Radiant Barrier Sheathing - WoodWorks radiant barrier sheathing reduces energy costs 1 ... with...

“The Wood Products Council” is a Registered Provider with The American Institute of Architects Continuing Education Systems

(AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion

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This program is registered with AIA/CES for continuing professional

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material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

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© The Wood Products Council 2012

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LP Building Products is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members are available upon request. This program is registered with AIA/CES for continuing professional registration. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material or construction or any method or manner of handling, using, distributing or dealing in any material or product. Questions related to specific materials, methods and services should be directed to the program instructor. This presentation is protected by US and International copyright laws. Reproduction, distribution, display and use of the presentation without written permission of the speaker is prohibited.

LP Building Products 414 Union Street, Suite 2000

Nashville, TN 37219 www. LPcorp.com

Course Number: LPTS01 Learning Units: 1.00

Radiant Barrier Sheathing


Tony Pugel, Ph.D Senior Process Technologist LP Building Products Nashville TN (615)598-3074 [email protected]

Learning Objectives – Radiant Barrier Sheathing

At the end of this program, participants will:

1. Understand forms of heat transfer 2. Understand how radiant barriers affect heat

transfer through roof systems 3. Understand the benefits of a radiant barrier

sheathing in both a heating and cooling environment

4. Understand radiant barrier sheathing applications and their function, as well as key installation methods

Outline •  Introduction •  Heat transfer •  Radiant heat transfer •  Radiant heat transfer in roofs and attics •  Radiant barrier types •  Radiant Barrier Sheathing •  Other considerations •  Case Studies •  Building Codes and Energy Programs •  Selection and Installation of Radiant Barrier Sheathing •  Summary •  References

Introduction

•  1860 – French scientist Peclet investigated the insulating effect of metals in reducing radiant heat transfer   Visual reflectance or color are not the

determining factors

•  1925 – First patents on reflective surfaces for building insulation   Radiant barrier and reflective insulation

introduced for commercialization

•  1960s – NASA developed thin, metalized films for Apollo space program   Radiant barrier inducted into the Space

Technology Hall of Fame


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Heat Transfer

•  Conduction –  Heat transfer between adjacent

solids, liquids, or gases due to temperature differences

•  Convection –  the transfer of heat from one place

to another by the movement of fluids

•  Radiation –  The transfer of heat through

electromagnetic waves traveling through a vacuums or an air space

Roof/Attic Examples of Heat Transfer

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• Radiation  The roofing materials are radiantly

heated from the sun

• Conduction   The roofing materials conduct heat from the exterior to the interior surfaces

• Convection  The interior surface heats the attic

air causing hot air to rise and exhaust through ridge or gable vents


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Important Concepts of Radiant Heat Transfer

Solar Radiation

Emissivity

Reflectivity

Emissivity + Reflectivity = 1

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•  Radiant barriers are defined to have an emissivity of 0.1 or less

•  To work effectively, low emissivity surfaces must face an air space

Radiant Barrier Properties

•  In summer, heat absorbed by roof components is transferred by infrared radiation to the attic floor

•  Studies show an average of 93% of solar radiated heat enters a building through the attic

Radiant Heat Gain


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Radiant Heat Gain in the Attic

•  Attic heat gain is primarily governed by solar radiation in summer, and more by conduction/convection from the living space in winter.

•  Airflow does not move radiant energy, so increasing

ventilation rate will not replace the efficiency gained by use of a radiant barrier. –  Ventilation is still important for conduction and convection heat

transfer in the attic/roof.

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•  Summer roof sheathing temperatures can reach 160°F with attic temperatures exceeding 120°F

•  Radiant barrier roof

sheathing blocks up to 97% of the radiant heat from being transmitted into the attic

Summer Radiant Heat Gain

Residential Energy Usage (EIA 2013 est.)

Heating/Cooling, 38.5%

Water Heating, 14.1%

Refrigeration, 5.6%

Cooking, 2.8%

Dryer, 3.3% Freezer, 1.2%

Lighting, 8% Washer, 0.5%

Dishwasher, 1.5% TV, 4.8%

Computers, 2.1%

Furnace/Boiler, 2.1%

Other, 15.5%

How radiant barrier sheathing reduces energy costs

1 • Radiant barrier reduces heat movement from the roofing

material to the attic space

2 • The attic space air temperature is reduced and heat

radiated from the roof to attic floor is reduced

3

• Heat transfer from the attic floor to the living space is reduced

• Ducting and air handling equipment in the attic are cooler

Cooling Scenario Apply

Radiant Barrier

Reduced energy costs


Radiant Barrier Types

1.  Foil, bubble insulation, or metalized films usually made with aluminum

2.  Radiant barrier sheathing -

structural sheathing (OSB or plywood) with foil overlay

3.  Interior radiation control coatings – “ radiation barrier paint”

Installations of Radiant

Barrier Types in Attics

Raftet

Rafter

Rafter

Rafter

Roof Sheathing


Roof Sheathing

InsulationJOISt

JOISt

Living Space

Attic Space

Attic Space

Attic Space

Radiant Barrier foil/film may be

placed in a number of

locations in the attic

Radiant Barrier Sheathing is

placed with the foil facing the

attic space

Interior Radiation Control Coatings are sprayed onto the underside of

the roof sheathing

Rafter

Rafter

Horizontal and Rafter Mounted Radiant Barriers

•  If interior attic gable walls are covered with the radiant barrier, roof-deck and rafter-mounted radiant barriers provide equivalent ceiling heat gain reductions to horizontal installations

•  Horizontal application of a radiant barrieron the attic floor is more likely to accumulate dust which increases the emissivity of the surface

•  The main feature of the rafter mounted radiant barrier

is the reduction of radiant heat flow into the attic space –  Especially important for air conditioning and ductwork



OSB Sheathing

Adhesive

Aluminum Foil

Standard OSB roof sheathing (PS-2 Exposure 1)

~0.0025” thickness foil with adhesive and kraft paper backing

Maintains bond of foil to OSB during the lifetime of the sheathing


•  Concern that heat would melt or degrade composite shingles

•  Studies have demonstrated that hot summer day peak shingle temperatures with a radiant barrier were only 2-5° F higher.

•  Most roofing manufacturers do not limit applications with radiant barrier sheathing. You should check with your roofing material manufacturer about your specific application.

Radiant Barriers and Shingles

Other Considerations with Radiant Barrier Sheathing

•  Cell Phone Reception –  As with other metal building components, an already weak cell

phone signal may be influenced by the presence of radiant barriers in attics and walls

–  Cell phone reception issues should be addressed through the service provider

•  Moisture condensation on foil surface –  Normal daily cycle of cooling and heating is not typically a

problem –  Air and moisture movement from the living space to the attic

space may result in condensation


•  With R-19 insulation in the attic floor, radiant barriers can reduce summer heat gain by 16-42%

•  The installation of a radiant barrier resulted in peak energy use reduction three times greater than if attic insulation was increased

•  The value proposition for radiant barrier sheathing is that it is an economical alternative to increased mass insulation because it addresses the predominant source (radiation) of heat in attics

Energy Savings

Energy Savings

Energy Savings are dependent upon: •  Climate •  Roof slope •  Ventilation rate •  Location of the air conditioning and heating equipment and

ductwork •  Orientation of the home •  Insulation levels •  Window area and efficiency, number of occupants, etc.

•  Compared attic and ceiling temperatures, duct temperatures and flows, and A/C electricity consumption before and after installing a radiant barrier on the roof sheathing

•  New unoccupied home in Austin, Texas

Lawrence-Berkeley Air Conditioning Attic Duct Study

The Home •  Living Area: 1520 ft2

•  Slab on Grade with flat ceilings •  Roof pitch: 6 in 12 •  Brown composite asphalt shingles

•  R-38 ceiling insulation •  R-6 duct insulation •  Both air handler/duct system located in the attic •  Air infiltration measured

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Air Conditioner Attic Duct Study

•  A/C energy consumption was 16% less •  80% of decrease due to reduced radiant heat gain by attic duct system

•  The study: –  20 to 30 temperature measurements were made in 7

similar matched pairs of houses in the Houston area –  one house in each pair had radiant barrier roof

sheathing and other house had traditional sheathing

•  Radiant barrier homes had: –  reduced attic surface temperature in the range of 17°

to 29.9°F –  ambient attic air temperature reductions were on the

order of 12°F to 21°F –  A/C coil temperature reductions in the range of 22°F

to 27°F.

Huntingdon Engineering and Environmental, Inc -Centex Homes Study – Houston

Kenetech Resource Recovery, Inc – Austin, Texas

•  Evaluated the annual energy use/cost for a home •  Savings provided payback for cost of product in about 2

years and an estimated 40+% rate of ROI •  Savings due to a significant reduction in heat transfer

through the ductwork

The study: •  In 1999-2000 two unoccupied identical homes were monitored. •  Radiant barrier roof sheathing versus conventional roof sheathing

•  R-30 blown in fiberglass insulation above the ceiling; R-11 insulation in the walls; R-22 insulation below the floors

•  Heated and cooled via identical electric heat pumps with all ductwork located in the crawl space and the air handler located within the conditioned space

•  Monitored for electric energy consumption temperatures and monitored at various locations within the homes, the attic spaces and the outdoor temperature

LP Building Products Roaring River Energy Usage Study

LP Building Products Roaring River Energy Usage Study •  14% summer monthly energy savings with radiant barrier sheathing •  4% winter monthly energy savings with radiant barrier sheathing

FSEC has published several reports on radiant barrier technology, including the effects of:

Florida Solar Energy Center (FSEC) Studies

•  Ceiling insulation level, •  horizontal versus roof/rafter

installation

•  dust accumulation •  surface degradation

Florida Solar Energy Center Study Results

•  All other things being equal, the percentage reduction in ceiling heat transfer for attic radiant barrier systems as compared to standard attics should remain constant regardless of ceiling insulation level.

•  Heat gain of the attic is reduced at the plane of the roof

mounted radiant barrier, which is always above the insulation, so the net heat flow is reduced before it passes through the insulation.

•  Most insulating materials are evaluated individually using a conductive heating procedure –  Uses hot air or a hot surface to generate heat flow through a

material

•  Radiant barrier sheathing cannot be evaluated using this test method

•  Because radiant barriers require an air space they must be evaluated as an assembly –  Aluminum is the only material exempted by FTC requirements on

insulation when used for radiant barrier

Building Codes and Design


Building Codes and Design

•  Some jurisdictions prescribe or allow the use of radiant barriers in roofs to meet insulation specifications –  Austin, Texas and other municipalities –  California (2013) –  Florida (2010) –  Honolulu

•  Design using overall assembly R-value –  Includes air spaces with reflective materials –  Use energy rating programs: see resources such as RESNET®

approved software

•  Consult with radiant barrier sheathing manufacturer, consulting engineer, local code authorities, etc. to understand requirements

Radiant barriers are included in DOE Energy Star Program

Oak Ridge National Laboratory Energy Savings Calculator

•  Oak Ridge National Laboratories offers a simple energy savings calculator on their website (Radiant Barrier Fact Sheet)

  Based on modeling program – AtticSim and EnergyPlus

•  Calculator only for attic applications in the cooling season

1a. Select Climate Zone

or

Radiant Barrier Calculator

Radiant Barrier Calculator


•  Most OSB sheathing manufacturers make radiant barrier sheathing panels

•  Wood structural panels may absorb moisture during construction

•  Perforations prevent the aluminum overlay from acting as vapor barrier

•  Proper perforations reduce trapped moisture in the OSB substrate and reduce re-drying time

Selecting a Radiant Barrier Sheathing

Installation of Roof Radiant Barrier Sheathing

•  Attic sheathing installation –  Protect from moisture prior to

and during installation. Keep the foil side clean.

–  Place panels with foil side facing down (toward attic space) on rafters, trusses, and gable attic walls

–  OSB surface still placed up for safety

–  Radiant barrier sheathing has same nailing patterns as conventional sheathing

Radiant Barrier Sheathing Installation

Radiant Barrier Sheathing foil facing down

¾” minimum air gap

Roofing Material

Insulation

Radiant Barrier Sheathing Installation

•  Radiant barrier should be placed face down, toward the interior of the attic

•  In a vaulted ceiling configuration, a 3/4" air space between the aluminum layer and another surface is required

•  Radiant barrier sheathing panels used on the gable ends of an attic are installed in the same manner

–  Aluminum face toward the attic space

Gable End Installation

Installation of Wall Radiant Barrier Sheathing

•  Foil surface should face out, toward the exterior of the home

•  Use furring strips to create ¾” separation between the foil and the siding

•  In hot climate zones, you may use only on south and west walls

•  Protect radiant barrier sheathing

panels from moisture and rain before and during construction –see installation directions

Outline •  Introduction •  Heat transfer •  Radiant heat transfer •  Radiant heat transfer in roofs and attics •  Radiant barrier types •  Radiant Barrier Sheathing •  Other considerations •  Case Studies •  Building Codes and Energy Programs •  Selection and Installation of Radiant Barrier Sheathing •  Summary and References

•  Ceiling heat flow reductions due to radiant barrier sheathing may: –  Reduce attic temperature by up to 30°F in

summer –  Produce summer cooling energy savings of up

to 17% per month –  Reduce monthly winter heating cost by up to

5%

•  Savings are dependent upon:

–  Building design –  Climate –  Location and insulation of ducts –  Localized conditions

•  Radiant barrier sheathing is a cost-efficient and installation-friendly product for achieving energy savings

Summary

General References

•  A Summary of Fifty Years of Radiant Barrier Research (RIMA-I website, 2012)

•  A Comprehensive Review of Radiant Barrier Research Including Laboratory and Field Experiments ( ASHRAE Transactions, 2012)

•  Radiant Barrier Fact Sheet (Oak Ridge National Laboratory, 2010) •  RIMA-I Handbook: Reflective Insulation, Radiant Barriers, and

Radiation Control Coatings (RIMA-I Website, 2002) •  Radiant Barriers (DOE, 2012) •  Analysis in Support of the Radiant Barrier Fact Sheet 2010 Update

(ASHRAE, 2010) •  ASTM Standard C1743: Standard Practice for Installation and Use of

Radiant Barrier Systems in Residential Building Construction (ASTM 2012)

Questions?

This concludes The American Institute of Architects Continuing Education Systems Course

Tony Pugel LP Building Products

[email protected]

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