Code Req Insulation Ventilation

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CODE

REQUIREMENTS ANDENERGY ANALYSIS

OF INSULATION ANDVENTILATION FOR

GAS-FIREDEQUIPMENT ROOMSCopyright 2001 American Gas AssociationAll Rights Reserved

Prepared forCodes, Standards and Technical Support

American Gas Association,400 N. Capitol St., NWWashington, DC 20001

Prepared bySteven V. Stoltz, P. E.

November 2001


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Disclaimer

This report was prepared by Energy International, Inc. as an account of work sponsoredby the American Gas Association (AGA). Neither AGA, members of AGA, nor any

person acting on behalf of either:

a. Makes any warranty or representation with respect to the accuracy, completeness,or usefulness of the information contained in this report, or that the use of anyinformation disclosed in this report may not infringe privately owned rights; or

b. Assumes any liability with respect to the use of, or for damages resulting from theuse of, any information disclosed in this report.


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TABLE OF CONTENTS

INTRODUCTION ...............................................................................................................1

BACKGROUND ...................................................................................................................1

GOALS AND OBJECTIVES ...................................................................................................2

SUMMARY OF RESULTS ................................................................................................2

REVIEW OF GAS AND ENERGY CODES ...............................................................................2SUMMARY OF ENGINEERING ANALYSIS.............................................................................3

GAS AND ENERGY CODES AND STANDARDS..........................................................4

EQUIPMENT ROOM INSULATION REQUIREMENTS...............................................................4International Energy Conservation Code 2000 (IECC) ...............................................5

ASHRAE Standard 90.2-1993, Energy Efficient Design of Low-Rise Residential

Buildings .......................................................................................................................6

UNUSUALLY TIGHT CONSTRUCTION..................................................................................8National Fuel Gas Code (1999) Definition of Unusually Tight Construction..............9

International Fuel Gas Code (2000) Definition of Unusually Tight Construction.......9

INFILTRATION AND VENTILATION....................................................................................11

ENGINEERING ANALYSIS............................................................................................12

OVERVIEW OF METHODOLOGY........................................................................................12SUMMARY OF RESULTS ...................................................................................................13SCENARIO DEVELOPMENT ...............................................................................................17

Water Heater Categories ............................................................................................17

Furnace and Space Heating Equipment Categories ...................................................18

Equipment Room Thermal Characteristics.................................................................18Appliance Characteristics...........................................................................................19

Climate Data ...............................................................................................................21

Energy Costs ...............................................................................................................22

EQUIPMENT ROOM TEMPERATURES AND ANNUAL ENERGY COSTS FOR SIX CITIES ........22Atlanta .........................................................................................................................25

Baltimore.....................................................................................................................26

Chicago .......................................................................................................................27

Houston .......................................................................................................................28

Seattle..........................................................................................................................29

CONCLUSIONS AND RECOMMENDATIONS ............................................................30

CONCLUSIONS .................................................................................................................30RECOMMENDATIONS .......................................................................................................31

APPENDIX A -- INFILTRATION AND VENTILATION CODES AND STANDARDS32

International Energy Conservation Code (IECC 2000) .............................................32

ASHRAE Standard 90.2 - 1993 ...................................................................................34


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ASHRAE Standard 90.2 Ventilation Requirements.....................................................36

ASHRAE Standard 62-1999, Ventilation for Acceptable Indoor Air Quality .............36

List of FiguresFigure 1. Equipment Room Temperature and Thermal Balance ......................................14

List of Tables

Table 1. Annual Energy Savings/Costs for Additional Insulation....................................15Table 2. Annual Energy Benefits and Costs for Outside Combustion Air.......................16Table 3. Equipment Room Thermal Properties ................................................................19Table 4. Equipment Characteristics and Combinations Considered for Further Study....20Table 5. Average January and ASHRAE Heating Design Temperatures..........................22Table 6. Equipment Room Design Heating Temperatures -- Atlanta...............................25Table 7. Annual Energy Costs -- Atlanta..........................................................................25

Table 8. Equipment Room Design Heating Temperatures -- Baltimore ..........................26Table 9. Annual Energy Costs -- Baltimore ......................................................................26Table 10. Equipment Room Design Heating Temperatures -- Chicago...........................27Table 11. Annual Energy Costs -- Chicago ......................................................................27Table 12. Equipment Room Design Heating Temperatures -- Houston............................28Table 13. Annual Energy Costs -- Houston......................................................................28Table 14. Equipment Room Design Heating Temperatures -- Seattle .............................29

Table 15. Annual Energy Costs -- Seattle.........................................................................29


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INTRODUCTION

This report provides an analysis of existing gas and energy codes and standards withinterpretations relative to the ventilation and insulation of residential gas-fired equipmentrooms. This report also presents a methodology for evaluating the temperatures and

energy use associated with equipment rooms that are provided with outside air forcombustion. Results of the energy analysis are presented for a variety of typical gas-firedequipment and for climate data from five major U.S. cites.

BACKGROUND

One interpretation of the Model Energy Code 1995 Edition Commentary implies thatwhen a space is directly ventilated with outside air, such as an equipment room providedwith outside combustion air, that space is unconditioned and outside the thermalenvelope. This interpretation requires the addition of insulation to the walls and other

surfaces separating such a ventilated equipment room from any adjoining conditionedspaces.

A conditioned space is typically any space that does not communicatedirectly to the outside (i.e., that is not directly ventilated to the outdoors)1

Energy codes and standards define the thermal envelope as comprising the surfacesseparating conditioned spaces from the exterior environment or unconditioned spaces.The surfaces that comprise the thermal envelope are subject to the insulation and airleakage requirements that are applicable to exterior surfaces in general. The question of

interest is whether the surfaces that separate a conditioned space from a gas-firedequipment space should be considered as part of the thermal envelope when theequipment room is directly ventilated with outside air for combustion.

The potential problems presented by the interaction of improved appliance efficiency,tight construction and mechanical exhaust systems have been widely recognized andstudied. Accordingly, gas codes require that naturally ventilated gas-fired applianceslocated in structures with unusually tight construction (UTC) must be provided withcombustion air from outside. At the same time it appears that the energy code criteria forinfiltration control are roughly equivalent to the gas code definitions of unusually tightconstruction. Thus it is often assumed that energy standards require unusually tight

construction and therefore gas fired equipment rooms must be provided with outside airfor combustion.

1Model Energy Code 1995 Edition Commentary, page 30, Council of AmericanBuilding Officials, International Code Council, Inc. March 1998


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GOALS AND OBJECTIVES

While the broader issues of depressurization and potential venting failure are important,this study is focused primarily on the energy costs and interpretations of energy codesrelating to equipment rooms with outside combustion air.

The goal of this study is to provide an energy engineering perspective on the issuesrelating to the ventilation and insulation of equipment rooms for fuel-burning appliances.It is hoped that this will facilitate a broader understanding of the issues allowing thedevelopment of designs to minimize cost and energy consumption without compromisingair quality or life safety.

One objective of this report is to review and interpret existing energy and gas codes todetermine whether equipment rooms that are directly ventilated with outside air shouldbe insulated from adjacent conditioned spaces. Another objective of this report is toevaluate the cost effectiveness of such insulation. In addition, the energy costs associated

with the choice of either interior or outside air for combustion and ventilation are

compared.

SUMMARY OF RESULTS

In general, gas, energy, and ventilation codes and standards acknowledge that tightconstruction, mechanical exhaust systems and fireplaces may require the introduction ofadditional outside makeup air to avoid interference with fuel burning appliancesHowever, these codes and standards do not provide a consistent approach to determinesuch a requirement or how best to satisfy it.

As to whether confined and directly ventilated equipment rooms should be insulated fromadjacent conditioned spaces, energy codes and standards appear to agree that additionalinsulation is not required if the heat from the equipment maintains the temperature in theequipment room at 50

oF or above. Using the engineering model developed for this

report, it was found that temperatures of 50oF or above are maintained under most

conditions in ventilated equipment rooms with a variety of equipment configurations andclimate data.In addition, the model shows that insulating the equipment room from adjacentconditioned spaces increases energy consumption and cost in most cases. Furthermore,the model shows that in many cases, using air from the conditioned space for combustionreduces total energy costs as compared to directly venting outside combustion air to a

confined equipment room.

REVIEW OF GAS AND ENERGY CODES

Gas and energy codes and standard provide interrelated provisions for the insulation andventilation of spaces containing fuel-burning equipment. Equipment room insulationrequirements from the IECC and ASHRAE 90.2 are dependent on the temperature


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maintained in the room by the release of heat from the equipment in the room. If aminimum temperature of 50

oF is maintained, the equipment room is a conditioned space

and insulation is not required in walls between conditioned spaces.The problem with this temperature-based performance criteria is that it cannot be verifiedby simple inspection of the building or its plans. Performance criteria require either

measurements for a completed buildings or engineering estimates for proposed designs.The provision of outside air for combustion does not, in and of itself, make an equipmentroom an unconditioned space.

Unusually tight construction is defined with minor variations by both the NFGC and theIFGC. These gas code definitions are compared with energy related requirements andrecommendations from the IECC and ASHRAE 90.2. A detailed review of theserequirements shows that compliance with energy codes or standards does not necessarilyrequire unusually tight construction.

SUMMARY OF ENGINEERING ANALYSIS

To address temperature based performance criteria, a thermal analysis model has beendeveloped to calculate equipment room temperatures given the characteristics of theequipment room and the temperatures in the adjoining conditioned space and outside.Using this model, equipment room temperatures were evaluated for a variety of typicalequipment room characteristics and climate data. It was found that temperatures of 50

oF

or greater were maintained under most conditions.

The analysis also shows that the addition of insulation to the walls and other surfacesseparating an equipment room from other conditioned spaces will increase total energy

costs in most cases. Energy costs will be increased where the additional insulationreduces beneficial heat gain from the equipment room to the conditioned space duringmild heating load conditions. Additional insulation was found to be beneficial only forequipment rooms with water heaters in climates dominated by cooling costs. In no casewere the energy cost savings of insulating the equipment room from adjacent conditionedspaces sufficient to justify the additional cost of insulated construction.

The energy analysis also shows that providing confined equipment spaces withcombustion air from outside, rather than air from the conditioned space, does notnecessarily reduce energy consumption. Although the use of outside air for combustionreduces infiltration losses to the conditioned space, this outside air also reduces the

equipment room temperature and the net flow of useful heat to the conditioned spaceduring the heating season.


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GAS AND ENERGY CODES AND STANDARDS

Gas and energy codes and standard provide interrelated provisions that affectrequirements for the insulation and ventilation of spaces containing fuel-burningequipment. The review and consideration of these interrelated provisions are organized

in three subsections:

Equipment room insulation

Unusually tight construction

Infiltration and Ventilation

Equipment room insulation requirements from the IECC and ASHRAE 90.2 aredependent on the temperature maintained in the equipment room by the release of heatfrom the equipment in the room. If a minimum temperature of 50oF is maintained, theequipment room can be considered as a conditioned space and insulation is not requiredin walls between conditioned spaces. The provision of outside air for combustion does

not, in and of itself, make an equipment room an unconditioned space.

Unusually tight construction is defined with minor variations by both the NFGC and theIFGC. These gas code definitions are compared with energy related requirements andrecommendations from the IECC and ASHRAE 90.2. A detailed review of theserequirements shows that compliance with energy codes or standards does not requireunusually tight construction.

Infiltration and ventilation requirements from the IECC, ASHRAE 90.2, and ASHRAE62 are reviewed with emphasis on provisions relating to combustion air requirements,overall infiltration rates and unusually tight construction. This review provides a generalbackground and is included in Appendix A.

EQUIPMENT ROOM INSULATION REQUIREMENTS

Energy codes and standards specify a minimum level of thermal resistance for theceiling, walls, floor and other surfaces that separate conditioned spaces from the outsideor from unconditioned spaces. Questions relating to the insulation of equipment roomsmust first consider whether the equipment room should be classified as a conditionedspace or an unconditioned space as defined by the energy codes and standards.

If the equipment room is an unconditioned space, then insulation would be required insurfaces adjoining conditioned spaces. Although not required, the insulation equpmentroom surfaces adjoining other unconditioned spaces or the outside should be consideredto ensure the reliable operation of equipment and prevent freezing.If the equipment room is a conditioned space, then insulation would be required in thewalls and other surfaces separating the equipment room from the outside orunconditioned spaces such as unheated garages. In this case, insulation would not be


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required in the walls and other surfaces separating the equipment room from otherconditioned spaces.

The applicable definitions of conditioned and unconditioned spaces as provided by theIECC - 2000 and ASHRAE Standard 90.2 - 1999 are reviewed below as they apply to the

insulation of equipment rooms and in particular the insulation of equipment rooms thatmay be provided with outside air for combustion and ventilation. This review shows thatif the temperature in an equipment room is maintained at 50

oF or above it satisfies

definitions of both the IECC and ASHRAE 90.2 as a conditioned space. TheEngineering Analysis section of this report describes a methodology to calculateequipment room temperatures based on the balance of heat released from the surfaces ofequipment in the room with convective and conductive heat losses from the room.

In addition, ASHRAE 90.2 provides a category of indirectly conditioned space that isdefined in terms of the relative areas and U values of the exterior and interior wallsurfaces and the flow of air between the conditioned space and the indirectly conditioned

space. This definition could be applied with minor modification to equipment roomsprovided with outside air for ventilation.

International Energy Conservation Code 2000 (IECC)

The following four definitions excerpted from the IECC are essential to interpreting thecode requirements for the insulation of equipment rooms. Taken as a whole, thefollowing definitions show that if an equipment room is maintained at 50oF or above, theequipment room is a conditioned space and insulation is not required in the walls, floor orceiling that separate the equipment from other conditioned spaces. Insulation would be

required in the walls and other surface of the equipment room that separate the equipmentfrom the exterior or unconditioned spaces, such as unheated garages or attics.

BUILDING ENVELOPE. The elements of a building which enclose conditionedspaces through which thermal energy is capable of being transferred to or fromthe exterior or to or from spaces exempted from the provisions of Section101.4.1.

CONDITIONED SPACE. A heated or cooled space, or both, within a buildingand, where required, provided with humidification or dehumidification means soas to be capable of maintaining a space condition falling within the comfortenvelope as set forth in ASHRAE 55.

HEATED SPACE. Space within a building which is provided with a positive heatsupply (See Positive heating supply). Finished living space within a basementwith registers or heating devices designed to supply heat to a basement spaceshall automatically define that space as heated space.

POSITIVE HEAT SUPPLY. Heat deliberately supplied to a space by design,such as a supply register, radiator or heating element. Also heat indirectlysupplied to a space through uninsulated surfaces of service water heaters andspace heating components, such as furnaces, boilers and heating and cooling


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distribution systems which continually maintain air temperature within the spaceof 50

oF (10

oC) or higher during normal operation. To be considered exempt from

this definition, such surfaces shall comply with the insulation requirements of thiscode.

The above definitions show that if an equipment space is maintained at 50oF or higher, by

heat indirectly supplied from the surface of service water and space heating systems, itsatisfies the definition of having a Positive Heat Supply. A space with a Positive HeatSupply satisfies the definition of a Heated Space. A Heated Space is Conditioned Spaceand walls between conditioned spaces are not part of the thermal envelope. In this casethe code requires insulating the walls and other surfaces separating the equipment roomfrom the outside or unconditioned spaces since these surfaces are part of the thermalenvelope.

The MECcheck Workbook2also states that, A space is conditioned if heating and/orcooling is deliberately supplied to it or is indirectly supplied through uninsulated surfacesof water or heating equipment or through uninsulated ducts.

ASHRAE Standard 90.2-1993, Energy Efficient Design of Low-Rise Residential

Buildings

As with the IECC, definitions from ASHRAE Standard 90.2 relating to conditionedspaces are reviewed below to provide a basis for interpreting the requirements forinsulating equipment room surfaces. Under Standard 90.2 An equipment room may fallinto one or more of three definitions of the type of space. These are: conditioned space,indirectly conditioned space, and unconditioned space.

An equipment room satisfies the definition of a heated space if, (as with the IECC), theequipment room is maintained at 50F or more at design heating conditions. Theequipment room may also be considered as an indirectly conditioned space based on acomparison of overall exterior and interior heat transfer coefficients. If the equipmentroom is either heated, or indirectly conditioned, then the walls and other surfacesseparating the equipment room from the exterior and other unconditioned spaces wouldrequiring insulation.

If the equipment room is neither heated or indirectly conditioned then the equipmentroom would be an unconditioned space. In this case, the walls and other surfacesseparating the equipment room from other conditioned spaces would require insulation.

2MECcheck TM1998 and 2000 International Energy Conservation Code, Version3.0, April 2000, was developed by the Building Energy Standards Program at PacificNorthwest National Laboratory for use by the U.S. Department of Housing and UrbanDevelopment (HUD) and the Rural Economic and Community Development (RECD)under contract with the U.S. Department of Energy's Office of Codes and Standards. PacificNorthwest National Laboratory is operated by Battelle Memorial Institute for the U.S.Department of Energy under Contract DE-AC06-76RLO 1830.


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ASHRAE Standard 90.2 also makes a distinction between unconditioned spaces and theoutdoor environment with respect to the insulation requirements. The insulationrequirements for surfaces that are exposed to unconditioned spaces are less stringent thanfor surfaces that are exposed directly to the outdoor environment. Therefore, even wherean equipment room is determined to be an unconditioned space, the insulation

requirements applicable to the surfaces separating the conditioned space from theequipment room may be less stringent than for surfaces that are directly exposed to theoutdoor environment.

Excerpts of the applicable definitions from ASHRAE 90.2 are provided below forreference.

CONDITIONED SPACE: cooled space, heated space, or indirectly conditionedspace.

COOLED SPACE: enclosed space within a building that is cooled by a coolingsystem whose sensible capacity exceeds 5 Btu/(h.ft2) or is capable of

maintaining a space dry-bulb temperature of 90F or less at design coolingconditions.

DESIGN HEATING CONDITIONS: winter outdoor design conditions listed forselected locations in chapter 24, table 1, column 5 (97.5 % values) of the 1989

ASHRAE Handbook-Fundamentals.

HEATED SPACE: enclosed space within a building that is heated by a heatingsystem whose output capacity exceeds 10 Btu/(h.ft2) or is capable of maintaininga space dry-bulb temperature of 50F or more at design heating conditions.

INDIRECTLY CONDITIONED SPACE: enclosed space within a building that isnot heated or cooled space, whose area-weighted heat transfer coefficient toheated or cooled space exceeds that to the outdoors or to unconditioned space,or through which air from heated or cooled space is transferred at a rateexceeding three air changes per hour (see heated space and cooled space).

UNCONDITIONED SPACE: space within a building that is not conditioned space(see conditioned space).

UNHEATED SPACE: space within a building that is not heated space (seeheated space).

ENVELOPE COMPONENTS: The requirements shall apply to the envelope ofthe conditioned space including the ceilings, walls, floors over unconditionedspaces, foundations and slabs, doors, fenestration (glazings), partitions betweenconditioned and unconditioned spaces, and air infiltration control.

In comparison, the Standard 90.2 definition of Heated Space is equivalent to the IECCdefinition of Positive Heat Supply. Both definitions rely primarily on performancecriteria, specifically the maintenance of a temperature of 50F or more within theequipment room. Standard 90.2 may also be more stringent since it requires themaintenance of 50F at design heating conditions while the IECC requires the

maintenance of 50F under normal operation which implies more typical exteriorconditions. A problem with both definitions is that they either require the calculation of


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equipment room temperatures based on the thermal characteristics of the proposed designor the measurement of the actual temperatures after the construction is completed. Theimplementation of either of these approaches is complex and time consuming and subjectto interpretation. An engineering methodology for calculating the temperature in anequipment room is provided as part of this report.

In contrast, the definition of Indirectly Conditioned Space provided by Standard 90.2appears to be based on directly stipulated criteria such as the areas and U values of thevarious surfaces that separate the equipment room from the interior and exterior of thebuilding. However the definition as stated in the ASHRAE 90.2 needs both correctionand expansion to serve this purpose. As a correction, and to be consistent with ASHRAEStandard 90.1, the phrase area-weighted heat transfer coefficient should be changed tothe product of U-factor(s) and surface area(s). The definition should be expanded toinclude the thermal effect of outside combustion air that is supplied to the equipmentroom.

An engineering methodology for comparing the overall thermal transmittance from anequipment room to the exterior with the overall thermal transmittance from theequipment room to the interior including the effect of combustion air flow has beenimplemented as a spreadsheet solution and is described in more detail in the EngineeringAnalysis section of this report and in Appendix B.

UNUSUALLY TIGHT CONSTRUCTION

There is an interaction between the gas and energy codes and standards for the ventilationand insulation of gas fired equipment rooms. Energy codes such as the IECC and

standards such as ASHRAE 90.1 and 90.2 require measures to control moisture andreduce infiltration that may result in an unusually tight construction as defined by theInternational Fuel Gas Code (IFGC) and National Fuel Gas Code (NFGC).

The Model Energy Code 1995 Commentary notes that, The code criteria for infiltrationcontrol are such that a building would be of unusually tight construction as determined byNFPA 31, 50, 54. As such, any residence built to the code should provide all air forcombustion of fuels for heating or water-heating equipment from the outdoors or utilizepowered drafts for combustion. This generalization while consistent with the intent ofthe codes is not entirely supported by detailed comparison of related energy and gas codecriteria.

Compliance with energy codes does not necessarily require unusually tight construction.It is possible to comply with energy codes and standards without satisfying the detailedcriteria or general intent of gas code definitions of unusually tight construction. Forexample, both NFGC and IFGC definitions of unusually tight construction require thatwalls and ceilings exposed to the outside have a continuous water vapor retarder.However, vapor retarders are not required by the IECC or ASHRAE Standard 90.2 totighten a building, rather vapor barriers are recommended as a means to prevent


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condensation in unvented building cavities and are specifically not recommended orrequired for construction in hot and humid climates. Therefore a structure without acontinuous water vapor retarder could comply with the energy codes and yet not satisfythe definition of the gas codes of unusually tight construction.

The NFGC and IFGC code definitions of Unusually Tight Construction (UTC) areexcerpted below. Note that both refer to water retarders, weatherstripping windows anddoors and the general use of caulking and sealants at other cracks. The NFGC alsoincludes an average air exchange rate of less than 0.35 air changes per hour as aperformance characteristic of unusually tight construction.

National Fuel Gas Code (1999) Definition of Unusually Tight Construction

Unusually Tight Construction. Construction where (1) walls and ceilingsexposed to the outside atmosphere have a continuous water vapor retarder witha rating of one perm (6 x 10-11kg/pa-sec-m2) or less with openings gasketed or

sealed; and (2) weather stripping has been added on operable windows anddoors; and (3) caulking or sealants are applied to areas such as joints aroundwindows and door frames, between sole plates and floors, between wall-ceiling

joints, between wall panels, at penetrations for plumbing, electrical, and gaslines, and at other openings; and (4) the building has an average air infiltrationrate of less than 0.35 air changes per hour.

Section 5.3.2 states that, equipment located in buildings of unusually tight constructionshall be provided with air for combustion, ventilation, and dilution of flue gasses usingthe methods described in 5.3.3, 5.3.4, or 5.3.5. However, 5.3.3(a) allows all air frominside the building. This is presumed to be in error since the intent of the code withrespect to unusually tight construction is to require all air from outdoors using the

methods described in 5.3.3(b), 5.3.4, and 5.3.5. This suggested correction maintainsconsistency with the 1996 edition of the NFGC and the 2000 Edition of the IFGC. It mayalso be noted that the 1999 edition of the NFGC adds section 5.3.3(c) which allows acombination of air from indoors and outdoors where the building is not of an unusuallytight construction.

International Fuel Gas Code (2000) Definition of Unusually Tight Construction

Unusually Tight Construction. Construction meeting the followingrequirements:

1. Walls and ceilings exposed to the outside atmosphere having acontinuous water vapor retarder with a rating of 1 perm (57 ng/s-m2-Pa) orless with openings gasketed or sealed; and2. Storm windows or weatherstripping on operable windows and doors; and3. Caulking or sealants applied to areas, such as joints around window anddoor frames, between wall-ceiling joints, between wall panels, atpenetrations for plumbing, electrical and gas lines, and at other openings


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Additional related excerpts of the IECC 2000, ASHRAE Standard 90.2 and ASHRAEStandard 62 are included with commentary in Appendix A to provide a directexamination of how energy and ventilation codes and standards are related to the gascode definitions of unusually tight construction.

As summarized below, a review of related gas and energy provisions finds that a housebuilt in compliance with the requirements and recommendations of the energy codes andstandards does not necessarily satisfy the definitions of unusually tight construction.Also, the specific criteria of the gas and energy codes are not always directly comparablewith energy requirements. It is also noted that overly tight construction with less than0.35 air changes per hour (a criterion of the NFGC) would also fail to satisfy theminimum ventilation rate required by ASHRAE Standard 62.

Continuous Water Vapor Retarder: Both the National and International Fuel Gas Codesrefer to a continuous water vapor retarder with a rating of 1 Perm or less. This implies acontinuous sheet of material as compared to the discontinuous barrier typically provided

with the installation of batt insulation applied between the studs of standard wallconstruction. Also, water vapor retarder should not be confused with permeable whole-house wrap (see below) commonly used in new construction as a water barrier and toreduce infiltration. The primary purpose of a vapor retarder is to prevent condensation inunvented cavities of frame walls, floors and ceilings that can facilitate the growth of moldmildew and rot. Both the International Energy Code and the ASHRAE Standard 90.2recommend the use of vapor retarders except in hot and humid climates.

Vapor Permeable Whole-House Wrap: Although the use of a whole-house wrapcontributes significantly to tightness, the gas code criteria for UTC does not apply sincethe permeability of the wrap is greater than 1 perm. The use of a moisture vapor-

permeable whole-house wrap is recommend by both the IECC and ASHRAE 90.2 toreduce infiltration and increase the tightness of the construction. The house wrap isapplied at the exterior of the construction and ideally it should have a permeability that isgreater than any membranes or materials used at the interior of the wall construction.This approach ensures that the wrap reduces infiltration without impeding the flow ofvapor that might cause condensation. It is not uncommon for residential construction touse a permeable whole house wrap at the exterior of the construction without a

continuous water vapor retarder.

Windows and Doors: Gas and energy code criteria for the tightness of windows anddoors are not directly comparable. Storm windows or weatherstripping on windows and

door are easily recognized characteristics of UTC as defined by the NFGC and IFGC. Incontrast, the IECC and ASHRAE Standard 90.2 specify widow and door air tightnesswith maximum leakage rates in either cfm per length of crack or cfm per square foot ofarea. Weather stripping is specified for site-built doors and windows but storm windowsare not referred to by energy codes or standards. Also most windows in currentconstruction are weatherstripped with sealed multiple-pane construction rather thanremovable storm windows.


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Caulking and Sealants: Caulking and sealants are recommended by the energy codes andstandards. There is little ambiguity in these requirements relative the gas code definitionsof unusually tight construction. However, moisture vapor permeable house wrap may, inpart, be an alternative to other caulking or sealants.

Average Air Infiltration Rate: The NFGC includes an additional criterion referring to anaverage air infiltration rate of less than 0.35 air changes per hour. While the generalweatherstripping, caulking and sealants criteria refer to directly observable characteristicof the construction, the average air change rate is a performance criterion that is difficultaccurately measure or predict. In addition, the NFGC does not specify a measurementprocedure, or the time period for averaging or weather conditions that should be includedin the measurement or calculation of the average air changes per hour.

It should also be noted that a house with less than 0.35 air changes per hour of outside airventilation probably does not comply with ASHRAE Standard 62-1999, Ventilation forAcceptable Indoor Air Quality. As presented on Table 2 of this standard, residential

living areas should have a minimum of 0.36 ach or not less than 15 cfm (7.5 L/s) perperson. It is also noted on Table 2 that, ventilation is normally satisfied by infiltrationand natural ventilation. On the other hand ASHRAE 90.1 warns that

The requirements (of 90.1) are not intended to be used to adversely impactindoor air quality. They are not deemed to supply adequate air supply forcombustion and ventilation or provide adequate fresh air supply. Considerationof uses other than reducing unwanted air leakage is not covered in this standard.

The goal of this report is similarly limited to consideration to the energy costs associatedwith infiltration when air from inside or outside the buildings is used for combustion andventilation. Issues of how the gas and energy codes could be structured to allow designs

that satisfy ventilation and combustion air requirements without conflict or unnecessarycost are outside the scope of this study. This study simply presents energy costsassociated with several obvious interpretations of the existing codes.

INFILTRATION AND VENTILATION

Appendix A provides a review of the IECC and ASHRAE Standards related infiltrationand ventilation. Similarities and differences related to the treatment of infiltration andventilation as presented in various codes and standards are discussed therein. ThisAppendix also provides a review and excerpts of the energy codes and standards related

to gas code definitions of unusually tight construction.


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ENGINEERING ANALYSIS

This section presents an engineering analysis of equipment room temperatures energyconsumption and costs associated with providing outside air for combustion andventilation and adding insulation to walls and other surfaces that separate equipment

rooms from conditioned spaces. Additional details about the analysis are provided inAppendix B, Model User Instructions and Documentation.

OVERVIEW OF METHODOLOGY

The engineering analysis employs a steady-state assumption and solves for the equipmentroom temperature required to balance the total flow of energy into and out of theequipment room. Heat energy flows into the equipment room from the surfaces of gas-fired equipment and through walls and other surfaces adjoining warmer conditionedspaces. Heat energy flows out of the equipment room through exterior walls. Heat

energy is also transported by convection associated with air flows into the equipmentroom from the conditioned space and from outside, particularly when equipment room isdirectly vented to the outside to provide combustion air. It is assumed that all the airentering the equipment room exits via the vent system of the gas fired equipment. Thispattern if air flow is consistent with the use of a single outside vent.

A variety of gas fired equipment and equipment room configurations has been analyzed.The equipment room was assumed to be a confined space located in the interior of thehouse with a well insulated ceiling/roof exposed to the exterior and the remaining wallsand floor adjoining other conditioned spaces. The net thermal effect of the equipmentroom on the heating and cooling loads of the residence are analyzed for three variations

of insulation placement and combustion air source.

Uninsulated interior surfaces with all combustion air from the conditionedspace

Uninsulated interior surfaces with all combustion air from outside

Insulated interior wall and floor with all combustion air from outside

The net thermal effect of the equipment room on the heating and cooling costs of theconditioned space includes thermal conduction through adjoining walls and increases ininfiltration to the conditioned space associated with the use of air from the conditionedspace for combustion. The comparison of energy use for these three cases provides thebasis for evaluating the benefits and costs of adding insulation to interior surfaces andusing outdoor air for combustion and ventilation.

Six variations of gas fired equipment were considered as follows:

Mid-efficiency water heater with conventional draft hood vent system

Side-wall vent water heater using room air for combustion


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High-efficiency water heater with fan assisted draft

Mid-efficiency furnace with fan assisted draft

High-efficiency furnace with fan assisted side-wall vent

The combination of a mid-efficiency water heater and furnace

The performance of the various equipment and equipment room configurations wasevaluated for climate data from six U.S. cities including:

Atlanta, Georgia

Baltimore, Maryland

Chicago, Illinois

Houston, Texas

Seattle, Washington.

SUMMARY OF ENERGY ANALYSIS RESULTS

The results for a variety of equipment combinations and climate data show thattemperatures in equipment rooms with outside combustion air are maintained above 50oFin most cases. Equipment room temperatures below 50oF were calculated only with theside-wall vent water heater for the outdoor design heating temperatures of Baltimore andChicago. This is because the side-wall vent water heater considered in this analysis usesa large quantity of outside for the dilution and cooling of the flue gas to allow sidewallventing. A temperature of greater than 50oF was maintained for all the other equipmentconfigurations and climate data that were evaluated.

The maintenance of equipment room temperatures at or above 50oF is an important code

criterion allowing the equipment room to be considered as a conditioned space that neednot be insulated from other conditioned spaces. For example, the analysis shows that anequipment room with a mid-efficiency fan-assisted draft furnace and a draft hood waterheater maintains a temperature above 50

oF with outdoor temperatures as low as -12

oF.

This is for an equipment room with well-insulated exterior walls, uninsulated interiorwalls and combustion air from outside. Figure1 illustrates the temperatures and balanceof heat flows for this example.


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The figure shows a total heat release from the equipment, in this case a mid-efficiencywater heater and furnace, of 2025 Btu/hr. Because the temperature of the equipmentroom, at 50.3oF, is cooler that the adjoining 70oF conditioned space, the total heat gain tothe equipment room includes an additional 1047 Btu/hr for a total heat gain of 3072Btu/hr, which balances the total heat loss. This figure also shows that most of the airflow into the equipment room is from the outside at a rate of 48.8 cfm with some

infiltration from the conditioned space at a rate of 2.3 cfm. The analysis assumes that theair flow from the conditioned space to the equipment room causes small net increase of1.17 cfm to the total outside air infiltration into the conditioned space.3

Estimates of seasonal energy consumption use a modified bin-temperature method4tocalculate the impact of the equipment room on the heating and cooling loads of theadjoining conditioned spaces. For comparison, the analysis is repeated assumingcombustion air from the conditioned space and combustion air from outside both withand without insulation in the walls and other surfaces separating the equipment roomfrom conditioned spaces. In all cases, it is assumed that the exterior surfaces of theequipment room were insulated.

3It is assumed that air flow from a conditioned space to an equipment room isbalanced in equal parts by a net increase in infiltration to the conditioned space and a netreduction in exfiltration by other leakage paths from the conditioned space to the exterior.Thus the net gain in infiltration to the conditioned space is assumed to be equal to half theflow rate of air from the conditioned space to an equipment room.

4See ASHRAE Fundamentals, Chapter 28.

On-Cycle Temperatures and Heat Flows

Conditioned Space Equipment Space Exterior

70 oF 50.3 oF -12 oF

1,047 Btu/hr 3,072 Btu/hr

45 Btu/hr On-Cycle

Equip. Heat Gain2025

Btu/hr1.17 cfm 2.3 cfm 48.8 cfm

Scenario 17: Mid. Eff. Water Heater and Furnace, outside air, uninsulated

Figure 1. Equipment Room Temperature and Thermal Balance


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Table 1 summarizes the annual savings or cost for the addition of insulation forequipment rooms provided with combustion air from outside. The table provides resultsfor six configurations of gas-fired equipment and weather data from five cities. Increasedannual energy costs are shown as negative numbers indicated by parenthesis.

As shown by the table, the addition of insulation to the interior walls of equipment roomsincreases energy consumption and operating costs for 20 out of the 30 combinations ofequipment and climate. For these combinations the additional insulation reduces the flowof useful heat from the equipment room to conditioned spaces during the heating season.Note that the addition of insulation to equipment rooms with mid or high-efficiencyfurnaces increases energy costs for all cities and in particular for Seattle, which has aprolonged, but generally mild, heating season.

Table 1. Annual Energy Savings/Costs for Additional Insulation

Equipment Room Description Atlanta Baltimore Chicago Houston SeattleMid-efficiency water heater $0.87 $0.54 $0.60 $3.08 $(2.74)

Side-wall vent water heater $0.34 $0.28 $0.32 $0.99 $(0.72)

High-efficiency water heater $(0.07) $(0.17) $(0.22) $0.21 $(0.52)

Mid-efficiency furnace $(3.49) $(3.38) $(2.40) $(2.56) $(6.87)

High-efficiency furnace $(1.57) $(1.25) $(0.54) $(1.24) $(3.30)

Mid-efficiency water heater and furnace $(2.22) $(2.21) $(0.88) $1.02 $(9.49)

Energy costs are reduced by the addition of insulation in only 10 of the thirtycombinations of equipment and climate shown on the table. Energy cost savings arenoted for equipment room with a mid-efficiency or side-wall vent water heaters for all

cities except Seattle. Energy cost savings are also noted for the climate of Houston forseveral types of water heaters and for the combination of a mid-efficiency water heaterand furnace.

Additional insulation saves energy primarily during the cooling season by reducing theflow of heat from the equipment room to conditioned spaces. For those combinations ofequipment and climate where additional insulation provides some energy cost savings,the cost savings are small. It appears that insulating the walls between the equipmentroom and the conditioned space may be justified in climates dominated by cooling loads.In this case, locating water heater outside the thermal envelope in an unconditioned spacesuch as a well-ventilated garage or attached shed should be considered. However, it is

more energy efficient to locate furnaces within the thermal envelope for all the climatedata considered in this study.

Table 2 summarizes the benefits and costs associated with providing confined equipmentrooms with outside air for combustion and ventilation as compared to the use of air fromthe conditioned space. Energy cost savings are shown as positive numbers whileincreased annual energy costs are shown as negative numbers indicated by parenthesis.


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The results are for equipment rooms with uninsulated interior walls. As shown by thetable, the use of outside air increases annual energy costs in most cases.

The table shows that the use of outside air for combustion increases total heating andcooling costs in most cases. Some savings are achieved for the use of outside with side-

wall vent water heaters in Atlanta, Baltimore and for all water heaters in Houston. In allother cases the use of outside air for combustion increases energy costs compared to theuse of air from the conditioned space.

Table 2. Annual Energy Benefits and Costs for Outside Combustion Air

Equipment Room Description Atlanta Baltimore Chicago Houston Seattle

Mid-efficiency water heater $(0.62) $(2.93) $(5.03) $3.91 $(5.15)Side-wall vent water heater $0.73 $0.28 $(0.17) $2.15 $(0.50)High-efficiency water heater $(0.13) $(0.32) $(0.50) $0.22 $(0.49)Mid-efficiency furnace $(0.55) $(0.91) $(1.17) $(0.09) $(1.10)

High-efficiency furnace $(0.91) $(1.43) $(1.72) $(0.33) $(1.64)Mid. Eff. Water Heater and Furnace $0.41 $(1.51) $(3.54) $4.73 $(3.71)

While it is true that the use of air from the conditioned space for combustion increasesheating and cooling loads, the alternative of providing outside air to a confinedequipment space is not without energy costs. The use of outside air reduces thetemperature in the equipment room and on average may reduce the useful flow of heatfrom an equipment room to the occupied space during the heating season. In effect, theuse of indoor air for combustion enhances the recovery of heat from the surfaces of thegas fired equipment while the use of outdoor air tends to vent the heat from the surfacesof equipment to the outside.

The use of indoor air for combustion increases the temperature in the equipment roomand increases the useful heat flow from the equipment room to the conditioned spaceduring the heating season. The gain in heat flow through the uninsulated walls of theconfined equipment space to the conditioned space provides a net benefit in most cases.Exceptions include the cooling load dominated climate of Houston and side-wall ventwater heaters that use relatively high volumes of outside air.

In summary, the findings of the analysis can be stated as three generalizations:

Equipment rooms provided with outside air for combustion and ventilationwill maintain a temperature above 50oF at the outside design heatingtemperature of most climates and for most common type of gas-firedequipment.

Adding insulation to the walls and other surfaces that separate a ventilatedequipment room from adjoining conditioned spaces will increase annualenergy costs in most cases except for water heaters in cooling dominatedclimates


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The use of outside air for combustion and ventilation of confined equipment

rooms does not reduce energy consumption relative to the use of air from theconditioned space except in climates dominated by cooling loads.

SCENARIO DEVELOPMENT

This section provides a detailed development of the types of equipment and equipmentroom configurations that have been considered. Detailed equipment characteristics arealso provided here.

Six combinations of space heating and water heating equipment were considered forfurther analysis. For each type or combination of equipment, heating and cooling loadshave been evaluated for three cases:

1. combustion air from the conditioned space provided to an equipment room,

2. combustion air from outside provided to an equipment room,3. the equipment room provided with exterior levels of insulation for surfaces

and doors adjoining conditioned spaces.

It is assumed for all cases that the exterior surfaces of the any equipment space areprovided with exterior levels of insulation. This analysis has been repeated with weatherdata for five locations including Atlanta, Chicago, Houston, Seattle and Baltimore.

Water Heater Categories

Four types of water heaters were considered for further study. These are: (1) olderstandard-efficiency water heaters, (2)mid-efficiency water heaters, (3)side-wall ventwater heaters and; (4)high-efficiency water heaters.

Older standard-efficiency units typically having an energy factor of less than 50% weredesigned to operate with relatively high rates of excess combustion air. Relatively few ofthese systems are remaining in service. No further consideration of standard-efficiencywater heaters is included in this report.

Mid-efficiency water heaters, having and an efficiency factor of approximately 57%, arecharacteristic of typical new water heaters. Recovery efficiency is improved and standby

losses are reduced relative to older standard-efficiency water heaters within theconstraints of the same basic reliable natural draft design. This type of water heater isanalyzed by itself and combined in an equipment with a mid-efficiency furnace.

Side-wall vent water heaters are essentially equivalent to the conventional mid-efficiencywater heaters, having and efficiency factor of approximately 57%, but with the additionof a power vent fan providing increased dilution air during the on-cycle to allow the useof low-temperature plastics pipe with sidewall venting. Note that the dilution air required


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by the fan must be provided with the combustion air required by this type of water heater.Further analysis of this type of water heater investigates the impact of its increased totalair requirements There are similar design water heaters using ducted outside air toprovide both the combustion and dilution air required by the system. This type of sealed-combustion system is outside the scope of this study.

High-efficiency water heaters having an efficiency factor of 65% or better use a smallinduced draft fan to assist the venting of relatively cool (near condensing) flue gasseswithout additional dilution air. This approach can provide improved efficiency but it hasnot been widely accepted. The total air requirement for this type of appliance isminimized with low excess air and the elimination of dilution air. Further analysis ofhigh-efficiency, fan assisted water heaters has been done to investigate the impact of theirreduced total air flow requirements.

Furnace and Space Heating Equipment Categories

Three types of gas-fired space heating systems were considered for further analysis:

1. Standard-efficiency systems characteristic of existing gravity vented systemswith draft diverters,

2. Mid-efficiency systems using a fan assisted draft with normal venting and;

3. High-efficiency systems with the side-wall power venting of vent gasses atnear-condensing temperatures.

These three types, with nominal AFUE efficiencies of 70%, 80% and 90% respectively,characterize the range of available equipment. Also the characteristics of these furnace

categories nearly match the characteristics of comparable boilers and may be consideredas representing boilers as well as furnaces.

Standard-efficiency, gravity-vent, space heating systems were not considered for furtheranalysis in this report since they are most likely to be found in existing residences thatare not overly tight. Mid-efficiency furnaces were considered as a more representativetype of heating system. The further analysis of this type of system combined in anequipment space with a mid-efficiency type water heater is also included.

Further analysis of a high-efficiency furnace is included. However, combinations ofhigh-efficiency furnaces with mid-efficiency or high-efficiency water heaters are notincluded at this time as a means to limit the total number of scenarios to six equipmentconfigurations.

Equipment Room Thermal Characteristics


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Table 3 shows the thermal properties, R values, and U values for the materials andsurfaces of the equipment room. Insulation levels have been selected to meet or exceedcode requirements for the exterior surfaces of the equipment room. Interior surfacesincluding walls, floor and a door are analyzed with and without insulation. Equipmentroom configurations containing a single water heater or furnace assume an interior room

with a 3 foot by 3 foot floor area with an exterior ceiling and all other surfaces adjoiningconditioned spaces. Equipment room configurations containing both a water heater and afurnace assume a room with a 3 foot by 6 foot floor area with an exterior ceiling and one3-foor exterior wall. The equipment room has an insulated metal door with an insulatedU value of 0.35 Btuh/ft2or an uninsulated hollow core wood door with a U value of 0.46Btuh/ft.2

Table 3. Equipment Room Thermal Properties

Thermal Properties ofMaterials and Components

InteriorWall

InsulatedInterior

Wall

InsulatedExterior

Wall

InsulatedCeiling

InteriorFloor

InsulatedFloor

Outside surface 0.68 0.68 0.17 0.61 0.92 0.92Wood beveled lap siding 0.81Insulated foam sheathing 4.000.5" GWB 0.45 0.45Plywood 3/4" 0.93 0.93Wall or floor cavity 0.85 1.00 1.00Mineral fiber batt insulation 13.00 13.00 21.00Loose fill insulation 38.000.5" GWB 0.45 0.45 0.45 0.45 0.45 0.45interior surface 0.68 0.68 0.68 0.61 0.92 0.92

R-values 3.11 15.26 19.11 39.67 4.22 25.22

U-Values 0.322 0.066 0.052 0.025 0.237 0.040

Appliance Characteristics

Table 4 summarizes the characteristics of four types of water heaters and three types offurnaces considered to represent the range of existing and current high efficiencyequipment. For each listed appliance type, the table provides the nominal capacity and


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Table 4. Equipment Characteristics and Combinations Considered for Further Study

Notes Description Capacity Efficiency Vent type Ex

Water Heaters Btu/hr Recovery EF Standby

1,2 Standard-eff. water heater 35,000 70% 50.0% 2.0% draft hood 3 Mid-efficiency water heater 35,000 78% 57.0% 1.5% draft hood

3,4 Side-wall vent water heater 35,000 78% 57.0% 1.0% power vent (side wall) 3,5 High-efficiency water heater 35,000 84% 65.0% 0.5% power vent (side wall)

Surface Losses

Furnaces Btu/hr AFUE On-cycle Off-cycle

2 Standard-eff. furnace 100,000 70% 2.5% 1.0% draft diverter 3 Mid-efficiency furnace 100,000 80% 2.0% 0.0% fan assisted gravity vent 3 High-efficiency furnace 100,000 90% 1.0% 0.0% power vent (side wall)

3 Mid-efficient water heater and furnace

6 Mid-efficient water heater, high-efficiency furnace7 High-efficiency water heater and furnaceNotes

1 Not recommended for further analysis

2 Standard-efficiency water heaters and furnaces are becoming rare and are unlikely to be located in hous

3 Recommended for further analysis of scenarios and weather data.4 This mid-efficiency side-wall water heater uses significant dilution air to allow a plastic

sidewall vent5 High-efficiency (greater than 85% recovery efficiency) water heaters are relatively rare although they pres

this analysis.6 Mid-efficiency and high-efficiency furnaces are significantly different in combustion air requirements. Not

analysis in this study.7 This configuration is not recommended for detailed analysis because of the relative rarity of very high effi

water heaters.


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efficiency. For water heaters, the nominal efficiency is listed in terms of energy factor andrecovery efficiency. For furnace efficiency the AFUE value is listed. Estimated off-cycle lossesare listed for water heaters, and for boilers, both on-cycle and off-cycle losses are listed. Theseon-cycle and off-cycle losses represent the heat release from the appliances and venting that goesdirectly to the equipment room expressed as a percentage of the heating capacity.

The table continues with the vent type, being either gravity vent with a draft hood or diverter orbeing fan assisted. Excess air is shown as a percentage of the stoichiometric minimum airrequirement which is approximately 10 ft3per 1000 Btu/hr input capacity for all types of gas-fired appliances. In general, minimizing excess air is associated with increased combustionefficiency. However, with minimum excess air, problems of incomplete combustion andcondensation are more likely.

Dilution air is shown as a percentage of the total combustion and excess air. Off-cycle dilutionair flow is estimated to be 30% of the on-cycle flow as a conservative value (tending to increaseenergy use). Dilution air may also be used by side-wall vent water to cool the products of

combustion to allow sidewall venting using plastic pipe.

The analysis has shown that the results are sensitive to assumed values of combustion anddilution air requirements and the rate of heat release from appliance surfaces to the equipmentspace during both on and off cycles of operation. The equipment characteristics as shown on thetable represent engineering estimates for typical types of equipment rather than data for specificmanufacturer or model of equipment. Some of the data required for this analysis is not readilyavailable from manufacturers or other testing organizations in particular, on-cycle and off-cycleair flow rates and standby or surface losses. On-cycle and off-cycle air flow rates are alsotreated as constants as a simplifying assumption for this analysis although it is understood thatactual rates vary as a function of stack characteristics and local weather conditions particularly

for natural draft system. However the six equipment configurations considered in this analysiswere developed to provide a range of reasonable values that taken as a whole is intended toprovide an unbiased characterization of typical residential gas-fired equipment.

Climate Data

Five cities were selected as sources of climate data for further analysis. They are: Atlanta,Baltimore, Chicago, Houston and Seattle. BinMaker software from InterEnergy Software Inc.

5

was used as the source of climate data for this analysis. Table 4 provides a summary of averageJanuary temperatures and ASHRAE winter design temperatures for the five selected cities.

ASHRAE design temperatures are provided for 99.6% and 99% percentiles indicating thepercentage of time that temperatures are above the design values. The 99th percentile values areused to evaluate the equipment room temperatures at design heating conditions below.

5A joint venture of GRI and IGT/SMP, 8600 West Bryn Mawr Avenue, Chicago, IL,January 1999. This program provides summaries of TMY-2 files.


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Table 5. Average January and ASHRAE Heating Design

Temperatures

City Heating Cooling Average January ASHRAE Heating Design

Degree Days(65)

Degree Days(65)

Temperature 99.6% 99%

Atlanta 2991 1667 40.8 18 23

Chicago 4707 1137 24.1 -6 -1

Baltimore 6176 940 30.9 11 15

Houston 1371 3012 53.7 29 34

Seattle 4611 167 40.0 23 28

Energy Costs

To simplify the analysis and facilitate comparisons, the same electrical energy and gas costs are

assumed for all the cases in this analysis. These costs are:

Natural Gas $1.00 per Therm

Electrical Energy $0.10 per kWh

This simplified cost basis provides a reasonable basis for the comparisons and conclusions in thisreport and can be easily adjusted as necessary where actual costs are known. Similarly thecooling system efficiency is assumed to be 10 SEER which provide a reasonable basis forexisting systems and can be easily adjusted as necessary to consider the effect of new moreefficient systems.

EQUIPMENT ROOM TEMPERATURES AND ANNUAL ENERGY COSTS FOR SIX

CITIES

This section provides the detailed results of the analysis of equipment room temperatures and

energy use for climate data from six cities. Detailed data is presented in two tables for each city.

1. Equipment Room Design Heating Temperatures

2. Annual Energy Costs

TheEquipment Room Design Heating Temperatures tables show the equipment room

temperatures during on-cycles and off cycles for each of the six equipment configurations.These tables also show the temperature in the conditioned space and the ASHRAE 99% designheating temperature outside. A review of these temperature data for each of the six cities showsthat equipment room temperatures are maintained above 50 oF except for sidewall vent heaters inChicago and Baltimore.

TheAnnual Energy Cost Tablesprovide a detailed summary of annual energy costs with aseparate table for each city. Each table shows impact of equipment room insulation and


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ventilation on the heating and cooling cost of the conditioned space. Energy cost savings areshown as negative numbers indicated by parenthesis.

The three variations of equipment space insulation and ventilation include (1) inside combustionair with uninsulated interior walls, (2) outside combustion air with uninsulated interior walls and

(3) outside combustion air with insulated interior walls. For each of these three variations, thetables show the energy cost for six combinations of gas-fired equipment.

However it important to keep in mind that the analysis was designed to evaluate the effect ofchanges in insulation and the source of combustion air not to provide a comparison of differenttypes or efficiencies of equipment. The tables do not show the total cost of energy consumed bythe equipment but rather only the energy costs associated with the equipment room.

For example, Table 8 shows the annual heating, cooling and total energy costs for Baltimore.The results of this table show that the addition of insulation and the use of outside air forcombustion increases the cost of operation by reducing useful heat gains from the equipment

room. The first three rows of this table show the energy costs associated with three variation ofinsulation and ventilation for an equipment room containing a mid-efficiency water heater. Withindoor combustion air and no insulation the equipment room provides a net reduction in heatingcost of $9.41 and a net increase in cooling cost of $8.64 for a net total cost savings of $0.77. Anet cost savings is provided because the net heat gain from the equipment room to theconditioned space exceeds the additional infiltration losses from the use interior air forcombustion. Cooling energy costs are increased both be heat transfer through adjoining wallsand increases in infiltration. In comparison, an equipment room, with insulated interior wallsand outside combustion air, provides a net reduction in heating cost of $3.07 and a net increasein cooling cost of $4.81 for a total cost increase of $1.74. Thus the combination of insulationand outside combustion air increase the cost of heating and cooling the conditioned space

because they reduce beneficial heat gains to the conditioned space.

Again referring to Table 8, the result of this table will be used to show that although a moreefficient furnace will reduce total heating costs, the heating and cooling costs associated with theequipment room may increase. This will occur if the characteristics of the more efficient furnaceresult in a reduction of the temperature in the equipment room. As shown by the table anequipment room with a mid-efficiency furnace using outside air and having uninsulated interior

walls reduces total heating and cooling costs by $5.90 while a comparable equipment room witha high-efficiency furnace reduces total heating and cooling costs by only $1.90. The moreefficient furnace increases the cost of operation associated with the equipment room. However,as shown by Table 7, the on-cycle temperature in the equipment room is reduced from 67.9

oF to

64.2o

F by changing from a mid-efficiency furnace to a high-efficiency furnace. The reduction inequipment room temperatures reduces the net heat gain to the conditioned space during theheating season.

A detailed examination of the analysis was made to investigate how the total cost of operationcould be increased by the use of a more efficient furnace. This examination showed that theequipment characteristics used in the analysis assume a reduction (from 2% to 1% of capacity)in the rate of heat loss from the surface of the high-efficiency furnace compared to the mid-


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efficiency furnace. The reduction equipment heat loss is responsible for the reduced equipmentroom temperatures. Excess air was also reduced from 30% to 20% for the high-efficiencyfurnace relative to the mid-efficiency furnace. This reduction in air flow that would tend toincrease equipment room temperatures. However, in this case, the reduction in equipment losseswas more significant than the reduction of air flow. The above example shows the sensitivity of

the analysis to the heat losses from the surfaces of equipment and venting systems.


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Atlanta

Table 6. Equipment Room Design Heating Temperatures -- Atlanta

Inside Outside Equipment RoomEquipment Room Description Conditioned

SpaceHeatingDesign

On-cycle Off-cycle

Mid-efficiency water heater, outside air,uninsulated

70.0 23.0 63.2 67.7

Side-wall vent water heater, outside air,uninsulated

70.0 23.0 53.5 78.2

High-efficiency water heater, outsideair, uninsulated

70.0 23.0 69.5 74.3

Mid-efficiency furnace, outside air,

uninsulated

70.0 23.0 71.4 69.0

High-efficiency furnace, outside air,uninsulated

70.0 23.0 67.5 69.1

Mid. Eff. Water Heater and Furnace,outside air, uninsulated

70.0 23.0 66.5 66.5

Table 7. Annual Energy Costs -- Atlanta

Equipment Room Description Heating Cooling TotalMid-efficiency water heater, inside air, uninsulated $(9.31) $11.97 $2.65Mid-efficiency water heater, outside air, uninsulated $(6.15) $9.42 $3.28Mid-efficiency water heater, outside air, insulated $(4.22) $6.64 $2.41

Side-wall vent water heater, inside air, uninsulated $(16.96) $11.59 $(5.37)Side-wall vent water heater, outside air, uninsulated $(16.67) $10.57 $(6.10)Side-wall vent water heater, outside air, insulated $(16.16) $9.71 $(6.44)

High-efficiency water heater, inside air, uninsulated $(10.06) $5.88 $(4.18)High-efficiency water heater, outside air, uninsulated $(9.76) $5.71 $(4.05)High-efficiency water heater, outside air insulated $(9.41) $5.43 $(3.98)

Mid-efficiency furnace, inside air, uninsulated $(7.27) $0.21 $(7.06)Mid-efficiency furnace, outside air, uninsulated $(6.59) $0.07 $(6.51)

Mid-efficiency furnace, outside air, insulated $(3.10) $0.07 $(3.03)High-efficiency furnace, inside air, uninsulated $(3.91) $0.18 $(3.73)High-efficiency furnace, outside air, uninsulated $(2.89) $0.06 $(2.82)High-efficiency furnace, outside air, insulated $(1.31) $0.06 $(1.25)

Mid. Eff. Water Heater and Furnace, inside air, uninsulated $(13.38) $12.39 $(0.99)Mid. Eff. Water Heater and Furnace, outside air, uninsulated $(11.12) $9.71 $(1.40)Mid. Eff. Water Heater and Furnace, outside air, insulated $(5.82) $6.63 $0.81


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Baltimore

Table 8. Equipment Room Design Heating Temperatures -- Baltimore

Inside Outside Equipment RoomEquipment Room Description ConditionedSpace

HeatingDesign

On-cycle Off-cycle


70.0 15.0 60.5 66.0


70.0 15.0 49.5 78.0


70.0 15.0 68.1 74.2

Mid-efficiency furnace, outside air,uninsulated

70.0 15.0 67.8 68.8


70.0 15.0 64.3 68.9


70.0 15.0 62.4 64.8

Table 9. Annual Energy Costs -- Baltimore

Equipment Room Description Heating Cooling Total

Mid-efficiency water heater, inside air, uninsulated $(9.40) $8.73 $(0.66)Mid-efficiency water heater, outside air, uninsulated $(4.74) $7.00 $2.26Mid-efficiency water heater, outside air, insulated $(3.20) $4.93 $1.72



Mid-efficiency furnace, inside air, uninsulated $(6.92) $0.16 $(6.76)Mid-efficiency furnace, outside air, uninsulated $(5.91) $0.06 $(5.84)Mid-efficiency furnace, outside air, insulated $(2.53) $0.06 $(2.46)

High-efficiency furnace, inside air, uninsulated $(3.31) $0.13 $(3.18)High-efficiency furnace, outside air, uninsulated $(1.81) $0.06 $(1.75)High-efficiency furnace, outside air, insulated $(0.55) $0.05 $(0.50)

Mid. Eff. Water Heater and Furnace, inside air, uninsulated $(12.14) $9.06 $(3.08)Mid. Eff. Water Heater and Furnace, outside air, uninsulated $(8.80) $7.23 $(1.57)Mid. Eff. Water Heater and Furnace, outside air, insulated $(4.30) $4.94 $0.64


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Chicago

Table 10. Equipment Room Design Heating Temperatures -- Chicago


SpaceHeatingDesign

On-cycle Off-cycle

Mid-efficiency water heater,outside air, uninsulated

70.0 15.0 60.5 66.0

Side-wall vent water heater,outside air, uninsulated

70.0 15.0 49.5 78.0

High-efficiency water heater,outside air, uninsulated

70.0 15.0 68.1 74.2

Mid-efficiency furnace,

outside air, uninsulated

70.0 15.0 67.8 68.8

High-efficiency furnace,outside air, uninsulated

70.0 -1.0 57.9 68.6


70.0 -1.0 54.2 61.6

Table 11. Annual Energy Costs -- Chicago

Equipment Room Description Heating Cooling TotalMid-efficiency water heater, inside air, uninsulated $(8.71) $6.19 $(2.53)Mid-efficiency water heater, outside air, uninsulated $(2.80) $5.30 $2.50Mid-efficiency water heater, outside air, insulated $(1.82) $3.73 $1.90



Mid-efficiency furnace, inside air, uninsulated $(4.62) $0.09 $(4.54)Mid-efficiency furnace, outside air, uninsulated $(3.41) $0.04 $(3.37)

Mid-efficiency furnace, outside air, insulated $(1.01) $0.04 $(0.97)High-efficiency furnace, inside air, uninsulated $(1.64) $0.07 $(1.57)High-efficiency furnace, outside air, uninsulated $0.12 $0.04 $0.16High-efficiency furnace, outside air, insulated $0.66 $0.04 $0.69

Mid. Eff. Water Heater and Furnace, inside air, uninsulated $(8.85) $6.40 $(2.45)Mid. Eff. Water Heater and Furnace, outside air, uninsulated $(4.38) $5.47 $1.09Mid. Eff. Water Heater and Furnace, outside air, insulated $(1.75) $3.73 $1.97


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Houston

Table 12. Equipment Room Design Heating Temperatures -- Houston


SpaceHeatingDesign

On-cycle Off-cycle


70.0 28.0 64.9 68.7


70.0 28.0 56.0 78.4


70.0 28.0 70.4 74.4

Mid-efficiency furnace, outside air,uninsulated

70.0 28.0 73.6 69.1


70.0 28.0 69.5 69.2


70.0 28.0 69.0 67.5

Table 13. Annual Energy Costs -- Houston

Equipment Room Description Heating Cooling Total

Mid-efficiency water heater, inside air, uninsulated $(6.62) $21.29 $14.66Mid-efficiency water heater, outside air, uninsulated $(4.82) $15.56 $10.75Mid-efficiency water heater, outside air, insulated $(3.32) $10.99 $7.67

Side-wall vent water heater, inside air, uninsulated $(11.25) $19.14 $7.89Side-wall vent water heater, outside air, uninsulated $(11.08) $16.82 $5.74Side-wall vent water heater, outside air, insulated $(10.67) $15.42 $4.75

High-efficiency water heater, inside air, uninsulated $(6.60) $9.41 $2.82High-efficiency water heater, outside air, uninsulated $(6.43) $9.03 $2.60High-efficiency water heater, outside air insulated $(6.19) $8.58 $2.40

Mid-efficiency furnace, inside air, uninsulated $(5.40) $0.49 $(4.91)Mid-efficiency furnace, outside air, uninsulated $(5.01) $0.19 $(4.82)Mid-efficiency furnace, outside air, insulated $(2.44) $0.18 $(2.26)

High-efficiency furnace, inside air, uninsulated $(3.04) $0.41 $(2.62)High-efficiency furnace, outside air, uninsulated $(2.45) $0.16 $(2.29)High-efficiency furnace, outside air, insulated $(1.21) $0.16 $(1.05)

Mid. Eff. Water Heater and Furnace, inside air, uninsulated $(10.01) $22.19 $12.18Mid. Eff. Water Heater and Furnace, outside air, uninsulated $(8.72) $16.17 $7.45Mid. Eff. Water Heater and Furnace, outside air, insulated $(4.65) $11.08 $6.43


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Seattle

Table 14. Equipment Room Design Heating Temperatures -- Seattle


SpaceHeatingDesign

On-Cycle Off-Cycle

Mid-efficiency water heater,outside air, uninsulated

70.0 28.0 64.9 68.7

Side-wall vent water heater,outside air, uninsulated

70.0 28.0 56.0 78.4

High-efficiency water heater,outside air, uninsulated

70.0 28.0 70.4 74.4

Mid-efficiency furnace,outside air, uninsulated

70.0 28.0 73.6 69.1

High-efficiency furnace,outside air, uninsulated

70.0 28.0 69.5 69.2


70.0 28.0 69.0 67.5

Table 15. Annual Energy Costs -- Seattle

Equipment Room Description Heating Cooling TotalMid-efficiency water heater, inside air, uninsulated $(15.41) $1.52 $(13.89)Mid-efficiency water heater, outside air, uninsulated $(10.35) $1.61 $(8.73)Mid-efficiency water heater, outside air, insulated $(7.12) $1.13 $(5.99)



Mid-efficiency furnace, inside air, uninsulated $(14.42) $(0.00) $(14.42)Mid-efficiency furnace, outside air, uninsulated $(13.32) $0.00 $(13.32)

Mid-efficiency furnace, outside air, insulated $(6.46) $0.00 $(6.46)High-efficiency furnace, inside air, uninsulated $(8.05) $(0.00) $(8.05)High-efficiency furnace, outside air, uninsulated $(6.42) $0.00 $(6.41)High-efficiency furnace, outside air, insulated $(3.12) $0.00 $(3.12)

Mid. Eff. Water Heater and Furnace, inside air, uninsulated $(24.26) $1.55 $(22.72)Mid. Eff. Water Heater and Furnace, outside air, uninsulated $(20.65) $1.64 $(19.01)Mid. Eff. Water Heater and Furnace, outside air, insulated $(10.63) $1.11 $(9.52)


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CONCLUSIONS AND RECOMMENDATIONS

CONCLUSIONS

From the review of code and standards and engineering analysis of typical equipment insulation

and ventilation it appears that the addition of insulation to walls and other surface separatingequipment rooms from conditioned spaces is neither required or cost-effective in most cases.Significantly, the energy analysis shows that total heating costs are increased by the addition ofinsulation in most cases. Although the addition of insulation reduces cooling costs, it appearsthat the total costs of heating and cooling will be reduced for most types of equipment intemperate climates by avoiding the use of insulation in walls and other surfaces of separatingequipment rooms from conditioned spaces.

The energy analysis also shows that providing confined equipment spaces with combustion air

from outside, rather than air from the conditioned space, does not necessarily reduce energyconsumption. Although the use of outside air for combustion reduces infiltration losses to theconditioned space, this outside air also reduces the equipment room temperature and the net flowof useful heat from the equipment room to the conditioned space during the heating season. Theanalysis shows that for a variety of equipment and climate data there is a net increase in energycosts associated with the use of outside air for combustion.Existing gas and energy codes do not directly address all the issues related to the ventilation andinsulation of equipment rooms. In general, insulation requirements related to the interior wallsof equipment room do not directly consider the use of outside air for combustion and ventilation.Rather, the effect of outside air is considered indirectly in both the International Energy

Conservation Code (IECC) and ASHRAE Standard 90.2 by temperature-based criteria. Thesectiteria that would require insulation unless the temperature in the equipment room is maintainedabove 50oF by the heat from the surfaces of the fuel-burning equipment located in the equipmentroom. The energy analysis of this study shows that equipment room temperatures of 50oF aremaintained for most combination of equipment and climate data.

Although the existing gas, energy, and ventilation codes and standards recognize the need toprovide adequate combustion air, particularly where the construction has been tightened toreduce infiltration, the terminology and criteria that define unusually tight construction in theInternational Fuel Gas Code (IFGC) and National Fuel Gas Code (NFGC) are not consistent withthe terminology and criteria of the IECC or ASHRAE 90.2. Although compliance with energy

codes or standards does not require unusually tight construction as defined by the gas codes thereappears to be an opportunity to ensure the energy efficiency and indoor air quality of residentialconstruction by providing a more consistent and easily applied set of criteria.


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RECOMMENDATIONS

The following are provided as suggestions for further research as may be needed to verify andexpand upon the conclusions of this report and as appropriate to disseminate its findings:

Dual approach for dissemination:(1) technical audience for model code acceptance(2) grass roots

Additional installations and monitoring

Peer review of energy model

Publication/presentation of technical results

Dissemination of simplified spreadsheet to practitioners/code officials

Integration of energy, infiltration, ventilation, vent system performance issues

In general, while the various gas, energy, and ventilation codes and standards acknowledge thattight construction, mechanical exhaust systems and fireplaces may require the introduction of

additional makeup air to avoid interference with fuel burning appliances, these codes andstandards do not provide a consistent approach to determine such a requirement or how best tosatisfy it. One problem to development of a simple solution is the complexity and difficulty ofreliably measuring or predicting the interaction of infiltration, ventilation and venting system.

One obvious solution is to isolate fuel burning appliances to confined equipment rooms providedwith outside air for combustion and ventilation. However, such an obvious mechanical solutionmay prelude the development of more comprehensive and reliable solutions that integrateventilation and combustion air requirements with natural ventilation and infiltration.


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APPENDIX A -- INFILTRATION AND VENTILATION CODES

AND STANDARDS

This appendix provides a review and excerpts of the IECC and ASHRAE Standards relatedinfiltration and ventilation. Similarities and differences related to the treatment of infiltration andventilation as presented in various codes and standards are discussed here. This section alsoprovides a review of the energy codes and standards relative to gas code definitions of unusuallytight construction.

International Energy Conservation Code (IECC 2000)

The IECC 2000 provides both proscriptive and performance related provisions. Chapter 4provides a whole-building performance based methodology based on the comparison ofcalculated energy use for a Standard design and a Proposed design where the standard designcomplies with proscriptive standards. The Proposed design need not comply with theproscriptive standards as long as the calculated energy use of the Proposed design is less than thethat of the Standard design.

Chapter 5 provides a component performance approach providing flexibility in the design solong as equivalent component level performance is maintained. For example widow and wallareas and U values can be varied so long as the overall thermal transmittance of the gross wallarea is less than or equal to the code specified minimum overall thermal transmittance. Note thatonly Chapter 5 contains moisture control criteria specifying the use of a vapor retarder.

Chapter 6 provides simplified proscriptive requirements. For example the maximum area ofwindows is specified and tables are provided with the minimum U values for walls, floors,ceilings, and glazing.

IECC 2000 Chapter 4 -- Residential Building Design by Systems Analysis and Design ofBuildings Utilizing Renewable Energy Sources

Air leakage criteria in Chapter 4 are limited to the specification of a Standard design air leakagerate for comparison with a Proposed design. While not explicitly stated it is implied that theStandard design leakage rate is representative of the air leakage that would occur for a house t

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