED BY CODE 23

FILLED BLOCK CORESOR BOND BEAM 22

CONCRETE MASONRY FOUNDATION WALL 14

VAPOR RETARDER 18


VAPOR RETARDER


SUBFLOOR

CAULKING (OPTIONAL) 9

PRESSURE-TREATED SILL PLATE 11

GASKET UNDER SILL PLATE

8-IN. MIN.

24-IN. 17

Figure 3-9: Unvented Crawl Space Wall with Exterior Insulation


Figure 3-10: Unvented Crawl Space Wall with Interior Insulation

EXTERIOR SIDING

SHEATHING



COARSEGRAVEL


1/2-IN. ANCHOR BOLTS AT 6 FT. O. C. MAX. 12

RIGID INSULATION 15


VAPOR RETARDER 18

RIGID INSULATION MAY EXTEND HORIZONTALLY ON FLOOR (OPTIONAL)


VAPOR RETARDER


SUBFLOOR





CONCRETE FOOTING 8


BATT INSULATION

RIGID INSULATION CAULKED AT ALL EDGES FORMS VAPOR RETARDER (OPTIONAL) 10

8-IN.MIN.

24-IN. 17

Figure 3-10 illustrates anunvented crawl space with aconcrete foundation wall.Rigid insulation is placedvertically on the interior.There is no limit to thethickness of insulation that canbe used with this approach.The crawl space floor is belowthe level of the surroundinggrade. A perimeter drainagesystem is shown.


EXTERIOR SIDING

SHEATHING



COARSEGRAVEL


1/2-IN. ANCHOR BOLTS AT 6 FT. O. C. MAX. 12

VAPOR RETARDER EXTENDS ABOVE GRADE ON WALL (OPTIONAL) 18


FIBERGLASS INSULATION WITH VAPOR RETARDER ON INSIDE 16


VAPOR RETARDER


SUBFLOOR





VAPOR RETARDER 18

CONCRETE FOOTING 8


BATT INSULATION

VAPOR RETARDER SEALED TO SUBFLOOR AND FLOOR JOISTS 16

8-IN.MIN.

24-IN. 17

Figure 3-11: Unvented Crawl Space Wall with Interior Insulation

Figure 3-11 illustrates anunvented crawl space with aconcrete foundation wall. Battinsulation is placed verticallyon the interior wall andextends horizontally onto theperimeter of the floor. Thecrawl space floor is below thelevel of the surrounding grade.A perimeter drainage system isshown.


NOTES FOR ALL DETAILEDCRAWL SPACE DRAWINGS(FIGURES 3-8 THROUGH 3-11)

1. Insulation protection: Exterior insulationmaterials should not be exposed above grade. Theabove-grade portion should be covered by aprotective material — such as exterior grade plastic,fiberglass, galvanized metal or aluminum flashing, acementitious coating, or a rigid protection board —extending at least 6 inches below grade.

2. Surface drainage: The ground surface shouldslope downward at least 5 percent (6 inches) over thefirst 10 feet surrounding the crawl space wall to directsurface runoff away from the building. Downspoutsand gutters should be used to collect roof drainageand direct it away from the foundation walls.

3. Backfill cover: Backfill around the foundationshould be covered with a low permeability soil, or amembrane beneath the top layer of soil, to divertsurface runoff away from the foundation. (Optional)

4. Backfill or drainage materials: When the crawlspace floor is below exterior grade, porous backfillsand or gravel should be used against the walls topromote drainage. Backfill should be compacted sothat settlement is minimized. In place of porousbackfill, a drainage mat material or insulatingdrainage board can be placed against the foundationwall. The drainage mat should extend down to adrainpipe at the footing level. (Optional)

5. Exterior insulation materials: Acceptablematerials for exterior insulation are: (1) extrudedpolystyrene boards (XEPS) under any condition,(2) molded expanded polystyrene boards (MEPS) forvertical applications when porous backfill andadequate drainage are provided, and (3) fiberglass orexpanded polystyrene drainage boards. The portionabove grade could be polyurethane or MEPS.

6. Filter fabric: Where a drainage system is used, afilter fabric over the gravel bed and drainpipe isrecommended to prevent clogging of the drainagearea with fine soil particles. Wrapping the filter fabricaround the entire gravel bed is an optional techniquefor better protection against clogging.

7. Drainage system: Where porous soils arepresent and drainage problems are not anticipated,no subdrainage system is necessary. Whereconditions warrant and the crawl space floor is belowthat of the exterior grade, a gravel drainage systemshould be installed. An optional 4-inch-diameterperforated drainpipe may be installed in the gravel.Perforated drainpipes should be placed with holesfacing downward alongside the footing on either theoutside or inside. Outside placement is preferred fordrainage but inside placement is less susceptible tofailure. Drainpipes should slope 1 inch in 20 feet andlead to an outfall or sump. A vertical clean-out pipewith an above-grade capped end is recommended toflush out the system. The pipe should be surroundedby at least 6 inches of gravel on the sides and 4inches of gravel above and below the pipe. Surfaceor roof drainage systems should never be connectedto the subsurface drainage system. (Optional)

8. Concrete footing: All concrete footings must bedesigned with adequate size to distribute the load tothe soil and be placed beneath the maximum frostpenetration depth unless founded upon bedrock orproven non-frost-susceptible soil, or insulated toprevent frost penetration. Concrete used in spreadfootings should have a minimum compressivestrength of 2500 psi.

9. Caulking: Caulking at the following interfaces willminimize air leakage: foundation wall/sill plate, sillplate/rim joist, rim joist/subfloor, subfloor/above-gradewall plate. An alternative is to cover these points onthe exterior with an air barrier material. (Optional)

10. Insulation inside rim joist: Insulation can beplaced on the inside of the rim joist but with greaterrisk of condensation problems and less access towood joists and sills for inspection from the interior.Low permeability rigid insulation (such as extrudedpolystyrene) should be used, or a vapor retardershould be placed on the inside of the insulation andsealed to all surrounding surfaces.

11. Sill plate: The sill plate should be at least 8inches above grade and should be pressure-preservative treated to resist decay.

12. Anchor bolts for concrete walls: Anchor boltsshould be embedded in the top of concretefoundation walls. Most codes require bolts of 1/2-inch minimum diameter to be embedded at least 7inches into the wall. Generally, anchor bolts can beplaced at a maximum spacing of 6 feet and no furtherthan 1 foot from any corner.

13. Cast-in-place concrete wall: Concrete used inthe wall should have a minimum compressivestrength of 2500 psi with a 4- to 6-inch slump. Noadditional water should be added at the job site.Generally, where there are stable soils in areas of lowseismic activity, no reinforcing is required in a 6-inch-thick basement wall with up to 4 feet of fill.

14. Masonry wall: Generally, where there arestable soils in areas of low seismic activity, noreinforcing is required in an 8-inch-thick masonry wallwith up to 4 feet of fill. When reinforcing is required, itmust be grouted into block cores. Vertical barsshould be spaced no more than 48 inches apart or 6times the wall thickness, whichever is less.

15. Interior rigid insulation materials: Acceptablematerials for placement inside a crawl space wallinclude (1) extruded polystyrene boards (XEPS) and(2) expanded polystyrene boards (MEPS). Anignition barrier may be required for some of thesematerials for fire protection.

16. Interior fiberglass batt insulation: Fiberglassbatts can be draped over the wall and laid loosely onthe ground at the crawl space perimeter. Specialcare is necessary to maintain continuity of the vaporretarder on the insulation face. If left exposed thebatts should have “low flame spread” facing.

17. Crawl space height: There should be adequatespace under all beams, pipes, and ducts to allow aperson to access all areas of the crawl space, andespecially the perimeter. Leaving adequate spacealso prevents ventilation from being impeded. Codesand standard practice guides usually call for aminimum of 18 inches between the crawl space floor


and the underside of the joists, but this is ofteninadequate after ducts and plumbing are installed.Instead, a minimum of 24 inches under the joists isadvisable. An access way into the crawl space mustalso be provided.

18. Vapor retarder (ground cover): In regions with20 inches or more annual precipitation or if radonmitigation is necessary, a 6-mil polyethylene vaporretarder should be placed over the entire crawl spacefloor. All debris must be removed and the soil leveledbefore laying the membrane. Edges of themembrane should be lapped 12 inches. No sealing isrequired for moisture but is suggested for radonmitigation. It is not necessary to carry the groundcover membrane up the face of the wall unless theinterior grade is below that outside, or radon is ofparticular concern. A membrane on the wall helpsconfine water that may leak through the wall to theunderside of the membrane on the floor.

19. Reinforcing in footing: Reinforcing bars placed2 inches below the top of the footing running parallelto the wall are recommended where differentialsettlement is a potential problem. (Optional)

20. Ceiling insulation: Insulation is placed in thecrawl space ceiling when the space is vented. Withfiberglass insulation placed between the wood joists,the vapor retarder should be above the insulation.

21. Vent requirements: A rectangular crawl spacerequires a minimum of four vents, one on each wall,located no farther than 3 feet from each corner. Thevents should be as high on the wall as possible butbelow the floor insulation to best capture breezes,and landscaping should be planned to preventobstruction of the vents. The total free (open) area ofall vents should be no less than 1/1500 of the floorarea. The gross area of vents required depends onthe type of vent. In the absence of a ground cover,the vent area should be increased to 1/150 of thefloor area. Ventilation alone should not be reliedupon where soils are known to be moist.

22. Bond beam on masonry wall: When requiredby code or a structural engineer, a bond beamprovides additional lateral strength in a masonry wall.Using a bond beam or filling the cores of the uppercourse of block also are recommended as radon andtermite prevention techniques. (Optional)

23. Anchor bolts for masonry walls: Anchor boltsshould be embedded in the top of masonryfoundation walls. Most codes require bolts of 1/2-inch minimum diameter embedded at least 7 inchesinto the wall. In some locations, codes require boltsto be embedded 15 inches in masonry walls to resistuplift. To provide adequate anchorage in a masonrywall, bolts either must be embedded in a bond beamor the appropriate cores of the upper course of blockmust be filled with mortar. Generally, anchor boltscan be placed at a maximum spacing of 6 feet and nofurther than 1 foot from any corner.


3.4 Checklist for Design and Construction ofCrawl Space Foundations


OVERALL

General considerations. Under adverse conditions, crawl spaces should be designedwith the same drainage measures as basements. All areas of the crawl space must beaccessible for inspection of pipes, ducts, insulation, sill plates, rim joists, posts, etc. A crawlspace floor above exterior grade is preferred for positive drainage.

____ ____ Provide access into crawl space____ ____ Provide clearance under floor structure and ducts to provide access to

entire perimeter____ ____ Call for trenches under girders and ducts to allow passage____ ____ Use 2-inch slurry slab (vermin control and ground cover protection)____ ____ Locate footing frost depth with respect to interior for well-vented recessed

crawl spaces____ ____ Consider optional floor drain

SITEWORK







FOOTINGS

____ ____ Position bottom of footing at least 6 inches below frost depth aroundperimeter (frost wall at garage, slabs supporting roofs, other elementsattached to structure). Make sure footing is deeper under basementwalkouts


plan____ ____ Use keyway or steel dowels to anchor walls____ ____ Dimension stepped footings according to local codes and good practice

(conform to masonry dimensions if applicable)____ ____ Provide weep holes (minimum 2-inch diameter at 4 feet to 8 feet on center)____ ____ Provide through-joint flashing as a capillary break

STRUCTURAL DESIGN

General considerations. Walls with high unbalanced fill should be designed as abasement.

Confirm wall engineering and accessories:

____ ____ Wall sized to resist height of fill and seismic loads____ ____ Anchor bolt requirements for sill plate (minimum code)____ ____ Anchors for joist ends (typically 6-foot spacing)____ ____ Beam pocket elevations, dimensions, details____ ____ Top of wall elevations and changes in wall height____ ____ Brick shelf widths and elevations

Determine concrete specifications:

____ ____ Minimum compressive strength after 28 days____ ____ Maximum water/cement ratio. Note: add no water at site____ ____ Allowable slump____ ____ Acceptable and unacceptable admixtures____ ____ Curing requirements (special hot, cold, dry conditions)____ ____ Two-way reinforcing____ ____ No. 5 bars at top and bottom of wall to resist settlement cracking (for

termite resistance)

Determine concrete masonry wall specifications:

____ ____ Specify mortar mixes and strengths____ ____ Special details for proprietary masonry systems____ ____ Use either bond beam or joint reinforcing for crack control (for termite

resistance)____ ____ Use special measures for high termite hazard areas

CRAWL SPACE CHECKLIST (PAGE 2 OF 4)


THERMAL AND VAPOR CONTROLS

General considerations. Vented crawl spaces are insulated in the ceiling, and enclosedcrawl spaces are insulated either inside or outside the wall. Ceiling insulation requiresinsulating ducts and plumbing. Wall insulations require special moisture control measuresand may conceal termite infestations. Exterior insulation may reduce condensation hazard atrim joists.

____ ____ Confirm that wall or ceiling insulation R-value meets local codes and/orrecommendations provided by this handbook

____ ____ If used, specify exterior insulation product suitable for in-ground use____ ____ Cover exterior insulation above grade with a protective coating

DECAY AND TERMITE CONTROL


____ ____ Locate and specify foundation vents____ ____ Install ground cover vapor retarder____ ____ Elevate interior wood posts on concrete pedestals____ ____ Locate floor (area) and footing drains if crawl space floor is below exterior

grade (see Subdrainage under basement checklist in chapter 2)____ ____ Pressure-treat wood posts, sill plates, rim joists, wood members in contact

with foundation piers, walls, floors, etc.____ ____ Pressure-treat all outdoor weather-exposed wood members____ ____ Install dampproof membrane under sill plate and beams in pockets

(flashing or sill seal gasket)____ ____ Leave minimum 1/2-inch air space around beams in beam pockets____ ____ Expose sill plates and rim joists for inspection____ ____ Elevate sill plate minimum 8 inches above exterior grade____ ____ Elevate wood posts and framing supporting porches, stairs, decks, etc.,



clearance for drainage and termite inspection (or provide properflashing)

____ ____ Pitch porches, decks, patios for drainage (minimum 1/4 in/ft)____ ____ Treat soil with termiticide, especially with insulated foundations



RADON CONTROL MEASURES

General considerations. The potential for radon hazard is present in all buildings.Check state and local health agencies for need of protection. Strategies: (1) barriers; (2) airmanagement; (3) provisions to simplify retrofit. Since radon is a gas, its rate of entry throughthe foundation depends on suction due to stack effect and superstructure air leakage.

____ ____ Separate outdoor intakes for combustion devices____ ____ Install air barrier wrap around superstructure____ ____ Seal around flues, chases, vent stacks, attic stairs____ ____ Install polyethylene vapor retarder as floor underlayment between first

floor and crawl space


____ ____ Complete plans and specs____ ____ Bid package____ ____ Contractual arrangements (describe principals, describe the work by

referencing the blueprints and specs, state the start/completion dates,price, payment schedule, handling of change orders, handling ofdisputes, excavation allowance, and procedure for firing)

____ ____ Building permits


____ ____ After excavation and before concrete is poured for the footings____ ____ After the footings have been poured before foundation wall construction____ ____ After foundation construction and dampproofing before rough framing____ ____ After rough framing____ ____ After rough plumbing____ ____ After rough electrical____ ____ After insulation installation before drywall and backfilling in case of




This chapter summarizes the majorrecommendations and practices related toslab-on-grade foundation design. Section 4.1shows typical recommended levels ofinsulation for each of five representative U.S.climates.

Section 4.2 summarizes design andconstruction practices covering the followingareas: structural aspects, location ofinsulation, drainage, termite and wood decaycontrol, and radon control. Section 4.3includes a series of alternative constructiondetails with accompanying notes indicatingspecific practices. Section 4.4 is a checklist tobe used during the design and constructionof a slab-on-grade foundation.

4.1 Slab-on-GradeInsulation Placement andThickness

To provide energy use information forbuildings with slab-on-grade foundations,heating and cooling loads were simulated fordifferent insulation placements andthicknesses in a variety of U.S. climates (Labset al. 1988). Key assumptions are that theinterior space above the slab is heated to atemperature of 70OF and cooled to atemperature of 78OF when required.

Insulation Configurations and Costs

Table 4-1 includes illustrations anddescriptions of a variety of slab-on-gradeinsulation configurations. The constructionsystem in all cases is a concrete (or masonry)

Figure 4-1: Slab-on-Grade Foundationwith Exterior Insulation

CHAPTER 4

Slab-on-Grade Construction

Chapter 4—Slab-on-Grade Construction


EXTERIOR VERTICAL

INTERIOR VERTICAL

INTERIOR HORIZONTAL

A: Concrete or Masonry Foundation Wall with Exterior Insulation Placed Vertically

C: Concrete or Masonry Foundation Walls with Interior Insulation Placed Horizontally Under Slab Perimeter

NO INSULATION

2 FT DEEP: R-5

2 FT DEEP: R-10

4 FT DEEP: R-5

4 FT DEEP: R-10

4 FT DEEP: R-15

4 FT DEEP: R-20

NO INSULATION

2 FT DEEP: R-5

2 FT DEEP: R-10

4 FT DEEP: R-5

4 FT DEEP: R-10

4 FT DEEP: R-15

4 FT DEEP: R-20

NO INSULATION

2 FT WIDE: R-5

2 FT WIDE: R-10

4 FT WIDE: R-5

4 FT WIDE: R-10

B: Concrete or Masonry Foundation Walls with Interior Insulation Placed Vertically

EXTERIOR HORIZONTAL

D: Concrete or Masonry Foundation Walls with Exterior Insulation Extending Outward Horizontally

NO INSULATION

2 FT WIDE: R-5

2 FT WIDE: R-10

4 FT WIDE: R-5

4 FT WIDE: R-10

0-2000 HDD(LOS ANG)



6-8000 HDD(CHICAGO)

8-10000 HDD(MPLS)



Table 4-1: Insulation Recommendations for Slab-on-Grade Foundations



foundation wall extending either 2 or 4 feetdeep with the upper 8 inches of thefoundation wall exposed on the exterior.

The three most common approaches toinsulating slab-on-grade foundations withconcrete/masonry walls are (1) placinginsulation vertically on the entire exteriorsurface of the foundation wall (2 or 4 feetdeep), (2) placing insulation vertically on theentire interior surface of the foundation wall(2 or 4 feet deep), and (3) placing insulationhorizontally under the slab perimeter(extending 2 or 4 feet). When insulation isplaced either vertically or horizontally on theinterior, it is important to place insulation inthe joint between the slab edge andfoundation wall. It is not necessary to placemore than R-5 insulation in this joint. Forexample, even when R-15 insulation isrecommended for the foundation wall, onlyR-5 insulation in the joint proves to be cost-effective.

In addition to these conventionalapproaches, some cases were simulatedwhere insulation is placed horizontally onthe building exterior (extending either 2 or 4feet into the surrounding soil). In someregions it is common practice to have ashallower footing than 2 feet or have nofoundation wall at all—just a thickened slabedge. In these cases, a full 2 feet of verticalinsulation is not an option; however,additional horizontal insulation placementon the exterior is possible.


While increasing the amount offoundation insulation produces greaterenergy savings, the cost of installation mustbe compared to these savings. Such acomparison can be done in several ways;however, a life cycle cost analysis (presentedin worksheet form in chapter 5) is

recommended since it takes into account anumber of economic variables includinginstallation costs, mortgage rates, HVACefficiencies, and fuel escalation rates. Inorder to identify the most economicalamount of insulation for the crawl spaceconfigurations shown in Table 4-1, the casewith the lowest 30-year life cycle cost wasdetermined for five U.S. cities at threedifferent fuel cost levels. See the BuildingFoundation Design Handbook (Labs et al. 1988)to find recommendations for a greaternumber of cities and for a detailedexplanation of the methodology. Theeconomic methodology used to determinethe insulation levels in Table 3-1 is consistentwith ASHRAE standard 90.2P. The simplepayback averages 13 years for all U.S. climatezones, and never exceeds 18 years for any ofthe recommended levels.

Economically optimal configurations areshown by the darkened circles in Table 4-1 inthe following categories: (1) exteriorinsulation placed vertically on the foundationwall, (2) interior insulation placed verticallyon the foundation wall, (3) interior insulationplaced horizontally beneath the slabperimeter, and (4) exterior insulationextending outward horizontally from thefoundation wall. Configurations arerecommended for a range of climates andfuel prices in each of these categories, but thedifferent categories of cases are not directlycompared with each other. In other words,there is an optimal amount of exteriorvertical insulation recommended for a givenclimate and fuel price, and there is a differentoptimal amount of interior insulation placedvertically. Where there is no darkened circlein a particular category, insulation is noteconomically justified under the assumptionsused.

Exterior vertical insulation ranging fromR-5 to R-10 is justified in all climate zones

Table 4-2: Fuel Price Levels Used to Develop Recommended Insulation Levels in Table 4-1


NATURAL GAS

FUEL OIL

PROPANE

HEATING

COOLING ELECTRICITY

.374 / THERM

.527 / GALLON

.344 / GALLON

.051 / KWH

.561 / THERM

.791 / GALLON

.516 / GALLON

.076 / KWH

.842 / THERM

1.187 / GALLON

.775 / GALLON

.114 / KWH


except the warmest one. As the climatebecomes colder and fuel prices increase, therecommended R-value and depth ofinsulation increase as well. Similar levels ofinterior insulation are recommended for bothvertical and horizontal placement. Forexterior insulation extending outwardhorizontally, a 2-foot-wide section of R-5insulation is recommended at all fuel pricelevels and in all climate zones except thewarmest one.

It should be noted that for all cases withinterior vertical or horizontal insulation, it isassumed that R-5 insulation is placed in thegap between the slab edge and thefoundation wall. A simulation with noinsulation in the gap indicates that energysavings are reduced by approximately 40percent, compared with a similarconfiguration with the R-5 slab edgeinsulation in place.

Comparison of Insulation Approaches

When exterior and interior verticalinsulation are compared, thermal results arevery similar for equivalent amounts ofinsulation. Since it is assumed that exteriorinsulation costs more to install, however,interior placement is always economicallyoptimal in comparison. This increased costfor an exterior insulation is attributed to theneed for protective covering.

Interior insulation placed horizontallybeneath the slab perimeter performs almostidentically to interior vertical insulation interms of energy savings. However, interiorvertical insulation is slightly more cost-effective than placement beneath the slabperimeter because the installation cost of thehorizontal approach is slightly higher(although not as high as exterior verticalinsulation).

Exterior horizontal insulation actuallysaves more energy for an equivalent amountof insulation compared with the otheralternatives; however, it is the least cost-effective approach. In fact, exteriorhorizontal insulation is not directlycomparable to the other cases since it actuallyrequires an extra foot of vertical insulationbefore it extends horizontally. Thus, costs arehigher due to the protective cover as well asthe additional amount of material.

In spite of the apparent cost-effectivenessof interior vertical insulation compared withthe other approaches, this is only one ofmany cost and performance issues to be

considered. The economic benefit of interiorvertical insulation may be offset by otherpractical, performance, and aestheticconsiderations discussed elsewhere in thisbook.

Assumptions


The total installed costs for all insulationsystems considered in this analysis areshown in Table 5-2 in chapter 5. Installationcosts used in this analysis are based onaverage U.S. costs in 1987. Costs includelabor and materials for extruded polystyreneinsulation and the required protectivecovering and flashing above grade (for theexterior cases). All costs include a 30 percentbuilder markup and a 30 percentsubcontractor markup for overhead andprofit.

If the general assumptions used in thisanalysis are satisfactory for the specificproject, the reader can determine theapproximate recommended insulation levelfor a location by finding the heating degreedays from Table 5-1 in chapter 5 andselecting the appropriate climate zone andfuel price level shown in Table 4-1. If not,project-specific optimal insulation levels canbe determined using actual estimatedconstruction costs with the worksheetprovided in chapter 5. The worksheetenables the user to select economic criteriaother than allowing maximum simplepaybacks of 18 years. In addition, the usercan incorporate local energy prices, actualinsulation costs, HVAC efficiencies, mortgageconditions, and fuel escalation rates. Cost-effectiveness can vary considerably,depending on the construction details andcost assumptions.



STRUCTURAL DESIGN

The major structural components of aslab-on-grade foundation are the floor slabitself and either grade beams or foundationwalls with footings at the perimeter of theslab (see Figures 4-2 and 4-3). In some casesadditional footings (often a thickened slab)are necessary under bearing walls or columnsin the center of the slab. Concrete slab-on-grade floors are generally designed to havesufficient strength to support floor loadswithout reinforcing when poured onundisturbed or compacted soil. The properuse of welded wire fabric and concrete with alow water/cement ratio can reduce shrinkagecracking, which is an important concern forappearance and for reducing potential radoninfiltration.

Foundation walls are typicallyconstructed of cast-in-place concrete orconcrete masonry units. Foundation wallsmust be designed to resist vertical loads fromthe structure above and transfer these loadsto the footing. Concrete spread footings mustprovide support beneath foundation wallsand columns. Similarly, grade beams at theedge of the foundation support thesuperstructure above. Footings must bedesigned with adequate bearing area todistribute the load to the soil and be placedbeneath the maximum frost penetrationdepth or be insulated to prevent frostpenetration.



Good surface drainage techniques arealways recommended for slab-on-gradefoundations (see Figure 4-4). The goal ofsurface drainage is to keep water away fromthe foundation by sloping the ground surfaceand using gutters and downspouts for roofdrainage. Because a slab-on-grade floor isabove the surrounding exterior grade, no

SLAB SUPPORTS FLOOR LOAD

GRADE BEAM DISTRIBUTES VERTICAL LOAD FROM ABOVE-GRADE STRUCTURETO GROUND


Figure 4-3: Structural Components of Slab-on-GradeFoundation with Stem Wall and Footing

SLAB SUPPORTS FLOOR LOAD

SPREAD FOOTINGDISTRIBUTES VERTICALLOAD TO GROUND

FOOTING MUST BE BELOW MAXIMUMFROST PENETRATIONDEPTH

WALL RESISTS VERTICAL LOAD FROM ABOVE-GRADE STRUCTURE


Figure 4-2: Structural Components of Slab-on-GradeFoundation with Grade Beam


layer above the surrounding ground. Themost intense heat losses are through thissmall area of foundation wall above grade, soit requires special care in detailing andinstallation. Heat is also lost from the slab tothe soil, through which it migrates to theexterior ground surface and the air. Heatlosses to the soil are greatest at the edge, anddiminish rapidly with distance from it. Bothcomponents of the slab heat loss — at theedge and through the soil — must beconsidered in designing the insulationsystem.

Insulation can be placed verticallyoutside the foundation wall or grade beam.This approach effectively insulates theexposed slab edge above grade and extendsdown to reduce heat flow from the floor slabto the ground surface outside the building.Vertical exterior insulation is the onlymethod of reducing heat loss at the edge ofan integral grade beam and slab foundation.A major advantage of exterior insulation isthat the interior joint between the slab andfoundation wall need not be insulated, whichsimplifies construction. Several drawbacks,however, are that rigid insulation should becovered above grade with a protective board,coating, or flashing material, and with brickfacings, a thermal short can be created thatbypasses both the foundation and above-grade insulation. A limitation is that thedepth of the exterior insulation is controlledby the footing depth. Additional exteriorinsulation can be provided by extendinginsulation horizontally from the foundationwall. Since this approach can control frostpenetration near the footing, it can be used toreduce footing depth requirements undercertain circumstances. This can substantiallyreduce the initial foundation constructioncost.

Insulation also can be placed verticallyon the interior of the foundation wall orhorizontally under the slab. In both cases,heat loss from the floor is reduced and thedifficulty of placing and protecting exteriorinsulation is avoided. Interior verticalinsulation is limited to the depth of thefooting but underslab insulation is notlimited in this respect. Usually the outer 2 to4 feet of the slab perimeter is insulated butthe entire floor may be insulated if desired.

It is essential to insulate the joint betweenthe slab and the foundation wall wheneverinsulation is placed inside the foundationwall or under the slab. Otherwise, asignificant amount of heat transfer occursthrough the thermal bridge at the slab edge.

Figure 4-4: Drainage Techniques for Slab-on-GradeFoundations

SURFACE DRAINAGE TECHNIQUES:

- SLOPE GROUND AWAY

- USE GUTTERS AND DOWNSPOUTS

GRAVEL DRAINAGE LAYER RECOMMENDED BENEATHSLAB IF A HIGH WATER TABLE IS PRESENT

NO SUBSURFACEDRAINAGE REQUIRED

subsurface drainage system or waterproofingis required. On sites with a high water table,the floor should be raised above existinggrade as much as possible and a layer ofgravel can be placed beneath the slab toensure that drainage occurs and moistureproblems are avoided.


Good construction practice demandselevating the slab above grade by no lessthan 8 inches to isolate the wood framingfrom rain splash, soil dampness, andtermites, and to keep the subslab drainage


The insulation is generally limited to no morethan 1 inch in thickness at this point. Boththe American Concrete Institute (1985) andthe Building Research Advisory Board (1968)recommend against pouring the slab on ashelf formed in the foundation wall,regardless of whether or not the joint isinsulated or an expansion joint is provided.

A solution to designing this floor/walljoint is shown in Figure 4-10 for a cast-in-place concrete foundation wall. The notchedwall section permits 1 inch of rigid insulationto be placed in the joint and also permits theslab to move vertically. This detail can beused for vertical interior or subslabinsulation. Concrete masonry foundationwalls are more difficult to resolvesuccessfully. Figures 4-14 and 4-15 illustratetwo solutions. The detail in Figure 4-14 uses a6-inch-thick block on the top course thatpermits insulation in the joint and verticalmovement of the slab. This detail is designedfor a 2-by-6 above-grade wall. In Figure 4-15a similar detail with a 2-by-4 above-gradewall on a 4-inch-thick block on the top courseis shown. This last alternative effectivelyprovides insulation in the joint but divergesfrom ideal structural practice. The slab restson a ledge and becomes thinner near theinsulated edge.

Another option for insulating a slab-on-grade foundation is to place insulation abovethe floor slab. A wood floor deck can beplaced on sleepers, leaving cavities that canbe filled with rigid board or batt insulation,or a wood floor deck can be placed directlyon rigid insulation above the slab. Thisapproach avoids some of the constructiondetail problems inherent in the moreconventional approaches discussed above,but may lead to greater frost depth in thevicinity of the slab edge.


Techniques for controlling the entry oftermites through residential foundations arenecessary in much of the United States (seeFigure 4-5). Consult with local buildingofficials and codes for further details.

1. Minimize soil moisture around thefoundation by surface drainage and by usinggutters, downspouts, and runouts to removeroof water.

2. Remove all roots, stumps, and wood

from the site. Wood stakes and form workshould also be removed from the foundationarea.

3. Treat soil with termiticide on all sitesvulnerable to termites (Labs et al. 1988).

4. Place a bond beam or course of solidcap blocks on top of all concrete masonryfoundation walls to ensure that no open coresare left exposed. Alternatively, fill all coreson the top course with mortar. The mortarjoint beneath the top course or bond beamshould be reinforced for additionalinsurance.

5. Place the sill plate at least 8 inches

PRESSURE-PRESERVATIVE TREATED SILL PLATE8-IN. MIN. ABOVE GRADE




MINIMIZE SOIL MOISTUREUSING SURFACE DRAINAGE TECHNIQUES - USE GUTTERS AND DOWNSPOUTS - SLOPE GROUND AWAY

BOND BEAM, CAP BLOCK, OR FILLED UPPER COURSEOF MASONRY WALL

FILL JOINT WITH CAULKING

Figure 4-5: Termite Control Techniques forSlab-on-Grade Foundations


8. Fill the joint between a slab-on-gradefloor and foundation wall with liquid-pouredurethane caulk or coal tar pitch to form atermite and radon barrier.


The following techniques for minimizingradon infiltration through a slab-on-gradefoundation are appropriate where there is areasonable probability that radon may bepresent (see Figure 4-6). To determine this,contact the state health department orenvironmental protection office.

1. Use solid pipes for floor dischargedrains to daylight or provide mechanicaltraps if they discharge to subsurface drains.

2. Lay a 6-mil polyethylene film on topof the gravel drainage layer beneath the slab.This film serves both as a radon and moistureretarder. Slit an “x” in the polyethylenemembrane at penetrations. Turn up the tabsand tape them. Care should be taken toavoid unintentionally puncturing the barrier;consider using riverbed gravel if available ata reasonable price. The round riverbedgravel allows for freer movement of the soilgas and has no sharp edges to penetrate thepolyethylene. The edges should be lapped atleast 12 inches. The polyethylene shouldextend over the top of the foundation wall, orextend to the outer bottom edge of amonolithic slab-grade beam or patio. Useconcrete with a low water/cement ratio tominimize cracking. A 2-inch-thick sand layeron top of the polyethylene improves concretecuring and prevents the concrete frominfiltrating the aggregate base under the slab.The sand should be dampened, but notsaturated, before the concrete is poured. Thesand will also offer some puncture protectionfor the polyethylene during the concretepouring operation.

3. Provide an isolation joint between thefoundation wall and slab floor where verticalmovement is expected. After the slab hascured for several days, seal the joint bypouring polyurethane or similar caulk intothe 1/2-inch channel formed with aremovable strip. Polyurethane caulks adherewell to masonry and are long-lived. They donot stick to polyethylene. Do not use latexcaulks.

above grade; it should be pressure-preservative treated to resist decay. Sincetermite shields are often damaged or notinstalled carefully enough, they areconsidered optional and should not beregarded as sufficient defense by themselves.

6. Be sure that exterior wood siding andtrim are at least 6 inches above grade.

7. Construct porches and exterior slabsso that they slope away from the foundationwall, are reinforced with steel or wire mesh,usually are at least 2 inches below exteriorsiding, and are separated from all woodmembers by a 2-inch gap visible forinspection or a continuous metal flashingsoldered at all seams.

Figure 4-6: Radon Control Techniques for Slab-on-GradeFoundations

SEAL AROUND ALL DUCTS AND PIPES IN SLAB

USE SOLID DRAINPIPES IN FLOOR WITH MECHANICALTRAPS

BOND BEAM, CAP BLOCK, OR FILLED UPPER COURSEOF MASONRY WALL

FILL JOINT WITH CAULKING

REINFORCE SLAB AND USECONCRETE WITH LOW WATER/ CEMENT RATIO TOREDUCE CRACKING

6-MIL POLY LAYERUNDER SLABEXTENDED OVER TOP OF FOUNDATIONWALL


4. Install welded wire in the slab toreduce the impact of shrinkage cracking.Consider control joints or additionalreinforcing near the inside corner of “L”shaped slabs. Two pieces of No. 4 reinforcingbar, 3 feet long and on 12-inch centers, acrossareas where additional stress is anticipated,should reduce cracking. Use of fibers withinconcrete will also reduce the amount ofplastic shrinkage cracking.

5. Control joints should be finished witha 1/2-inch depression. Fill this recess fullywith polyurethane or similar caulk.

6. Minimize the number of pours toavoid cold joints. Begin curing the concreteimmediately after the pour, according torecommendations of the American ConcreteInstitute (1980; 1983). At least three days arerequired at 70OF, and longer at lowertemperatures. Use an impervious cover sheetor wetted burlap.

7. Form a gap of at least 1/2-inch widtharound all plumbing and utility lead-insthrough the slab to a depth of at least 1/2inch. Fill with polyurethane or similarcaulking.

8. Place HVAC condensate drains so thatthey run to daylight outside the buildingenvelope. Condensate drains that connect todry wells or other soil may become directconduits for soil gas, and can be a majorentry point for radon.

9. Place a solid brick course, bond beam,or cap block on top of all masonry foundationwalls to seal cores, or fill open block cores inthe top course with concrete. An alternativeapproach is to leave the masonry cores openand fill solid at the time the floor slab is castby flowing concrete into the top course ofblock.

Intercepting Soil Gas

At this time the best strategy formitigating radon hazard seems to be toreduce stack effects by building a tightfoundation in combination with a generallytight above-grade structure, and to make surea radon collection system and, at the veryleast, provisions for a discharge system arean integral part of the initial construction.This acts as an insurance policy at modestcost. Once the house is built, if radon levelsare excessive, a passive discharge system canbe connected and if further mitigation effort

is needed, the system can be activated byinstalling an in-line duct fan (see Figure 4-7).

Subslab depressurization has proven tobe an effective technique for reducing radonconcentrations to acceptable levels, even inhomes with extremely high concentrations(Dudney 1988). This technique lowers thepressure around the foundation envelope,causing the soil gas to be routed into acollection system, avoiding the inside spacesand discharging to the outdoors. This systemcould be installed in two phases. The firstphase is the collection system located on thesoil side of the foundation, which should beinstalled during construction. The collectionsystem, which may consist of nothing morethan 4 inches of gravel beneath the slab floor,can be installed at little or no additional costin new construction. The second phase is thedischarge system, which could be installedlater if necessary.

A foundation with good subsurfacedrainage already has a collection system.The underslab gravel drainage layer can beused to collect soil gas. It should be at least 4inches thick, and of clean aggregate no lessthan 1/2 inch in diameter. Weep holesprovided through the footing or gravel bedextending beyond the foundation wall willhelp assure good air communication betweenthe foundation perimeter soil and theunderside of the slab. The gravel should becovered with a 6-mil polyethylene radon andmoisture retarder, which in turn could becovered with a 2-inch sand bed.

A 3- or 4-inch diameter PVC 12-inchsection of pipe should be inserted verticallyinto the subslab aggregate and capped at thetop. Stack pipes could also be installedhorizontally through below-grade walls tothe area beneath adjoining slabs. A singlestandpipe is adequate for typical house-sizefloors with a clean, coarse gravel layer. Ifnecessary, the standpipe can be uncappedand connected to a vent pipe. The standpipecan also be added by drilling a 4-inch holethrough the finished slab. The standpipeshould be positioned for easy routing to theroof through plumbing chases, interior walls,or closets. Note, however, that it is normallyless costly to complete the vent stack routingthrough the roof during construction than toinstall or complete the vent stack after thebuilding is finished. Connecting the ventpipe initially without the fan provides apassive depressurization system which maybe adequate in some cases and could bedesigned for easy modification to an active


Figure 4-7: Soil Gas Collection and Discharge Techniques

DISCHARGE FANLOCATED IN ATTIC

ROOF VENT FOR SOIL GAS DISCHARGE

RISER PIPE FROMAREA UNDER SLAB

STANDPIPES CAN BE CAPPED FOR FUTURE USE

CONCRETE SLABOVER POLYVAPOR BARRIER

GRAVEL DRAINAGE LAYER

SUCTION TAPCAST IN SLAB


system if necessary.A subslab depressurization system

requires the floor slab to be nearly airtight sothat collection efforts are not short-circuitedby drawing excessive room air down throughthe slab and into the system. Cracks, slabpenetrations, and control joints must besealed. Floor drains that discharge to thegravel beneath the slab should be avoided,but when used, should be fitted with amechanical trap capable of providing anairtight seal.

It is desirable to avoid dependence on acontinuously operating fan. Ideally, apassive depressurization system should beinstalled, radon levels tested and, ifnecessary, the system activated by adding afan. Active systems use quiet, in-line ductfans to draw gas from the soil. The fanshould be located in an accessible section ofthe stack so that any leaks from the positivepressure side of the fan are not in the livingspace. The fan should be oriented to preventaccumulation of condensed water in the fanhousing. The stack should be routed upthrough the building and extend 2 to 4 feetabove the roof. It can also be carried outthrough the band joist and up along theoutside of wall, to a point at or above the

eave line. The exhaust should be locatedaway from doors and windows to avoid re-entry of the soil gas into the above-gradespace.

A fan capable of maintaining 0.2 inch ofwater suction under installation conditions isadequate for serving subslab collectionsystems for most houses (Labs 1988). This isoften achieved with a 0.03 hp (25W), 160 cfmcentrifugal fan (maximum capacity) capableof drawing up to 1 inch of water beforestalling. Under field conditions of 0.2 inch ofwater, such a fan operates at about 80 cfm.

It is possible to test the suction of thesubslab system by drilling a small (1/4-inch)hole in an area of the slab remote from thecollector pipe or suction point, andmeasuring the suction through the hole. Asuction of 5 Pascals is considered satisfactory.The hole must be sealed after the test.

Active subslab depressurization doesraise some long-term concerns which at thistime are not fully understood. If the radonbarrier techniques are not fully utilized alongwith the subslab depressurization,considerable indoor air could be discharged,resulting in a larger than expected energypenalty. System durability is of concern,particularly motor-driven components. Thissystem is susceptible to owner interference.



11. Isolation joint: An isolation joint should beprovided at the slab edge to permitindependent movement without cracking.Where radon is a concern, a liquid sealantshould be poured into the joint over a foambacking rod.

12. Concrete slab: A minimum slab thicknessof 4 inches is recommended using concretewith a minimum compressive strength of 2500psi. Welded wire fabric placed 2 inches belowthe slab surface is recommended to controlshrinkage cracks. Generally, concrete slabsshould not rest on footings or ledges offoundation walls if possible to avoid crackingdue to settlement. If a slab is poured over animpermeable vapor retarder or insulation board,a concrete mixture with a low water/cementratio is recommended. An alternative techniqueis to pour the slab on a layer of sand ordrainage board above the vapor retarder tominimize cracking.

ISOLATION JOINT 11

4-IN. CONCRETE SLABWITH OPTIONALW.W. MESH 12


4.3 Slab-on-GradeConstruction Details

In this section, typical slab-on-gradefoundation details are illustrated anddescribed. Figure 4-9 shows exteriorinsulation applied to a grade beamfoundation. A grade beam supporting abrick veneer facade is shown in Figure 4-10with exterior insulation. Insulation appliedto the exterior of concrete and concretemasonry foundation walls is shown inFigures 4-11 and 4-12. Figure 4-13 illustratesinsulation placed beneath the slab perimeter.The inside insulation case is illustrated formasonry foundation walls in Figures 4-14

and 4-15. A foundation wall supporting abrick veneer facade is shown in Figure 4-16with interior insulation. Numbers that occurwithin boxes in each drawing refer to thenotes on page 75 that follow the drawings(see Figure 4-8).

The challenge at this stage of design is todevelop integrated solutions that address allkey considerations without significantlycomplicating the construction or increasingthe cost. There is no one set of perfectsolutions; recommended practices or detailsoften represent compromises and trade-offs.No particular approach is consideredsuperior in all cases. This section shows anddescribes a variety of reasonable alternatives.Individual circumstances will dictate finaldesign choices.


OPENING IN EVERY OTHERVERTICAL JOINT

FLASHING

GROUND SLOPES AWAY FROM WALL AT 5% 3

1/2-IN. ANCHOR BOLTSAT 6 FT. O.C. MAX. 4

RIGID INSULATION 6

INSULATED BLOCK SUPPORT FOR BRICK VENEER

4-IN. GRAVEL LAYER(OPTIONAL) 14


CONCRETE GRADE BEAM 10

BRICK VENEER

1-IN. AIRSPACE

RIGID INSULATION

PRESSURE-TREATED SILL PLATE (GASKET UNDER SILL PLATE) 1




VAPOR RETARDER 13

Figure 4-10: Slab-on-Grade with Brick Veneer (Exterior Insulation)

Figure 4-9: Slab-on-Grade with Integral Grade Beam (Exterior Insulation)

EXTERIOR SIDING

RIGID INSULATION USED AS SHEATHING EXTENDS DOWN TO COVER GRADE BEAM 6


TERMITE SHIELD

PROTECTION BOARDOR COATING 2



VAPOR RETARDER

INSULATON IN 2 x 4 WALL

4-IN. CONCRETE SLABWITH OPTIONAL W.W. MESH 12

VAPOR RETARDER 13

4-IN. GRAVEL LAYER (OPTIONAL) 14

CONCRETE GRADE BEAM 10

SILL ANCHORS AT6 FT. O. C. MAX. 4

RIGID INSULATION MAY EXTEND HORIZONTALLYINTO THE SOIL, SLOPINGAWAY FROM SLAB EDGE


8-IN. MIN.

Figure 4-9 illustrates a slab-on-grade foundation with anintegral grade beam. The rigidinsulation is placed verticallyon the exterior face of the gradebeam. Additional insulationmay be extended horizontallyaround the foundationperimeter.

Figure 4-10 illustrates a slab-on-grade foundation with anintegral grade beam. Thisdiffers from Figure 4-9 in thatthe above grade wall is woodframe with brick veneer. Therigid insulation is placedvertically on the exterior faceof the grade beam and extendsupward into the cavitybetween the wood frame walland the brick veneer.


Figure 4-12: Slab-on-Grade with Masonry Wall (Exterior Insulation)

1/2-IN. ANCHOR BOLTSAT 6 FT. O.C. MAX.EMBEDDED 15 IN. INTO FILLED CORES 5

RIGID INSULATIONOVER CONCRETEMASONRY WALL 6 8

EXTERIOR SIDING

SHEATHING


FLASHING COVERS TOP OF INSULATION




VAPOR RETARDER


ISOLATION JOINT 11


VAPOR RETARDER 13



CONCRETE FOOTING 10

8-IN.MIN.

Figure 4-11: Slab-on-Grade with Concrete Wall (Exterior Insulation)


RIGID INSULATION 6

CONCRETEFOUNDATION WALL 7

CONCRETE FOOTING 10

EXTERIOR SIDING

SHEATHING





VAPOR RETARDER


ISOLATION JOINT 11



VAPOR RETARDER 13



8-IN.MIN.

Figure 4-11 illustrates a slab-on-grade with a concretefoundation wall. Rigidinsulation is placed verticallyon the exterior face of thefoundation wall. The 2 x 6above-grade wood frame walloverhangs the insulation. Thefoundation wall is designed topermit vertical movement ofthe floor slab.

Figure 4-12 illustrates a slab-on-grade foundation with aconcrete masonry foundationwall. Rigid insulation isplaced vertically on theexterior face of the foundationwall. The top of the insulationis covered by flashing. Becausethe floor slab rests on the ledgeof the foundation wall, it isimportant to compact the soilbeneath the slab to minimizesettlement and cracking of theslab.


Figure 4-14: Slab-on-Grade with Masonry Wall (Insulation Under Slab)

Figure 4-13: Slab-on-Grade with Concrete Wall (Insulation Under Slab)


CONCRETEFOUNDATION WALL 7

CONCRETE FOOTING 10

EXTERIOR SIDING

SHEATHING





VAPOR RETARDER

RIGID INSULATION IN JOINT 11

4-IN. CONCRETE SLAB WITH OPTIONAL W.W. MESH 12


VAPOR RETARDER 13

RIGID INSULATION 15



8-IN.MIN.


EXTERIOR SIDING

SHEATHING



6-IN. CONCRETE BLOCKON 8-IN. CONCRETEMASONRY WALL 8



VAPOR RETARDER

RIGID INSULATION JOINT 11


VAPOR RETARDER 13

RIGID INSULATION 15



CONCRETE FOOTING 10

8-IN.MIN.

Figure 4-13 illustrates a slab-on-grade with a concretefoundation wall. Rigidinsulation is placedhorizontally under the slabperimeter and vertically in thejoint at the slab edge. Anoptional sand layer beneath theslab is shown. The foundationwall is designed to permitvertical movement of the floorslab.

Figure 4-14 illustrates a slab-on-grade with a concretemasonry foundation wall.Rigid insulation is placedhorizontally under the slabperimeter and vertically in thejoint at the slab edge. In orderto permit vertical movement ofthe floor slab, 6-inch wideconcrete blocks are used in thetop course. This approachutilizes a 2 x 6 above-gradewood frame wall.



6-IN. BLOCK SUPPORTFOR BRICK VENEER


RIGID INSULATION 15



CONCRETE FOOTING 10

BRICK VENEER

1-IN. AIRSPACE

SHEATHING




RIGID INSULATION IN JOINT 11


VAPOR RETARDER 13

OPENING IN EVERY OTHERVERTICAL JOINT

FLASHING


Figure 4-16: Slab-on-Grade with Brick Veneer (Insulation Under Slab)

Figure 4-15: Slab-on-Grade with Masonry Wall (Interior Insulation)


CONCRETEMASONRY WALL 8

EXTERIOR SIDING

SHEATHING





VAPOR RETARDER

RIGID INSULATION JOINT 11


VAPOR RETARDER 13


RIGID INSULATION 16


CONCRETE FOOTING 10

8-IN.MIN.

Figure 4-15 illustrates a slab-on-grade foundation with aconcrete masonry foundationwall. Rigid insulation isplaced vertically on the interiorface of the foundation wall andextends into the joint at theslab edge. Because the floorslab rests on the ledge of thefoundation wall, it isimportant to compact the soilbeneath the slab to minimizesettlement and cracking of theslab. This approach utilizes a2 x 4 above-grade wood framewall.

Figure 4-16 illustrates a slab-on-grade with a concretefoundation wall. The approachabove-grade wall systemconsists of a 2 x 4 wood framewall with brick veneer. Rigidinsulation is placedhorizontally under the slabperimeter and vertically in thejoint at the slab edge. Becausethe floor slab rests on the ledgeof the foundation wall, it isimportant the compact the soilbeneath the slab to minimizesettlement and cracking of theslab.


NOTES FOR ALL DETAILEDSLAB-ON-GRADE DRAWINGS(FIGURES 4-9 THROUGH 4-16)

1. Sill plate: The sill plate should be at least 8inches above grade and pressure-preservativetreated to resist decay.

2. Insulation protection: Exterior insulationmaterials should not be exposed above grade. Theabove-grade material should be covered by aprotective material — such as exterior grade plastic,fiberglass, galvanized metal or aluminum flashing, ora cementitious coating — extending at least 6 inchesbelow grade.

3. Surface drainage: The ground surface shouldslope downward at least 5 percent (6 inches) over thefirst 10 feet surrounding the foundation edge to directsurface runoff away from the building. Downspoutsand gutters should be used to collect roof drainageand direct it away from the foundation walls.

4. Anchor bolts for concrete walls: Anchor boltsshould be embedded in the top of concretefoundation walls. Most codes require bolts of 1/2-inch minimum diameter to be embedded at least 7inches into the wall. Generally, anchor bolts can beplaced at a maximum spacing of 6 feet and no furtherthan 1 foot from any corner.

5. Anchor bolts for masonry walls: Anchor boltsshould be embedded in the top of masonryfoundation walls. Most codes require bolts of 1/2-inch minimum diameter embedded at least 7 inchesinto the wall. In some locations, codes require boltsto be embedded 15 inches in masonry walls to resistuplift. To provide adequate anchorage in a masonrywall, bolts either must be embedded in a bond beamor the appropriate cores of the upper course of blockmust be filled with mortar. Anchor bolts can beplaced at a maximum spacing of 6 feet and no furtherthan 1 foot from any corner.

6. Exterior insulation materials: Acceptablematerials for exterior foundation insulation are: (1)extruded polystyrene boards (XEPS) under anycondition, (2) molded expanded polystyrene boards(MEPS) for vertical applications when porous backfilland adequate drainage are provided, and (3)fiberglass or polystyrene drainage boards wheninstalled with an appropriate drainage system.

7. Cast-in-place concrete wall: Concrete used inthe wall should have a minimum compressivestrength of 2500 psi with a 4- to 6-inch slump. Noadditional water should be added at the job site.Generally, where there are stable soils and lowseismic activity, no reinforcing is required.

8. Concrete/masonry wall: Generally, where thereare stable soils and in areas of low seismic activity,no reinforcing is required.

9. Crack control reinforcing in footing:Reinforcing bars placed 2 inches below the top of thefooting or 2 inches above the bottom of the gradebeam, running parallel to the wall, are recommendedwhere differential settlement is a potential problem.(Optional)

10. Concrete footings or grade beams: Concretefootings or grade beams should be designed todistribute the load to the soil and be placed beneaththe maximum frost penetration depth unless foundedon bedrock or proven non-frost-susceptible soil, orinsulated to prevent frost penetration. Concreteshould have a minimum compressive strength of2500 psi.

11. Isolation joint: An isolation joint should beprovided at the slab edge to permit independentmovement without cracking. Where radon is aconcern, a liquid sealant should be poured into thejoint over a foam backing rod.

12. Concrete slab: A minimum slab thickness of 4inches is recommended using concrete with aminimum compressive strength of 2500 psi. Weldedwire fabric placed 2 inches below the slab surface isrecommended to control shrinkage cracks.Generally, concrete slabs should not rest on footingsor ledges of foundation walls if possible to avoidcracking due to settlement. If a slab is poureddirectly over an impermeable vapor retarder orinsulation board, a concrete mixture with a low water/cement ratio is recommended. An alternativetechnique is to pour the slab on a layer of sand ordrainage board material above the vapor retarder tominimize cracking.

13. Vapor retarder: A 6-mil polyethylene vaporretarder should be placed beneath the slab to reducemoisture transmission and radon infiltration into thebuilding.

14. Gravel layer under slab: A 4-inch compactedgravel layer should be placed under the concretefloor slab for drainage unless local conditions haveproven this to be unnecessary. (Optional)

15. Insulation under the slab: Acceptable materialsfor underslab insulation are: (1) extruded polystyreneboards (XEPS) under any condition, (2) moldedexpanded polystyrene boards (MEPS) when thecompressive strength is sufficient and adequatedrainage is provided, and (3) insulating drainageboards with sufficient compressive strength.

16. Interior rigid insulation materials: Acceptablematerials for placement inside a foundation wallinclude (1) extruded polystyrene boards (XEPS) and(2) expanded polystyrene boards (MEPS).


4.4 Checklist for Design and Construction ofSlab-on-Grade Foundations


OVERALL SLAB CONSTRUCTION

General considerations. Slab floors require advance planning for plumbing andelectrical service. They generally minimize moisture and radon hazard but make detection oftermite intrusions especially difficult. Expansive soils require special measures.

____ ____ Elevate slab above existing grade____ ____ Provide minimum 4-inch-thick aggregate drainage layer under slab____ ____ Locate plumbing to be cast in slab____ ____ Locate electrical service to be cast in slab____ ____ Locate gas service to be cast in slab

SITEWORK







FOOTINGS

____ ____ Position bottom of footing at least 6 inches below frost depth aroundperimeter (frost wall at garage, slabs supporting roofs, other elementsattached to structure).


plan____ ____ Use keyway or steel dowels to anchor foundation walls____ ____ Dimension stepped footings according to local codes and good practice

(conform to masonry dimensions if applicable)____ ____ Provide through-joint flashing as a capillary break

STRUCTURAL

____ ____ Avoid ledge-supported slabs unless structurally reinforced____ ____ Place isolation joints at frost wall, columns, footings, fireplace foundations,

mechanical equipment pads, steps, sidewalks, garage and carportslabs, drains

____ ____ Check that partition load does not exceed 500 pounds per linear foot onunreinforced slab

____ ____ Call out depressed bottom of slab where top is depressed____ ____ Reinforce slab at depressions greater than 1-1/2 inch____ ____ Use wire chairs or precast pedestals to support WWF____ ____ Place sand layer over vapor retarder or insulation board____ ____ Compact fill under slab

Determine general concrete specifications:

____ ____ Minimum compressive strength after 28 days____ ____ Maximum water/cement ratio. Note: add no water at site____ ____ Allowable slump____ ____ Acceptable and unacceptable admixtures____ ____ Curing requirements (special hot, cold, dry conditions)____ ____ Dampening of subgrade prior to pour____ ____ Surface finish____ ____ Shrinkage control: WWF reinforcement or control joints____ ____ Key or dowelling for construction joints

SLAB-ON-GRADE FOUNDATION CHECKLIST (PAGE 2 OF 4)


THERMAL AND MOISTURE CONTROLS

General considerations. Heat loss rate is greatest at the exposed slab edge or frost wallabove grade, and at the floor perimeter. Continuity of insulation is difficult except forexterior placement. Horizontal exterior insulation reduces frost penetration depth.

____ ____ Confirm that insulation R-value meets local codes and/orrecommendations from this handbook

____ ____ Install insulation product suitable for in-ground use____ ____ Install infiltration sealing gasket under sole plate____ ____ Place vapor retarder under slab

DECAY AND TERMITE CONTROL MEASURES


____ ____ Reinforce slab____ ____ Remove all grade stakes, spreader sticks, wood embedded in concrete

during pour____ ____ Do not disturb treated soil prior to concreting____ ____ Avoid ducts beneath floor slab top surface____ ____ Specify pressure-treated wall sole plates and sleepers____ ____ Pressure-treat sill plates, rim joists, wood members in contact with

foundation walls and floors____ ____ Pressure-treat all outdoor weather-exposed wood members____ ____ Install dampproof membrane under sill plate (flashing or sill seal gasket)____ ____ Elevate sill plate minimum 8 inches above exterior grade____ ____ Elevate wood posts and framing supporting porches, stairs, decks, etc.,



clearance or provide proper flashing (for drainage and termiteinspection)

____ ____ Pitch solid surface porches, decks, patios for drainage (minimum 1/4 in/ft)____ ____ Detail slab porch and patios to prevent termite access to superstructure

(structural slab over inspectable crawl space)____ ____ Treat soil with termiticide, especially with insulated slab



RADON CONTROL MEASURES

General considerations. The potential for radon hazard is present in all buildings.Check state and local health agencies for need of protection. Strategies: (1) barriers; (2) airmanagement; (3) provisions to simplify retrofit. Since radon is a gas, its rate of entry throughthe foundation depends on suction due to stack effect and superstructure air leakage.

____ ____ Reinforce slab____ ____ Remove all grade stakes, spreader sticks, wood embedded in concrete

during pour____ ____ Form perimeter wall joint with trough, fill with pour-in sealant____ ____ Place vapor retarder under slab (optional sand layer)____ ____ Caulk joints around pipes and conduits____ ____ Place minimum 4-inch-thick layer of coarse, clean gravel under the slab____ ____ Separate outdoor intakes for combustion devices____ ____ Install air barrier wrap around superstructure____ ____ Seal around flues, chases, vent stacks, attic stairs


____ ____ Plans and specs____ ____ Bid package____ ____ Contractual arrangements (describe principals, describe the work by

referencing the blueprints and specs, state the start/completion dates,price, payment schedule, handling of change orders, handling ofdisputes, excavation allowance, and procedure for firing)

____ ____ Building permits


____ ____ After excavation and before concrete is poured for the footings____ ____ After the footings have been poured before foundation wall construction____ ____ After foundation construction and dampproofing before rough framing____ ____ After rough framing____ ____ After rough plumbing____ ____ After rough electrical____ ____ After insulation installation before drywall and backfilling in case of



Chapter 5—Worksheet for Determining Optimal Foundation Insulation

Worksheet for Selection ofOptimal Foundation Insulation

This worksheet will help you choose theoptimal foundation insulation location andamount for a new or existing residentialbuilding based on your specific buildingconstruction, climate, heating and coolingequipment, insulation cost, and othereconomic considerations. The energysavings of various foundation insulationconfigurations can be determined from thesame heating and cooling load data used todevelop the general recommendations inchapters 2, 3, and 4. However, here you mayinput your current local energy prices andactual insulation costs, and you may choosefrom three different economic decisioncriteria: (1) a 20-year minimum life cycle cost(suggested for retrofit); (2) a 30-yearminimum life cycle cost, as used in ASHRAE90.2P (ASHRAE 1989), the CABO ModelEnergy Code (CABO 1989), and to developthe general recommendations in chapter 2, 3,and 4 of this handbook; or (3) a second-yearpositive cash flow.

The major steps of the worksheet areshown schematically in Figure 5-1. Theformulas used as a basis for Worksheet 1 areshown in Figure 5-2. Step-by-stepinstructions guide you through the fill-in-the-blank worksheet. Most of the blanks may befilled with inputs you select from theaccompanying tables. Included in the tablesare representative insulation R-values andinstallation costs. However, optionalworksheets are provided to help youestimate your actual insulation installationcost (Worksheet 2), and to determineadditional R-values not included in the list oftypical values shown in Table 5-2 (Worksheet3). The worksheets and tables as well asaccompanying descriptions and instructionsappear in section 5.1. This is followed bysome examples of how to use the worksheetsin section 5.2.

Figure 5-1: Steps in Worksheet to Determine OptimalFoundation Insulation

DETERMINE HEATINGCLIMATE

IDENTIFY FOUNDATION CHARACTERISTICS

DETERMINE HEATING LOAD SAVINGS

DETERMINE HEATING ENERGY DOLLAR SAVINGS

STEP A:

STEP B:

STEP C:

STEP D:

STEP E:

STEP F:

STEP G:

STEP H:

DETERMINE COOLING CLIMATE

DETERMINE COOLING LOAD SAVINGS

DETERMINE COOLING ENERGY DOLLAR SAVINGS

DETERMINE NET DOLLAR SAVINGS

CHAPTER 5


cooling degree hours (CDH base 74OF), fromTable␣ 5-1. Table 5-2 provides the list offoundation types and insulationconfigurations covered by the worksheet.You can specify any reasonable effective R-value and installed insulation cost. Examplesof typical average installed costs for newconstruction in 1987 are provided in Table 5-2, which includes a markup for thesubcontractor and the builder. However, youmay choose to estimate your own foundationinsulation costs by using Worksheet 2. If adesired level of insulation is not provided inTable 5-2, you may use Worksheet 3 fordetermining the U-values needed to considerthis option in the optimization.

5.1 Descriptions andInstructions for Worksheets

THERMAL PERFORMANCE

Worksheet 1 helps you estimate theheating and cooling load changes resultingfrom the foundation insulation options youare considering. The first page of theworksheet addresses the heating seasonsavings while the second page addressescooling season savings. On each page youidentify your climate by entering the localheating degree days (HDD base 65OF) and

Figure 5-2: Formulas Used as a Basis for Worksheet 1

Heating Load Factor = HLFI + (HLFS x HDD)

Heating Load Savings = Heating Load Factor x UDELTA x HDD _________________________________________________________________________________

1,000,000

Heating Energy Dollar Savings = Heating Load Savings x Economic Scalar Ratio ____________________________________________________

HEEF x Duct Efficiency

x (Heating Energy Price Rate x Conversion Factor)

Cooling Load Factor = CLFI + (CLFS x CDH)

Cooling Load Savings = Cooling Load Factor x UDELTA x CDH _________________________________________________________________________________

1,000

Cooling Energy Dollar Savings = Cooling Load Savings x Economic Scalar Ratio ___________________________________________________

CEEF x Duct Efficiency

x (Cooling Energy Price Rate x Conversion Factor)

Net Dollar Savings = Heating Energy Dollar Savings + Cooling Energy Dollar Savings

- Installation Costs

Notes: 1. HLFI and HLFS are factors found in Table 5-3.2. CLFI and CLFS are factors found in Table 5-4.3. HDD are heating degree days found in Table 5-1.4. CDH are cooling degree hours found in Table 5-1.5. UDELTA is the difference in U-value between the uninsulated case and an

insulated case. UDELTA can be found in Table 5-2 or calculated usingWorksheet 3.

6. HEEF is the heating system efficiency and CEEF is the cooling systemefficiency (see Table 5-6).

7. Economic scalar ratio is found in Table 5-7.


ENERGY SAVINGS

Once the load changes are derived foreach case, the energy savings can beestimated. The selection of the present worthscalar ratios is where you define your desiredeconomic decision criteria. Table 5-7provides a variety of scalar ratios derivedusing three different economic decisioncriteria: second-year positive cash flow, 20-year life cycle cost, and 30-year life cycle cost.Also shown are seven different fuelescalation rates (0 to 6 percent) which includeinflation, and three mortgage rates: 10, 11,and 12 percent.

The scalar ratio is the ratio of the presentworth factor for energy savings divided bythe present worth factor of mortgagepayments for the added foundationinsulation cost. The present worth factor forthe mortgage payments adjusts for incometax savings and accounts for points paid atthe beginning of occupancy as a loanplacement fee. It is based on no additionaldown payment, 1 percent loan placement fee“points”, 10 percent after tax equivalentdiscount rate, and 30 percent marginalincome tax (state and federal combined). Thehigher the scalar ratio, the greater the presentworth value of the energy savings, whichleads to higher recommended insulationlevels. A simple way of thinking about thescalar ratio is that it is the maximumallowable simple payback to the homeownerof any foundation insulation cost.

NET DOLLAR SAVINGS

The last step in the worksheet derives thenet dollar savings of each foundationinsulation option. Installed costs arepresented in Table 5-2 or may be determinedusing Worksheet 2. The option with thehighest positive net savings value in step Hof Worksheet 1 is the most cost-effectiveoption.

VALIDATION OF WORKSHEET 1

The objective of this worksheet is to leadyou to the most cost-effective foundationinsulation level based on your specificeconomic and HVAC performancecharacteristics. This procedure has beenshown to reproduce the recommendedinsulation configuration tables in chapters 2,3, and 4 of this handbook. Over 200 caseswere run through this worksheet and the

results compared to more detailed computersimulations. The worksheet led to the exactsame recommended configuration over 80percent of the time. Most of the cases thatwere different resulted from the relativelysimilar net savings values from a number ofdifferent configurations.

INSTRUCTIONS FORWORKSHEET 1

Suggestion: Make photocopies of theworksheets, keep the originals for future jobs.

Step A. Select the foundation type andinsulation configuration from Table 5-2. Youmay choose more than one insulationconfiguration from Table 5-2 in order tocompare the results. For example, for theslab foundation type you can include thefollowing insulation configurations: 2 ftvertical exterior, 4 ft vertical exterior, and 2 ftvertical interior. Enter the installation cost foreach configuration on line 4. Some typicalvalues for new construction costs are shownin Table 5-2. These costs were nationalaverage values in 1987, but you must useWorksheet 2 to obtain current costs.

Step B. Determine heating degree daysbase 65OF (HDD) for your climate from Table5-1 and enter on line 5.

Step C. For determining the heating loadsavings, enter coefficients (HLFI, HLFS) fromTable 5-3 for the appropriate climate andfoundation system on lines 6 and 7. Multiplyline 7 (HLFS) by line 5 (HDD) and enter theresult on line 8. Add lines 6 and 8 and enterthe results on line 9 (this is the heating loadfactor). Enter UDELTA from Table 5-2 (orWorksheet 3) on line 10. The heating loadsavings of each foundation option aredetermined by multiplying UDELTA from line10 by the heating load factor on line 9, thenmultiplying that result by HDD from line 5and finally dividing by 1,000,000 for eachoption.

Step D. Suggested values for the heatingequipment efficiency (HEEF) are listed inTable 5-6. The data base on which thisworksheet is based uses 0.9 for the HVACduct efficiency (line 15) for unconditionedspaces like attics and crawl spaces. Ductefficiencies can be much lower. ASHRAE90.2P used a heating duct efficiency of 0.75when ducts are in unconditioned spaces.When ducts are located within the


CASE 1 CASE 2 CASE 3

STEP A: IDENTIFY FOUNDATION CHARACTERISTICS

1. Enter foundation type (basement, crawl space, or slab) _____________ _____________ _____________

2. Enter insulation configuration from Table 5-2 _____________ _____________ _____________

3. Enter nominal R-value from Table 5-2 _____________ _____________ _____________

4. Enter installation cost from Table 5-2 or use Worksheet 2[units: $/lin ft or $/sq ft]* _____________ _____________ ____________

STEP B: DETERMINE HEATING CLIMATE

5. Enter heating degree days (HDD) from Table 5-1 _____________ _____________ _____________

STEP C: DETERMINE HEATING LOAD SAVINGS

6. Enter HLFI from Table 5-3 _____________ _____________ _____________

7. Enter HLFS from Table 5-3 _____________ _____________ _____________

8. Multiply line 7 (HLFS) by line 5 (HDD) _____________ _____________ _____________

9. Add lines 6 and 8 [units: Btu/(HDD x UDELTA)] _____________ _____________ _____________

10. Enter UDELTA from Table 5-2 (or Worksheet 3) _____________ _____________ _____________

11. Multiply line 9 by line 10 _____________ _____________ _____________

12. Multiply line 11 by line 5 (HDD) _____________ _____________ _____________

13. Divide line 12 by 1,000,000 [units: MBtu/lin ft or sq ft]* _____________ _____________ _____________

STEP D: DETERMINE HEATING ENERGY DOLLAR SAVINGS

14. Enter heating system efficiency from Table 5-6 (HEEF) _____________ _____________ _____________

15. Multiply line 14 by 0.9 (duct efficiency) _____________ _____________ _____________ (see instructions for alternative duct efficiency numbers)

16. Divide line 13 (heating load savings) by line 15 _____________ _____________ _____________

17. Enter heating energy price rate and multiply by conversion factor:

A. Electricity: __________$ per kWh X 293 = _____________ _____________ _____________

B. Natural gas: __________$ per therm X 10 = _____________ _____________ _____________

C. Fuel oil: __________$ per gallon X 7.2 = _____________ _____________ _____________

D. Propane: __________$ per gallon X 10.9 = _____________ _____________ _____________


19. Enter the economic scalar ratio from Table 5-7 _____________ _____________ _____________

20. Multiply line 18 by line 19 [units: $/lin ft or sq ft]* _____________ _____________ _____________

(NOTE: If cooling energy savings are not to be included in the calculation, go directly to STEP H.)

* If the configuration utilizes perimeter insulation then all units are expressed per lineal foot. If the configuration utilizes ceilinginsulation then all units are expressed per square foot.

Worksheet 1: Selection of Optimal Foundation Insulation (Page 1 of 2)



STEP E: DETERMINE COOLING CLIMATE

21. Enter cooling degree hours (CDH) from Table 5-1 _____________ _____________ _____________

STEP F: DETERMINE COOLING LOAD SAVINGS

22. Enter CLFI from Table 5-4 _____________ _____________ _____________

23. Enter CLFS from Table 5-4 _____________ _____________ _____________

24. Multiply line 23 (CLFS) by line 21 (CDH) _____________ _____________ _____________

25. Add lines 22 and 24 [units: Btu/(CDH x UDELTA

)] _____________ _____________ .._____________

26. Enter UDELTA

from line 10 ( Table 5-2 or Worksheet 3) _____________ _____________ .._____________

27. Multiply line 26 (UDELTA

) by line 25 (CLF) _____________ _____________ _____________

28. Multiply line 27 by line 21 (CDH) _____________ _____________ _____________

29. Divide line 28 by 1,000 [units: KBtu/lin ft or sq ft]* _____________ _____________ ____________

STEP G: DETERMINE COOLING ENERGY DOLLAR SAVINGS

30. Enter cooling system efficiency from Table 5-6 (CEEF) _____________ _____________ _____________

31. Multiply line 30 by 0.9 (duct efficiency) _____________ _____________ _____________

32. Divide line 29 (cooling load savings) by line 31 _____________ _____________ _____________

33. Enter cooling energy electric rate (i.e., $ 0.078 per kWh) _____________ _____________ _____________




STEP H: DETERMINE NET DOLLAR SAVINGS

37. Add line 20 (heating) and line 36 (cooling) _____________ _____________ _____________

38. Subtract line 4 (costs) from line 37 (savings)[units: $/lin ft or sq ft]* _____________ _____________ _____________


Worksheet 1: Selection of Optimal Foundation Insulation (Page 2 of 2)


conditioned space, use a value between 0.9and 1.0. Line 17 is the current year's heatingenergy price. Multiplying the energy pricerate by the conversion factors shown on line17 expresses the result in $/MBtu.

The economic scalar ratio is used todetermine the present worth of thefoundation insulation heating energysavings. Table 5-7 provides a variety ofscalar ratios calculated with differentmortgage rates, fuel escalation rates, andthree different economic decision criteria: (1)second-year positive cash flow, (2) 20-yearminimum life cycle cost analysis, and (3) 30-year minimum life cycle cost analysis. Thesecond-year positive cash flow criteriarequires that after the second year theadditional mortgage payment for thefoundation insulation be less than theresulting annual energy savings. TheBuilding Foundation Design Handbook (Labs etal. 1988), ASHRAE Standard 90.2P (ASHRAE1989), and the Model Energy Code (CABO1989) are all based on a scalar ratio of about18. To be consistent with these codes andstandards, use 18 in line 19. The result online 20 is the heating energy dollar savings.

Step E. Determine cooling degree hoursbase 74OF (CDH) for your climate from Table5-1 and enter on line 21.

Step F. For determining the cooling loadsavings, enter coefficients (CLF

I, CLF

S) from

Table 5-4 for the appropriate climate andfoundation system on lines 22 and 23.Multiply line 23 (CLF

S) by line 21 (CDH) and

enter the result on line 24. Add lines 22 and24 and enter the results on line 25 (this is thecooling load factor). Enter U

DELTA from Table

5-2 (or Worksheet 3) on line 26. The coolingload savings of each foundation option aredetermined by multiplying U

DELTA from line

26 by the cooling load factor on line 25, thenmultiplying that result by CDH from line 21and finally dividing by 1,000 for each option.

Step G. Suggested values for the coolingequipment efficiency (CEEF) are shown inTable 5-6. Line 31 is the HVAC ductefficiency while providing cooling. TheBuilding Foundation Design Handbook assumes0.9 for cooling duct efficiency. ASHRAE90.2p uses 0.8 for cooling duct efficiency,when ducts are in unconditioned spaces.Line 33 is the current year's cooling energy

INSTRUCTIONS FORWORKSHEET 1 (CONTINUED)

price (consult your local electric utility forprices). The value to be entered in line 33must be in dollars per kWh. Line 35 is thescalar ratio used to estimate the presentworth of the cooling energy savings resultingfrom foundation insulation. Table 5-7provides a variety of scalar ratios based ondifferent economic criteria, mortgage rates,and real fuel escalation rates. To beconsistent with various codes and standardslisted in Step D, use a scalar ratio of 18 in line35. The result on line 36 is the cooling energydollar savings.

Step H. The option with the largestpositive value in line 38 is the most cost-effective option. This step subtracts the firstcost of each option (line 4) from thecorresponding present worth value of theenergy savings. If all the net savings valuesin line 38 are negative, this indicates thatnone of the cases meet your cost-effectivenesscriteria. Select a set of options that havelower installed costs and repeat theworksheet. If still none exist, foundationinsulation may not be a good investment forthis project.


Worksheet 2: Optional Method for Estimating Foundation Insulation Installation Cost

CASE 1 CASE 2 CASE 3STEP A: DETERMINE MATERIAL COST

1. Enter the total material cost of insulation _____________ _____________ _____________

2. Enter the total material cost of fasteners _____________ _____________ _____________

3. Enter the cost of protective covering or required flamespread protection _____________ _____________ _____________

4. Add lines 1, 2, and 3 to determine the total material cost _____________ _____________ _____________

STEP B: DETERMINE LABOR COST

5. Enter site preparation cost _____________ _____________ _____________

6. Enter installation cost for insulation _____________ _____________ _____________

7. Enter installation cost for any framing or furring _____________ _____________ _____________

8. Enter installation cost for any protective covering _____________ _____________ _____________

9. Add lines 5, 6, 7, and 8 to determine total labor cost _____________ _____________ _____________

STEP C: DETERMINE TOTAL INSTALLED COST

10. Add lines 4 and 9 _____________ _____________ _____________

11. Multiply line 10 by the subcontractor markup(example: 1.3) _____________ _____________ _____________

12. Multiply line 11 by the general contractor markup(example: 1.3) _____________ _____________ _____________

13. Divide line 12 by the foundation perimeter lengthin feet _____________ _____________ _____________


Step A. Material costs should be for theentire job. Line 1 represents the materialcosts for the entire area to be covered. Line 2includes the insulation attachment materials;examples are fasteners for exterior systemsand framing for interior systems. Line 3includes the above-grade protection neededfor exterior insulation or flame spreadprotection for interior applications. If thecovering provides other amenities such asaesthetics (basement finishing neededanyway) then this cost should be zero.

Step B. Line 5 includes surfacepreparation that may be needed such ascleaning prior to liquid adhesive application.In retrofit installations the cost of excavationfor exterior systems and interior wall fixture

relocation for interior systems should beentered. Lines 6 and 7 cover total labor costof attaching the insulation. Line 8 includesthe labor for applying either the exteriorabove-grade covering or flame spreadprotection covering on the interior if doneonly to meet safety standards.

Step C. The total installed cost mayinclude subcontractor markup (line 11) andbuilder markup (line 12). These markupsaccount for indirect charges, overhead, andprofit. The costs for new constructionfoundation insulation in Table 5-2 include 30percent for both markups. For insulationretrofits, the builder markup should be 1.0.For homeowner retrofit the subcontractormarkup could also be 1.0. Line 13 convertsthe total cost into dollars per foundationperimeter foot, for use in Steps A and H ofWorksheet 1 for selection of optimalfoundation insulation.



Step A. The U-value of only theinsulation layer for foundation walls can becalculated by assuming parallel heat flowpaths through areas with different thermalresistances. Lines 1a through 1e are fractionsof the total area transverse to heat flowrepresenting the component materials of thewall system. For stud walls 16 inches oncenter, the fraction of framing is usuallyassumed to be approximately 0.15; for studs24 inches on center, it is approximately 0.12.Lines 2a through 2e are the R-values ofmaterials contained in the insulation layer.For example, an insulated stud wall will havewood and mineral batts.

Step B. RBASE

must be selected fromTable 5-5. It represents the system that wasmodeled and cannot be varied in thisworksheet. If the fasteners are to be ignoredfor board insulations as was done in Table 5-2, the nominal R-value can be added to R

BASEto obtain R

EFF. Insert R

EFF in line 6.

Step C. Use Table 5-5 to obtain theeffective R-value of the uninsulatedfoundation construction (R

BASE) and the

effective R-value of the adjacent soil (RSOIL

).These are not actual R-values, rather they arevalues that produce the best representation ofthe annual heating and cooling load savingsdata base on which this worksheet is based.These values should not be varied from thoseshown for each system in Table 5-5. Choosethe set of values listed for the foundationsystem options you would like to consider,then follow the calculation procedure onlines 9 and 10 to find U

BASE. This is the U-

value of the uninsulated case.

Step D. Add REFF

from line 6 to RSOIL

fromline 8 and enter the result on line 11. Followthe calculation procedure on line 12 to findU

TOTAL. This is the U-value of the insulated

case.

Step E. The difference in U-value foreach insulation level is determined bysubtracting U

TOTAL (line 12) from U

BASE (line

10) for each option.

Effective R-value (REFF

) = RBASE

+ 1 _______________________________________________________________

(Area1 / R

1 + Area

2 / R

2 + ...)

UBASE

= 1 ____________________________

RBASE

+ RSOIL

UTOTAL

= 1 _________________________

REFF

+ RSOIL

UDELTA

= UBASE

- UTOTAL

Notes: 1. RBASE

and RSOIL

are found in Table 5-5.2. Area

1 is the fraction of the total area covered by material 1 (i.e. material 1

may be insulation covering 90% of the wall while material 2 may bewood framing covering 10% of the wall)

3. R1 and R

2 represent the R-values of material 1 and material 2

4. REFF

, UBASE

, UTOTAL

, and UDELTA

are all defined in the instructions forworksheet 3 above

Figure 5-3: Formulas Used as a Basis for Worksheet 3


Worksheet 3: Optional Method for Determining UDELTA

CASE 1 CASE 2 CASE 3STEP A: CALCULATE THE U-VALUEOF INSULATION ASSEMBLY

1. Enter the fraction of the total area covered by each component

a. Component 1 (example: insulation) _____________ _____________ _____________

b. Component 2 (example: framing) _____________ _____________ _____________

c. Component 3 _____________ _____________ _____________

d. Component 4 _____________ _____________ _____________

e. Component 5 _____________ _____________ _____________

2. Divide the fractional values in line 1 by the corresponding R-values

a. Line 1a divided by R-value for component 1 _____________ _____________ _____________

b. Line 1b divided by R-value for component 2 _____________ _____________ _____________

c. Line 1c divided by R-value for component 3 _____________ _____________ _____________

d. Line 1d divided by R-value for component 4 _____________ _____________ _____________

e. Line 1e divided by R-value for component 5 _____________ _____________ _____________

3. Add the results of line 2 to determine the overall U-value

(2a + 2b + 2c + ...) _____________ _____________ _____________

STEP B: CALCULATE THE EFFECTIVE R-VALUE (REFF

)

4. Enter the appropriate RBASE

from Table 5-5 _____________ _____________ _____________

5. Divide 1 by line 3 _____________ _____________ _____________

6. Add lines 4 and 5 to determine REFF

_____________ _____________ _____________

STEP C: DETERMINE THE U-VALUE OF UNINSULATED CASE (UBASE

)

7. Enter RBASE

from Table 5-5 _____________ _____________ _____________

8. Enter RSOIL

from Table 5-5 _____________ _____________ _____________

9. Add lines 7 and 8 _____________ _____________ _____________

10. Divide 1 by line 9 [units: Btu/OF x ft2 x h] _____________ _____________ _____________

STEP D: DETERMINE THE U-VALUE OF INSULATED CASE (UTOTAL

)

11. Add line 6 (REFF

) and line 8 (RSOIL

) _____________ _____________ _____________


STEP E: DETERMINE U-VALUE DIFFERENCE (UDELTA

)

13. Subtract line 12 from line 10 [units: Btu/OF x ft2 x h] _____________ _____________ _____________


IndianaEvansville 14947 4260Ft. Wayne 7990 6320Indianapolis 9091 5650South Bend 6311 6377

IowaDes Moines 9512 6554Sioux City 10581 6947

KansasTopeka 16433 5319Wichita 19757 4787

KentuckyLexington 9472 4814Louisville 14868 4525

LouisianaBaton Rouge 24267 1673Lake Charles 24628 1579New Orleans 23546 1490Shreveport 26043 2269

MaineBangor 2234 7947Portland 2796 7501

MarylandBaltimore 10688 4706

MassachusettsBoston 5413 5593

MichiganDetroit 6519 6563Flint 4216 7068Grand Rapids 5813 6927Lansing 4938 6987

MinnesotaDuluth 1672 9901Minneapolis 6344 8007

MississippiJackson 23321 2389

MissouriKansas City 18818 5283Springfield 13853 4660St. Louis 16302 4938

MontanaBillings 6991 7212Great Falls 4498 7766

Table 5-1: Weather Data for Selected Cities (page 1 of 2)

AlabamaBirmingham 19497 2943Mobile 20047 169Montgomery 23355 2277

ArizonaPhoenix 52408 1442Tucson 38743 1734

ArkansasFort Smith 22474 3477Little Rock 22467 3152

CaliforniaBakersfield 27919 2128Fresno 21311 2647Los Angeles 2416 1595Sacramento 14026 2772San Diego 2514 1284San Francisco 843 3161

ColoradoColorado Springs 6089 6346Denver 8586 6014

ConnecticutHartford 5151 6174

District of ColumbiaWashington, D.C. 12121 5004

FloridaJacksonville 25200 1402Miami 32951 199Orlando 25072 656Tallahassee 18051 1652Tampa 26167 739Palm Beach 32531 262

GeorgiaAtlanta 15710 3021Augusta 20921 2563Macon 22388 2279Savannah 19953 1921

IdahoBoise 9804 5802

IllinoisChicago 6665 6455Springfield 12117 5654

Location CDH1 HDD2 Location CDH1 HDD2

1. Cooling degree hours - base 74 degrees Fahrenheit2. Heating degree days - base 65 degrees Fahrenheit


NebraskaOmaha 12448 6194

NevadaLas Vegas 44433 2532Reno 9403 6030

New MexicoAlbuquerque 15538 4414

New YorkAlbany 5461 6927Binghamton 2304 7344Buffalo 4284 6798New York City 8337 4922Rochester 5224 6713Syracuse 5274 6787

North CarolinaCharlotte 15940 3342Greensboro 12261 3874Raleigh 13851 3342Winston-Salem 11673 3679

North DakotaBismarck 6861 9075Grand Forks 4329 9881

OhioCanton 5041 6241Cincinnati 10178 4950Cleveland 6834 6178Columbus 9341 5447Dayton 8401 5255Toledo 6209 6570Youngstown 4734 6560

OklahomaTulsa 23642 3731

OregonEugene 4436 4799Medford 9500 4798Portland 2711 4691Salem 4443 4974

PennsylvaniaHarrisburg 8091 5335Philadelphia 9303 4947Pittsburgh 5024 5950Scranton 4219 6114

Rhode IslandProvidence 4359 5908

South CarolinaCharleston 16473 2147Columbia 21060 2629

South DakotaSioux Falls 7872 7885

TennesseeChattanooga 16361 3583Knoxville 14641 3658Memphis 21614 3207

TexasAmarillo 16968 4231Austin 32314 1760Brownsville 34029 609Corpus Chris 32684 945Dallas-Ft. Worth 34425 2301El Paso 28602 2664Houston 47650 1549Laredo 48983 926Lubbock 19974 3516Midland 26098 2658Nashville 17728 3756San Antonio 31614 1606Waco 31843 2126Wichita Falls 29921 3011

UtahSalt Lake City 12874 5802

VermontBurlington 3163 7953

VirginiaNorfolk 12766 3446Richmond 13546 3960Roanoke 10576 4315

WashingtonSeattle 1222 4681Spokane 5567 6882

WisconsinGreen Bay 3129 8143La Crosse 5738 7540Madison 6164 7642Milwaukee 4565 7326

West VirginiaCharleston 9486 4697Huntington 10419 4676

WyomingCasper 6723 7642

Table 5-1: Weather Data for Selected Cities (page 2 of 2)

Location CDH1 HDD2Location CDH1 HDD2

1. Cooling degree hours - base 74 degrees Fahrenheit2. Heating degree days - base 65 degrees Fahrenheit


Table 5-2: Insulation R-Values and Costs for Conditioned Basements (page 1 of 4)


INSTALLATIONCOST($ PER LF)

EXTERIOR: HALF WALL

EXTERIOR: FULL WALL

INTERIOR: FULL WALL

WOOD: FULL WALL



8 FT INTERIOR

WITHOUT DRYWALL

8 FT EXTERIOR

4 FT EXTERIOR

8 FT WOOD

4.04

4.44

5.32

6.54

7.52

8.47

6.2

7.01

8.77

10.87

12.71

14.55

18.35

8.52*

9.19*

9.87*

15.78*

B: Concrete Walls with Interior Insulation (Costs do not include interior finish material)

INTERIOR: FULL WALL 8 FT INTERIOR

WITH DRYWALL

C: Concrete Walls with Interior Insulation (Costs include sheetrock on interior wall)

4.72

5.76

6.48

10.24

12.32

13.36

12.56

16.32

NOMINAL R-VALUE

EFFECTIVE R-VALUE

4

5

8

10

12

15

4

5

8

10

12

15

20

6

8

11

19

6

8

11

19

11

13

19

30

5

6

9

11

13

16

5

6

9

11

13

16

21

5.23

6.83

10.7

18

5.7

7.4

11.26

18.56

11.8

13.5

18.5

27.9

* Costs include $6.08/ft for drywall covering that is not necessarily required.

U-DELTA

0.312

0.335

0.377

0.394

0.405

0.418

0.210

0.229

0.265

0.279

0.290

0.301

0.313

0.215

0.241

0.277

0.307

0.224

0.248

0.281

0.308

0.085

0.091

0.103

0.116


Table 5-2: Insulation R-Values and Costs for Unconditioned Basements (page 2 of 4)



EXTERIOR: HALF WALL

EXTERIOR: FULL WALL

INTERIOR: FULL WALL

WOOD: FULL WALL



8 FT INTERIOR

WITHOUT DRYWALL

8 FT EXTERIOR

4 FT EXTERIOR

8 FT WOOD

4.04

4.44

5.32

6.54

7.52

8.47

6.2

7.01

8.77

10.87

12.71

14.55

18.35

8.52*

9.19*

9.87*

15.78*

B: Concrete Walls with Interior Insulation (Costs do not include interior finish material)

INST. COST($ PER SF)

CEILINGE: Concrete or Masonry Foundation Walls with Ceiling Insulation

WOOD CEILING 0.34

0.41

0.52

0.86

INTERIOR: FULL WALL 8 FT INTERIOR

WITH DRYWALL

C: Concrete Walls with Interior Insulation (Costs include sheetrock on interior wall)

4.72

5.76

6.48

10.24

12.32

13.36

12.56

16.32

NOMINAL R-VALUE

EFFECTIVE R-VALUE

4

5

8

10

12

15

4

5

8

10

12

15

20

6

8

11

19

6

8

11

19

11

13

19

30

11

13

19

30

5

6

9

11

13

16

5

6

9

11

13

16

21

5.23

6.83

10.7

18

5.7

7.4

11.26

18.56

11.8

13.5

18.5

27.9

13

14

19

27.3

* Costs include $6.08/ft for drywall covering that is not necessarily required.

U-DELTA

0.221

0.241

0.277

0.292

0.302

0.314

0.116

0.129

0.156

0.168

0.176

0.186

0.197

0.119

0.138

0.166

0.191

0.126

0.144

0.169

0.192

0.315

0.326

0.346

0.364

0.092

0.096

0.112

0.126


Table 5-2: Insulation R-Values and Costs for Crawl Spaces (page 3 of 4)





2 FT INTERIOR

2 FT EXTERIOR

2 FT WOOD

2.00

2.97

1.32**

1.48**

1.76**

2.32**



D: Vented Crawl Space - Concrete or Masonry Foundation Walls with Ceiling Insulation

WOOD CEILING 0.34

0.41

0.52

0.86

1.15

2.12

1.92

2.13

2.57

NOMINAL R-VALUE

EFFECTIVE R-VALUE

5

10

5

10

11

13

19

11

13

19

30

11

13

19

30

6

11

6

11

12

14

20

11.8

13.5

18.5

27.9

13

14

19

27.3

EXTERIOR VERTICAL

INTERIOR VERTICAL

WITHIN WOOD WALL

CEILING

** Costs include fire protective covering on the interior face.

U-DELTA

0.307

0.363

0.307

0.363

0.369

0.379

0.397

0.145

0.153

0.169

0.184

0.131

0.137

0.156

0.172


Table 5-2: Insulation R-Values and Costs for Slab-on-Grade Foundations (page 4 of 4)




C: Concrete Walls with Interior Insulation Placed Horizontally Under Slab Perimeter

2 FT INTERIORVERTICAL/R-5 GAP

2 FT EXTERIORVERTICAL

2 FT HORIZONTALINTERIOR/R-5 GAP

2.04

2.252.64

3.504.02

4.58

1.652.80


D: Concrete Foundation Walls with Exterior Insulation Extending Outward Horizontally

2 FT HORIZONTAL EXTERIOR

3.53

5.70

1.30

2.19

NOMINAL R-VALUE

EFFECTIVE R-VALUE

4

58

1011

14

510

5

10

5

10

56

9

1112

15

6

11

6

11

6

11

EXTERIOR VERTICAL: 2ft

INTERIOR VERTICAL

INTERIOR HORIZONTAL

EXTERIOR HORIZONTAL

EXTERIOR VERTICAL: 4ft4 FT EXTERIORVERTICAL

45

810

12

1520

56

911

13

1621

3.133.53

4.415.70

6.66

7.699.68

2 FT INTERIORVERTICAL/R-5 GAP

5

10

1520

6

11

1621

2.59

4.40

6.238.06

4 FT HORIZONTALINTERIOR/R-5 GAP

5

106

11

2.69

4.52

4 FT HORIZONTAL EXTERIOR

5

10

6

11

4.53

7.90

U-DELTA

0.2840.307

0.347

0.3630.369

0.383

0.307

0.363

0.307

0.363

0.307

0.363

0.2840.307

0.3470.363

0.374

0.3860.400

0.307

0.363

0.3860.400

0.307

0.363

0.307

0.363


FOUNDATION SYSTEM CLIMATE

MORE THAN LESS THAN2500 HDD 2500 HDD

HLFI

HLFS

HLFI

HLFS

Slab2 ft vertical exterior 19.38 0 -4.40399 0.011702 ft vertical interior/R-5 gap 18.77 0 -4.14849 0.009962 ft horizontal interior/R-5 gap 19.42 0 -3.95460 0.009902 ft horizontal exterior 23.98 0 -5.21022 0.011544 ft horizontal exterior 25.34 0 -6.08104 0.012724 ft fdn exterior 24.30 0 -6.13994 0.015714 ft fdn interior/R-5 gap 24.20 0 -6.13994 0.015714 ft horizontal interior/R-5 gap 25.26 0 -6.33494 0.01381

Unvented Crawl Space2 ft exterior 19.06 0 2.56965 0.009012 ft interior 19.34 0 4.07627 0.008612 ft wood 17.40 0 -1.54462 0.00946

Vented Crawl Spaceceiling 21.435 0 21.435 0

Deep Basement (Conditioned)4 ft exterior 80.40 0 -5.63157 0.054308 ft exterior or 8 ft interior 155.06 0 -16.53665 0.098958 ft wood 186.07 0 -24.93757 0.11622

Deep Basement (Unconditioned)4 ft exterior 25.07 0 0.39093 0.012258 ft exterior or 8 ft interior 59.10 0 -6.14049 0.027588 ft wood 33.34 0 -0.82326 0.01519ceiling 14.81 0 -17.44417 0.01866

Table 5-3: Heating Load Factor Coefficients (HLFI and HLF

S)


FOUNDATION SYSTEM CLIMATE

MORE THAN15000 CDH AND

LESS THAN LESS THAN MORE THAN15000 CDH 30000 CDH 30000 CDH

CLFI

CLFS

CLFI

CLFS

CLFI

CLFS

Slab2 ft vertical exterior -1.89761 0.00015 1.02787 -0.00005 -1.93544 0.000052 ft vertical interior/R-5 gap -2.45376 0.00017 0.31361 -0.00003 -1.78118 0.000042 ft horiz. interior/R-5 gap -3.02223 0.00019 -0.33245 -0.00001 -1.89340 0.000054 ft vertical exterior -3.18708 0.00024 1.25057 -0.00007 -2.81314 0.000074 ft vertical interior/R-5 gap -2.43021 0.00016 0.31361 -0.00003 -1.78118 0.000044 ft horiz. interior/R-5 gap -5.58028 0.00033 -1.97537 0.00002 -3.32060 0.00007

Unvented Crawl Space2 ft exterior -1.43093 0.00012 1.07080 -0.00005 -1.92333 0.000052 ft interior -2.37578 0.00017 -1.23231 0.00003 -1.23231 0.000032 ft wood -2.16409 0.00016 1.42995 -0.00007 -2.50404 0.00006

Vented Crawl Spaceceiling -1.78237 0.00010 -1.07055 0.000003 -1.16166 0.00003

Deep Basement(Conditioned)

4 ft exterior 0.20910 0.00006 2.51623 -0.00008 -3.04576 0.000108 ft exterior or interior -0.09706 0.00010 4.73889 -0.00018 -6.98257 0.000208 ft wood -0.25473 0.00009 4.93520 -0.00021 -8.92914 0.00025

Deep Basement(Unconditioned)

4 ft exterior -3.45221 0.00022 0.70912 -0.00005 -3.10899 0.000088 ft exterior or interior -10.68317 0.00058 -1.34275 -0.00006 -8.91748 0.000218 ft wood -6.64161 0.00033 -0.73835 -0.00005 -6.25373 0.00015ceiling -3.84203 0.00020 -1.53760 0.00002 -2.11852 0.00005

Table 5-4: Cooling Load Factor Coefficients (CLFI and CLF

S)


Table 5-5: Initial Effective R-values for Uninsulated Foundation Systemand Adjacent Soil

Table 5-6: Heating and Cooling Equipment Seasonal Efficiencies1

LOW MEDIUM HIGH VERY HIGH

HEEFgas furnace 0.50 0.65 0.80 0.90oil furnace 0.50 0.65 0.80 0.90heat pump (HSCOP) 1.6 1.9 2.2 2.5electric furnace 1.0 1.0 1.0 1.0electric baseboard 1.0 1.0 1.0 1.0

CEEFheat pump (SEER) 7.25 8.75 10.25 11.75air conditioner (SEER) 6.0 8.0 10.0 12.0

1. Does not include duct losses

FOUNDATION SYSTEM RBASE

RSOIL

Slab2 ft vertical exterior 1.0 1.252 ft vertical interior/R-5 gap 1.0 1.252 ft horizontal interior/R-5 gap 1.0 1.252 ft horizontal exterior 1.0 1.254 ft horizontal exterior 1.0 1.254 ft vertical exterior 1.0 1.254 ft vertical interior/R-5 gap 1.0 1.254 ft horizontal interior/R-5 gap 1.0 1.25

Unvented Crawl Space2 ft exterior 1.0 1.252 ft interior 1.0 1.252 ft wood 2.5 2.1

Vented Crawl Spaceceiling 4.8 0

Deep Basement (Conditioned)4 ft exterior 1.0 1.18 ft exterior or 8 ft interior 1.0 1.88 ft wood 2.5 4.3

Deep Basement (Unconditioned)4 ft exterior 1.0 1.78 ft exterior or 8 ft interior 1.0 3.28 ft wood 2.5 0ceiling 4.8 1.4


Table 5-7: Scalar Ratios for Various Economic Criteria

1. Based on 10% real after tax discount rate2. Scalar ratio represents the maximum number of years allowed to have the energy savings resulting from the insulation

pay for financing the first cost of installing the insulation.3. This includes inflation.

SCALAR RATIO2

FUEL 2 YR 20 YR 30 YRMORTGAGE ESCALATION3 CROSS LIFE LIFE(PERCENT) (PERCENT) OVER CYCLE1 CYCLE1

10 0 13.25 10.07 11.6910 1 13.51 10.88 12.8410 2 13.78 11.75 14.1610 3 14.05 12.73 15.7010 4 14.31 13.83 17.4810 5 14.58 15.05 19.5810 6 14.84 16.41 22.0311 0 12.28 9.52 10.8411 1 12.53 10.28 11.9111 2 12.78 11.11 13.1411 3 13.02 12.06 14.5611 4 13.27 13.08 16.2211 5 13.51 14.23 18.1611 6 13.76 15.51 20.4412 0 11.50 9.00 10.1412 1 11.72 9.72 11.1412 2 11.95 10.51 12.2912 3 12.18 11.39 13.6212 4 12.41 12.37 15.1712 5 12.64 13.46 16.9912 6 12.87 14.68 19.12


5.2 Examples of How toUse the Worksheet

This section contains a set of examplesindicating how to use the worksheetsdescribed in section 5.1. First, Worksheets 1through 3 are filled out in order to comparethe cost-effectiveness of three insulationconfiguration alternatives. This is followedby a series of tables that illustrate how theresults from the worksheet calculations canbe organized to create customizedinformation for making foundationinsulation decisions.

THE WORKSHEET EXAMPLES

You are building a conditioned basementin Knoxville, Tennessee. You would like todetermine the optimum amount offoundation insulation to install on theexterior of the concrete masonry wall incontact with the surrounding soil. Extrudedpolystyrene is available in your local buildingmaterials yard with R-values of 5, 10, and 15.Other key assumptions are that you plan oninstalling a high-efficiency heat pump with aCOP of 2.2 and a SEER of 10.25. The ductsare assumed to be in a conditioned space, buta duct efficiency value of 0.9 is assumed.Your economic criteria are a mortgage rate of11 percent with fuel escalation (including

inflation) of 5 percent per year and assuming30-year life cycle cost analysis.

Working through Worksheet 1 leaves line38 with the cost savings due to insulating foreach case (expressed in dollars per linearfoot): case 1 = $14.46, case 2 = $15.28, case 3= $13.68. The largest value ($15.28) is theoptimum case, R-10 insulation. If you addlines 18 and 34 for case 2 ($1.44) and thendivide this sum into line 4 ($10.87), you seethe simple payback for this case is 7.5 years.The optional worksheets 2 and 3 are alsofilled out for this example.

SAMPLE TABLES GENERATEDFROM THE WORKSHEETS

Tables 5-8 through 5-11 show annualenergy cost savings for a complete set offoundation configurations. For each option,annual savings due to insulating are givenfor cities in five representative U.S. climatezones. The energy savings account forchanges in both heating and cooling loads.These tables allow users to compare thedifferences in performance among thesevarious insulation placements. Also, the costof insulating has been divided by annualsavings to show the simple payback for theinvestment. These savings are based onmedium fuel costs as shown in Table 2-3.Similar customized tables can be generatedusing the worksheets to fit local conditions.



STEP A: IDENTIFY FOUNDATION CHARACTERISTICS

1. Enter foundation type (basement, crawl space, or slab) _____________ _____________ _____________

2. Enter insulation configuration from Table 5-2 _____________ _____________ _____________

3. Enter nominal R-value from Table 5-2 _____________ _____________ _____________

4. Enter installation cost from Table 5-2 or use Worksheet 2[units: $/lin ft or $/sq ft]* _____________ _____________ ____________

STEP B: DETERMINE HEATING CLIMATE

5. Enter heating degree days (HDD) from Table 5-1 _____________ _____________ _____________

STEP C: DETERMINE HEATING LOAD SAVINGS

6. Enter HLFI from Table 5-3 _____________ _____________ _____________

7. Enter HLFS from Table 5-3 _____________ _____________ _____________

8. Multiply line 7 (HLFS) by line 5 (HDD) _____________ _____________ _____________

9. Add lines 6 and 8 [units: Btu/(HDD x UDELTA

)] _____________ _____________ _____________

10. Enter UDELTA

from Table 5-2 (or Worksheet 3) _____________ _____________ _____________


12. Multiply line 11 by line 5 (HDD) _____________ _____________ _____________

13. Divide line 12 by 1,000,000 [units: MBtu/lin ft or sq ft]* _____________ _____________ _____________

STEP D: DETERMINE HEATING ENERGY DOLLAR SAVINGS

14. Enter heating system efficiency from Table 5-6 (HEEF) _____________ _____________ _____________

15. Multiply line 14 by 0.9 (duct efficiency) _____________ _____________ _____________ (see instructions for alternative duct efficiency numbers)

16. Divide line 13 (heating load savings) by line 15 _____________ _____________ _____________

17. Enter heating energy price rate and multiply by conversion factor:

A. Electricity: __________$ per kWh X 293 = _____________ _____________ _____________

B. Natural gas: __________$ per therm X 10 = _____________ _____________ _____________

C. Fuel oil: __________$ per gallon X 7.2 = _____________ _____________ _____________

D. Propane: __________$ per gallon X 10.9 = _____________ _____________ _____________




(NOTE: If cooling energy savings are not to be included in the calculation, go directly to STEP H.)


Worksheet 1: Selection of Optimal Foundation Insulation (Page 1 of 2)—Example



STEP E: DETERMINE COOLING CLIMATE

21. Enter cooling degree hours (CDH) from Table 5-1 _____________ _____________ _____________

STEP F: DETERMINE COOLING LOAD SAVINGS

22. Enter CLFI from Table 5-4 _____________ _____________ _____________

23. Enter CLFS from Table 5-4 _____________ _____________ _____________

24. Multiply line 23 (CLFS) by line 21 (CDH) _____________ _____________ _____________

25. Add lines 22 and 24 [units: Btu/(CDH x UDELTA

)] _____________ _____________ _____________

26. Enter UDELTA

from line 10 ( Table 5-2 or Worksheet 3) _____________ _____________ _____________

27. Multiply line 26 (UDELTA

) by line 25 (CLF) _____________ _____________ _____________

28. Multiply line 27 by line 21 (CDH) _____________ _____________ _____________

29. Divide line 28 by 1,000 [units: KBtu/lin ft or sq ft]* _____________ _____________ ____________

STEP G: DETERMINE COOLING ENERGY DOLLAR SAVINGS

30. Enter cooling system efficiency from Table 5-6 (CEEF) _____________ _____________ _____________

31. Multiply line 30 by 0.9 (duct efficiency) _____________ _____________ _____________

32. Divide line 29 (cooling load savings) by line 31 _____________ _____________ _____________

33. Enter cooling energy electric rate (i.e., $ 0.078 per kWh) _____________ _____________ _____________




STEP H: DETERMINE NET DOLLAR SAVINGS

37. Add line 20 (heating) and line 36 (cooling) _____________ _____________ _____________

38. Subtract line 4 (costs) from line 37 (savings)[units: $/lin ft or sq ft]* _____________ _____________ _____________


Worksheet 1: Selection of Optimal Foundation Insulation (Page 2 of 2)—Example


Worksheet 2: Optional Method for Estimating Insulation Installation Cost—Example

CASE 1 CASE 2 CASE 3STEP A: DETERMINE MATERIAL COST

1. Enter the total material cost of insulation _____________ _____________ _____________

2. Enter the total material cost of fasteners _____________ _____________ _____________

3. Enter the cost of protective covering or required flamespread protection _____________ _____________ _____________

4. Add lines 1, 2, and 3 to determine the total material cost _____________ _____________ _____________

STEP B: DETERMINE LABOR COST

5. Enter site preparation cost _____________ _____________ _____________

6. Enter installation cost for insulation _____________ _____________ _____________

7. Enter installation cost for any framing or furring _____________ _____________ _____________

8. Enter installation cost for any protective covering _____________ _____________ _____________

9. Add lines 5, 6, 7, and 8 to determine total labor cost _____________ _____________ _____________

STEP C: DETERMINE TOTAL INSTALLED COST

10. Add lines 4 and 9 _____________ _____________ _____________

11. Multiply line 10 by the subcontractor markup(example: 1.3) _____________ _____________ _____________

12. Multiply line 11 by the general contractor markup(example: 1.3) _____________ _____________ _____________

13. Divide line 12 by the foundation perimeter lengthin feet _____________ _____________ _____________


Worksheet 3: Optional Method for Determining UDELTA

—Example

CASE 1 CASE 2 CASE 3STEP A: CALCULATE THE U-VALUEOF INSULATION ASSEMBLY

1. Enter the fraction of the total area covered by each component

a. Component 1 (example: insulation) _____________ _____________ _____________

b. Component 2 (example: framing) _____________ _____________ _____________

c. Component 3 _____________ _____________ _____________

d. Component 4 _____________ _____________ _____________

e. Component 5 _____________ _____________ _____________

2. Divide the fractional values in line 1 by the corresponding R-values

a. Line 1a divided by R-value for component 1 _____________ _____________ _____________

b. Line 1b divided by R-value for component 2 _____________ _____________ _____________

c. Line 1c divided by R-value for component 3 _____________ _____________ _____________

d. Line 1d divided by R-value for component 4 _____________ _____________ _____________

e. Line 1e divided by R-value for component 5 _____________ _____________ _____________

3. Add the results of line 2 to determine the overall U-value

(2a + 2b + 2c + ...) _____________ _____________ _____________

STEP B: CALCULATE THE EFFECTIVE R-VALUE (REFF

)

4. Enter the appropriate RBASE

from Table 5-5 _____________ _____________ _____________

5. Divide 1 by line 3 _____________ _____________ _____________

6. Add lines 4 and 5 to determine REFF

_____________ _____________ _____________

STEP C: DETERMINE THE U-VALUE OF UNINSULATED CASE (UBASE

)

7. Enter RBASE

from Table 5-5 _____________ _____________ _____________

8. Enter RSOIL

from Table 5-5 _____________ _____________ _____________

9. Add lines 7 and 8 _____________ _____________ _____________


STEP D: DETERMINE THE U-VALUE OF INSULATED CASE (UTOTAL

)

11. Add line 6 (REFF

) and line 8 (RSOIL

) _____________ _____________ _____________


STEP E: DETERMINE U-VALUE DIFFERENCE (UDELTA

)

13. Subtract line 12 from line 10 [units: Btu/OF x ft2 x h] _____________ _____________ _____________


Table 2-1: Installation Costs and Energy Cost Savings for Fully-Conditioned Deep Basements

CONFIGURATION DESCRIPTIONINSTALL.COST($ PER LF)

ANNUAL ENERGY COST SAVINGS IN $ PER LINEAL FOOT(SIMPLE PAYBACK SHOWN IN PARENTHESES)

0-2000 HDD(LOS ANG)



6-8000 HDD(CHICAGO)

8-10000 HDD(MPLS)

EXTERIOR: HALF WALL

EXTERIOR: FULL WALL

INTERIOR: FULL WALL

WOOD: FULL WALL



8 FT: R-6 RIGID

8 FT: R-8 RIGID

8 FT: R-11 BATT

8 FT: R-19 BATT

8 FT: R-5 RIGID

8 FT: R-10 RIGID

8 FT: R-15 RIGID

8 FT: R-20 RIGID

4 FT: R-5 RIGID

4 FT: R-10 RIGID

8 FT: R-11 BATT

8 FT: R-19 BATT

8 FT: R-30 BATT

4.44

6.54

7.01

10.87

14.55

18.35

2.44

3.79

9.70

0.22

0.25

0.27

0.33

0.35

0.37

0.27

0.29

0.33

0.37

0.12

0.15

0.17

0.91

1.07

1.10

1.32

1.42

1.48

1.12

1.19

1.33

1.47

0.49

0.58

0.65

1.11

1.32

1.40

1.70

1.84

1.92

1.42

1.52

1.72

1.90

0.67

0.81

0.91

1.32

1.55

1.65

2.00

2.16

2.25

1.67

1.79

2.02

2.23

0.78

0.94

1.06

1.64

1.93

2.06

2.51

2.72

2.84

2.09

2.24

2.53

2.82

0.98

1.20

1.35


(20.2)

(26.2)

(4.9)

(6.1)

(4.0)

(5.0)

(3.4)

(4.2)

(2.7)

(3.4)

(26.0)

(33.0)

(41.6)

(49.6)

(6.4)

(8.2)

(10.2)

(12.4)

(5.0)

(6.4)

(7.9)

(9.6)

(4.2)

(5.4)

(6.7)

(8.2)

(3.4)

(4.3)

(5.3)

(6.5)

(20.3)

(25.3)

(57.1)

(5.0)

(6.5)

(14.9)

(3.6)

(4.7)

(10.7)

(3.1)

(4.0)

(9.2)

(2.5)

(3.2)

(7.2)

INTERIOR: FULL WALL 8 FT: R-6 RIGID

8 FT: R-8 RIGID

8 FT: R-11 BATT

8 FT: R-19 BATT

0.28

0.30

0.33

0.37

1.14

1.21

1.35

1.47

1.46

1.55

1.74

1.91

1.72

1.83

2.04

2.24

2.15

2.29

2.57

2.82


4.72

5.76

6.48

10.24

12.32

13.36

12.56

16.32

(17.5)

(19.9)

(19.6)

(27.7)

(4.2)

(4.8)

(4.9)

(7.0)

(3.3)

(3.8)

(3.8)

(5.4)

(2.8)

(3.2)

(3.2)

(4.6)

(2.3)

(2.6)

(2.6)

(3.6)

(44.0)

(44.5)

(38.1)

(44.1)

(10.8)

(11.0)

(9.3)

(11.1)

(8.4)

(8.6)

(7.2)

(8.5)

(7.2)

(7.3)

(6.2)

(7.3)

(5.7)

(5.8)

(4.9)

(5.8)

Table 5-8: Energy Cost Savings and Simple Paybacks for Conditioned Basements

Energy cost savings in this table are based on medium fuel prices shown in Table 2-3.




0-2000 HDD(LOS ANG)



6-8000 HDD(CHICAGO)

8-10000 HDD(MPLS)

EXTERIOR: HALF WALL

EXTERIOR: FULL WALL

INTERIOR: FULL WALL

WOOD: FULL WALL



8 FT: R-6 RIGID

8 FT: R-8 RIGID

8 FT: R-11 BATT

8 FT: R-19 BATT

8 FT: R-5 RIGID

8 FT: R-10 RIGID

8 FT: R-15 RIGID

8 FT: R-20 RIGID

4 FT: R-5 RIGID

4 FT: R-10 RIGID

8 FT: R-11 BATT

8 FT: R-19 BATT

8 FT: R-30 BATT

4.44

6.54

7.01

10.87

14.55

18.35

2.44

3.79

9.70

0.03

0.04

0.04

0.05

0.05

0.05

0.04

0.04

0.05

0.05

0.03

0.04

0.04

0.13

0.16

0.13

0.14

0.14

0.15

0.13

0.13

0.14

0.15

0.??

0.05

0.05

0.23

0.28

0.25

0.32

0.35

0.37

0.25

0.28

0.32

0.37

0.16

0.18

0.21

0.30

0.36

0.36

0.45

0.51

0.54

0.36

0.40

0.46

0.53

0.23

0.27

0.32

0.41

0.50

0.51

0.65

0.72

0.77

0.52

0.57

0.66

0.76

0.31

0.39

0.45


(148)

(163)

(34.2)

(40.9)

(19.3)

(23.4)

(14.8)

(18.2)

(10.8)

(13.1)

(175)

(217)

(291)

(367)

(53.9)

(77.6)

(104)

(122)

(28.0)

(34.0)

(41.6)

(49.6)

(11.7)

(24.2)

(28.5)

(34.0)

(13.7)

(16.7)

(20.2)

(23.8)

(81.3)

(94.8)

(243)

()

(75.8)

(194)

(15.3)

(21.1)

(46.2)

(10.6)

(14.0)

(30.3)

(7.9)

(9.7)

(21.6)


CEILING

E: Concrete or Masonry Foundation Walls with Ceiling Insulation

R-11 BATT

R-19 BATT

R-30 BATT

0.34

0.52

0.86

0.01

0.01

0.01

0.01

0.01

0.00

0.04

0.05

0.06

0.06

0.07

0.10

0.09

0.10

0.15

(34.0)

(52.0)

(86.0)

(34.0)

(52.0)

(8.6)

(10.4)

(14.3)

(5.7)

(7.4)

(8.6)

(3.8)

(5.2)

(5.7)

ANNUAL ENERGY COST SAVINGS IN $ PER SQUARE FOOT(SIMPLE PAYBACK SHOWN IN PARENTHESES)

INTERIOR: FULL WALL 8 FT: R-6 RIGID

8 FT: R-8 RIGID

8 FT: R-11 BATT

8 FT: R-19 BATT

0.04

0.04

0.05

0.05

0.13

0.13

0.14

0.15

0.26

0.29

0.33

0.37

0.38

0.41

0.47

0.53

0.54

0.58

0.67

0.76


4.72

5.76

6.48

10.24

12.32

13.36

12.56

16.32

(118)

(144)

(130)

(205)

(36.3)

(44.3)

(46.3)

(68.3)

(18.9)

(20.6)

(20.3)

(27.7)

(13.1)

(14.4)

(14.1)

(19.3)

(9.1)

(10.1)

(9.8)

(13.5)

(308)

(344)

(251)

(326)

(98.4)

(103)

(89.7)

(109)

(47.4)

(46.1)

(38.1)

(44.1)

(32.4)

(32.6)

(26.7)

(30.8)

(22.8)

(23.0)

(18.7)

(21.5)

Table 5-9: Energy Cost Savings and Simple Paybacks for Unconditioned Basements



Table 5-10: Energy Cost Savings and Simple Paybacks for Crawl Space Foundations



0-2000 HDD(LOS ANG)



6-8000 HDD(CHICAGO)

8-10000 HDD(MPLS)

EXTERIOR VERTICAL

INTERIOR VERTICAL

WITHIN WOOD WALL



2 FT: R-5 RIGID

2 FT: R-10 RIGID

2 FT: R-5 RIGID

2 FT: R-10 RIGID

2 FT: R-11 BATT

2 FT: R-19 BATT

2.00

2.97

1.32

1.76

0.04

0.04

0.04

0.04

0.02

0.02

0.15

0.18

0.13

0.15

0.06

0.06

0.25

0.30

0.32

0.28

0.10

0.12

0.30

0.35

0.30

0.35

0.12

0.15

0.39

0.47

0.38

0.46

0.17

0.21


(50.0)

(74.3)

(13.3)

(16.5)

(8.0)

(9.9)

(6.7)

(8.5)

(5.1)

(6.3)

(66.0)

(88.0)

(22.0)

(29.3)

(13.2)

(14.7)

(11.0)

(11.7)

(7.8)

(8.4)


CEILINGD: Vented Crawl Space - Concrete or Masonry Foundation Walls with Ceiling Insulation

R-11 BATT

R-19 BATT

R-30 BATT

0.34

0.52

0.86

0.04

0.05

0.05

0.06

0.06

0.07

0.10

0.12

0.13

0.15

0.18

0.19

0.19

0.23

0.25

(8.5)

(10.4)

(17.2)

(5.7)

(8.7)

(12.3)

(3.4)

(4.3)

(6.6)

(2.3)

(2.9)

(4.5)

(1.8)

(2.3)

(3.4)

ANNUAL ENERGY COST SAVINGS IN $ PER SQUARE FOOT(SIMPLE PAYBACK SHOWN IN PARENTHESES)

INTERIOR VERTICALAND HORIZONTAL 2 FT/2 FT: R-5 RIGID




0.05

0.06

0.05

0.05

0.13

0.11

0.14

0.12

0.27

0.35

0.30

0.34

0.37

0.37

0.41

0.43

0.50

0.53

0.57

0.62

1.15

2.12

2.28

3.42

4.24

6.36

(28.8)

(53.0)

(8.8)

(14.1)

(3.6)

(7.6)

(3.8)

(6.1)

(3.0)

(4.6)

(45.6)

(57.0)

(84.8)

(127)

(17.5)

(31.1)

(30.3)

(53.0)

(8.4)

(9.8)

(14.1)

(18.7)

(6.2)

(9.2)

(10.3)

(14.8)

(4.6)

(6.5)

(7.4)

(10.3)





0-2000 HDD(LOS ANG)



6-8000 HDD(CHICAGO)

8-10000 HDD(MPLS)

EXTERIOR VERTICAL

INTERIOR VERTICAL

INTERIOR HORIZONTAL


C: Concrete or Masonry Foundation Walls with Interior Insulation Placed Horizontally Under Slab Perimeter

2 FT DEEP: R-5

2 FT DEEP: R-10

4 FT DEEP: R-5

4 FT DEEP: R-10

4 FT DEEP: R-15

4 FT DEEP: R-20

2 FT DEEP: R-5

2 FT DEEP: R-10

4 FT DEEP: R-5

4 FT DEEP: R-10

4 FT DEEP: R-15

4 FT DEEP: R-20

2 FT WIDE: R-5

2 FT WIDE: R-10

4 FT WIDE: R-5

4 FT WIDE: R-10

2.25

3.50

3.53

5.70

7.69

9.68

1.65

2.80

2.69

4.52

0.03

0.03

0.03

0.04

0.04

0.04

0.03

0.03

0.03

0.04

0.04

0.04

0.03

0.03

0.03

0.03

0.13

0.16

0.16

0.19

0.20

0.21

0.12

0.13

0.14

0.16

0.17

0.17

0.11

0.12

0.12

0.12

0.29

0.34

0.35

0.43

0.46

0.48

0.27

0.30

0.33

0.39

0.41

0.42

0.26

0.29

0.31

0.34

0.35

0.41

0.43

0.52

0.56

0.59

0.32

0.36

0.40

0.47

0.50

0.52

0.32

0.36

0.40

0.47

0.40

0.47

0.49

0.60

0.65

0.68

0.38

0.43

0.48

0.57

0.60

0.62

0.39

0.44

0.49

0.56


(75.0)

(117)

(118)

(142)

(192)

(242)

(17.3)

(21.9)

(22.1)

(30.0)

(38.5)

(46.1)

(7.8)

(10.3)

(10.1)

(13.3)

(16.7)

(20.2)

(6.4)

(8.5)

(8.2)

(11.0)

(13.7)

(16.4)

(5.6)

(7.4)

(7.2)

(9.5)

(11.8)

(14.2)

(55.0)

(93.3)

(89.7)

(151)

(15.0)

(23.3)

(22.4)

(37.7)

(6.3)

(9.7)

(8.7)

(13.3)

(5.2)

(7.8)

(6.7)

(9.6)

(4.2)

(6.4)

(5.5)

(8.1)

EXTERIOR HORIZONTAL

D: Concrete or Masonry Foundation Walls with Exterior Insulation Extending Outward Horizontally2 FT WIDE: R-5

2 FT WIDE: R-10

4 FT WIDE: R-5

4 FT WIDE: R-10

0.28

0.26

0.27

0.25

0.47

0.48

0.47

0.48

0.51

0.53

0.52

0.56

0.56

0.60

0.58

0.63

(118)

(190)

(148)

(263)

(12.6)

(21.9)

(16.4)

(31.6)

(7.5)

(11.9)

(9.4)

(16.5)

(6.9)

(10.8)

(8.5)

(14.1)

(6.3)

(9.5)

(7.6)

(12.5)

1.30

2.19

2.59

4.40

6.23

8.06

(43.3)

(73.0)

(86.3)

(110)

(156)

(201)

(10.8)

(16.8)

(18.5)

(27.5)

(36.6)

(47.4)

(4.8)

(7.3)

(7.8)

(11.3)

(15.2)

(19.2)

(4.1)

(6.1)

(6.5)

(9.4)

(12.5)

(15.5)

(3.4)

(5.1)

(5.4)

(7.7)

(10.4)

(13.0)

3.53

5.70

4.43

7.90

0.03

0.03

0.03

0.03

Table 5-11: Energy Cost Savings and Simple Paybacks for Slab-on-Grade Foundations



American Concrete Institute (ACI) 1980.Guide to Concrete Floor and Slab Construction,302.1R-80, 46 pp., Detroit, Michigan.

American Concrete Institute (ACI) 1983.Construction of Slabs on Grade, SCM4-83, 96pp., Detroit, Michigan.

ASHRAE 1989a. ASHRAE Standard 62-1989,Ventilation for Acceptable Indoor Air Quality,American Society of Heating ,Refrigerating, and Air-ConditioningEngineers, Inc., Atlanta, Georgia.

ASHRAE 1989b. ASHRAE Standard 90.2PDraft 89-1, American Society of Heating,Refrigeration, and Air-ConditioningEngineers, Atlanta, Georgia, March, 1989.

Christian, J.E., Strzepek, W. R. 1987.Procedure for Determining the OptimumFoundation Insulation Levels for New,Low-Rise Residential Buildings, ASHRAETransactions, V. 93, Pt. 1, January, 1987.

Christian, J.E. 1989. Worksheet for Selectionof Optimal Foundation Insulation,Conference on Thermal Performance of theExterior Envelopes of Buildings IV, Orlando,Florida, December 4-7, 1989.

Council of American Building Officials 1989.Model Energy Code, 1989 Edition, TheCouncil of American Building Officials,Falls Church, Virginia, March, 1989.

Dudney, C.S., Hubbard, L.M., Matthews,T.G., Scolow, R.H., Hawthorne, A.R.,Gadsby, K.J., Harrje, D.T., Bohac, D.L.,Wilson, D.L. 1988. Investigation of RadonEntry and Effectiveness of Mitigation Measuresin Seven Houses in New Jersey, ORNL-6487,Draft, September, 1988.

EPA 1987. Radon Reduction in NewConstruction: An Interim Guide, United

States Environmental Protection Agency,Offices of Air and Radiation and Researchan Development, Washington, D.C., 20460,EPA-87-009, August, 1987.

EPA 1986. Radon Reduction Techniques forDetached Houses: Technical Guidance, 50 pp.,EPA/625/5-86/019.

Labs, K., Carmody, J., Sterling, R., Shen, L.,Huang, Y.J., Parker, D. 1988. BuildingFoundation Design Handbook, ORNL/Sub/86-72143/1, May, 1988.

Jones, R.A. 1980. Crawl Space Houses, CircularSeries F4.4, Small Homes Council/BuildingResearch Council, Univ. of Illinois, Urbana-Champaign, Illinois, 8 pp.

National Council on Radiation Protectionand Measurements (NCRP) 1984.Evaluation of Occupational and EnvironmentalExposures to Radon and Radon Daughters inthe United States. NCRP Report 78.Washington, D.C.: National Council onRadiation Protection and Measurements.

National Forest Products Association (NFPA)1987. Permanent Wood Foundation System;Design, Fabrication and Installation Manual,NFPA, Washington, D.C., September, 1987.

Nero, A. V. 1986. “The Indoor Radon Story,”Technology Review, January, 1986.

Sextro, R.G., Moed, B.A., Nazaroff, W.W.,Revzan, K.L., and Nero, A.V. 1987.Investigations of Soil as a Source of IndoorRadon, ACS Symposium Series Radon andIts Decay Products Occurrence, Properties,and Health Effects, American ChemicalSociety.

U. S. Census 1987. Statistical Abstracts of theUnited States, 107th edition.

References

A

Air management, 9, 20-23, 46-47, 66-69Air space, 18, 30, 32Anchor bolts, 16, 31-32, 43, 53-54, 63, 75Assumptions used in insulation analysis, 15,

41-42, 62

B

Backfill, 17, 31-32, 35, 53Basement

checklist, 33-37details, 24-32drainage/waterproofing measures, 17,

31, 35insulation, 10-15, 18, 31-32, 91-92,

104-105radon control techniques, 20-23, 31, 37structural design, 16, 31-32termite/wood decay control techniques,

18-19, 36Bond beams, 18, 32, 45, 54, 65, 67Brick veneer, 71, 74-75Builder/subcontractor markup, 15, 41, 62, 86Building permits/plans, 37, 58, 79

C

Caulking, 31, 53, 66Ceiling insulation

crawl space, 39-41, 44-45, 54, 93, 106unconditioned basement, 11-15, 18, 32,

92, 105Checklists, 33-37, 55-58, 76-79Climate data, 89-90Collection system, soil gas, 21-23, 67-69Concrete foundation wall

details, 25-26, 28-29, 49, 51-54, 72-73insulation placement, 11-15, 39-43, 60-62,

64-65structural design, 16, 31-32, 34, 53-54, 63-

65, 75

Concrete shrinkage cracking, minimizing, 16,20-21, 31, 63, 67, 75

Construction costs, 7Construction details

basement, 24-32crawl space, 48-54slab-on-grade foundation, 70-75

Control joints, 21, 67Cooling degree hours, 81, 84-85, 89-90Cooling load factor coefficients, 96Cooling system SEER, 15, 41, 62, 97Cost savings, energy, 82, 104-107Costs, insulation installation, 14-15, 40-41,

61-62, 86Costs, labor/material, 7, 86Crawl space

checklist, 55-58details, 48-54drainage/waterproofing techniques,

43-44, 53insulation, 38-42, 44-45, 53-54, 93, 106radon control techniques, 42, 46-47, 58structural design, 42-43, 53-54, 56termite/wood decay control techniques,

45-46, 57vented vs. unvented, 38, 40, 43vents, 38, 43, 47, 54

D

Dampproofing, 17, 21, 31, 35, 43-44Decay control, wood, 18-19, 36, 45-46, 57,

65-66, 78Depressurization, 21-23, 67-69Design decisions, 4-7Details, construction

basement, 24-32crawl space, 48-54slab-on-grade foundation, 70-75

Discharge system, 21-23, 67-69Dollar savings, 82-85Downspouts, 18, 20, 43, 45, 63, 65Drainage systems, 17, 31-32, 35, 43-44, 53,

63-64

Index


Drainpipes, 23, 31-32, 53, 67Duct/pipe insulation, 11, 15, 18, 41, 43

E

Effective R-values, 97Energy cost savings, 82, 104-107EPS insulation, 18, 31-32, 45, 53-54, 75Equipment efficiencies, heating and cooling,

15, 41, 62, 97Expansive soil, 6, 16, 43, 63

F

Fans, discharge, 21-23, 69Fiberglass insulation, 31, 53Filter fabric, 31, 53Flame spread/fire retardant, 32, 45, 53, 86Floor/slab, 20-21, 32, 34, 63-65Footing

basement, 16, 31-33crawl space, 42-43, 53-54, 56slab-on-grade, 63-65, 75, 77

Formulas, worksheet, 81, 88Foundations, introduction to, 1-7Frost penetration depth, 16, 31, 43, 53, 63-64,

75Fuel price assumptions, 14, 41, 61

G

Gaskets, 28, 32Grade beams, 63-64, 71, 75Gravel bed/layer, 31-32, 43, 67-69, 75Gutters, 18, 20, 43, 45, 63, 65

H

Heating degree days, 82, 89-90Heating equipment efficiencies, 15, 41, 62, 97Heating load factor coefficients, 95Horizontal insulation, 40-41, 45, 60-62, 64, 94,

107

I

Insulationbasement, 10-15, 18, 31-32, 91-92, 104-105configurations, 10-15, 38-42, 59-62crawl space, 38-42, 44-45, 53-54, 93, 106energy savings, 82, 104-107exterior vs. interior placement, 18, 44-45,

62, 64

horizontal placement, 40-41, 45, 60-62,64, 94, 107

installation costs, 14-15, 40-41, 61-62, 86R-values and costs, 94slab-on-grade foundation, 59-62, 64-65,

75, 94, 107See also Ceiling insulation; Subslab

insulationIsolation joints, 31, 66, 75

L

Labor/material costs, 7, 86Life cycle cost analysis, 11, 40, 61, 80-88Loads, lateral/vertical, 16, 42, 63

M

Market preferences, 7Markup, builder/subcontractor, 15, 41, 62,

86Masonry foundation wall

details, 27, 50, 72-74insulation, 11-15, 39-43, 60-62, 64-65structural design, 16, 32, 53-54, 63, 65, 75

MEPS insulation, 31-32, 53-54, 75Moistureproofing. See Dampproofing or

WaterproofingMortgage rates, 82, 85, 98

P

Paybacks, 11, 40, 62, 104-107Piles/piers, 43Plans/permits, 37, 58, 79Plumbing, 20-21, 67Polystyrene, 18, 31-32, 45, 53-54, 75Porches, 19, 46, 66

R

Radonbasement design techniques, 20-23, 31,

37collection/discharge systems, 21-23, 67-

69crawl space design techniques, 42, 46-47,

58general mitigation techniques, 8-9slab considerations, 66-69, 79

Reinforcing, 16, 31-32, 54, 67, 75Rim joists, 18, 32, 44R-TOTAL, R-BASE, R-EFF, 88R-VALUES, effective, 97

S

Scalar ratios, 82, 85, 98Seismic design considerations, 16, 43, 63Shrinkage cracking, minimizing, 16, 20-21,

31, 63, 67, 75Sill plate

basement, 18-19, 31crawl space, 44-46, 53slab-on-grade, 65, 75

Site considerations, 6Site inspection, 37, 58, 79Sitework, 33, 55, 76Slab-on-grade foundation

checklists, 76-79details, 70-75drainage/waterproofing, 63-64, 75insulation, 59-62, 64-65, 75, 94, 107radon control techniques, 66-69, 79structural design, 63-65, 75, 77termite/wood decay control techniques,

65-66, 78Slabs, concrete, 16, 31-32, 34, 63-67, 75-76Slab/wall joints, 19-20, 60-66Soil. See Backfill; Expansive soil; Frost

penetration depthSoil gas. See RadonStack pipes/effects, 22-23, 67-69Standpipes, 22-23, 67-69Subdrainage, 17, 31-32, 35, 43-44, 53Subslab insulation, 32, 61-62, 73-75, 94, 107Sumps, 21-23, 44Surface drainage, 17, 31-32, 35, 43-44, 53, 63-

64, 75

T

Termite/wood decay control, 18-19, 36, 45-46, 57, 65-66, 78

U

U-DELTA, 82-88Underfloor/underslab insulation, 32, 61-62,

73-75, 94, 107

V

Vapor retarder/controlbasement, 18, 31-32, 36crawl space, 45, 47, 53-54, 57slab-on-grade foundation, 75, 78

Ventilation. See Air management; Crawl space;Radon

Vents, 38, 42, 47, 54

W

Walls, foundation. See Concrete foundationwall; Masonry foundation wall; Woodfoundation wall

Waterproofing, 17, 31, 35, 43-44, 53, 63-64Weather data, 89-90Weep holes, 23, 32, 67Welded wire fabric, 16, 20, 31, 63, 67, 75Wood decay control, 18-19, 36, 45-46, 57, 65-

66, 78Wood foundation wall

detail, 30insulation, 11-15, 39-43, 91-93, 104-106structural design, 16, 18, 32, 45

Worksheets, 80-88, 100-103

X

XEPS insulation, 31-32, 53-54, 75

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