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Building Technologies Program

T OF ENERGY

DEPARTMEN

U

E

NITED STAT S OFA ERICA

M

May 2005 • NREL/SR-550-37583

Installing Windows with Foam Sheathing on a 

Wood-Frame Wall

Building Science Corporation

Westford, Massachusetts
National Renewable Energy Laboratory 

1617 Cole Boulevard, Golden, Colorado 80401-3393 

303-275-3000 • www.nrel.gov 

Operated for the U.S. Department of Energy 

Office of Energy Efficiency and Renewable Energy 

by Midwest Research Institute • Battelle 

Contract No. DE-AC36-99-GO10337

Subcontract Report 

NREL/SR-550-37583 

May 2005 

Installing Windows with Foam 

Sheathing on a Wood-Frame Wall 

January 1, 2004, to December 31, 2004 

Building Science Corporation 

Westford, Massachusetts 

NREL Technical Monitor: Robert Hendron 

Prepared under Subcontract No. KAAX-3-32443-05 
NOTICE

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1 

Installing Windows With Foam Sheathing 

on a Wood-Frame Wall 

Introduction 

Residential housing design continues to move toward the development of high-performance 

sustainable building systems. To be sustainable, a building must not only be efficient and 

durable but also economically viable. For these reasons, new methods of enclosure design have 

been examined that provide high thermal performance and long-term durability and also reduce 

material use (including waste), simplify or integrate systems and details, and potentially reduce 

overall initial costs of construction. 

One new idea relating to enclosure design is to use exterior foam insulating sheathing as the 

primary sheathing and drainage plane for the wall assembly. However, as with any building 

enclosure system, proper details for the management of water, vapor, and energy transfer is 

critical. 

Window systems need to be installed in such a way as to be consistent with principles of 

building science. Window installations also require an understanding of how to maintain the 

continuity of the drainage plane of the wall. 

Background 

As the desire to provide more thermally efficient enclosure assemblies increased, so did the 

problems with moisture accumulation within building enclosure assemblies. Often the problems 

occurred as a result of new materials being introduced into the designs for specific purposes, 

without adequate understanding of all of their properties and the potential impacts on the 

assembly as a whole. Many enclosure failures occurred because of the lack of appreciation that 

products and materials have other properties than the ones that they are initially designed for. 

Though these lessons were hard learned, we can now use this knowledge for our benefit. 

Through examining and understanding materials based on all of their properties (not just what 

they were initially created for), we can potentially eliminate redundancies in enclosure design, 

making the systems simpler and more cost effective. 

In cold climates the use of exterior rigid insulation sheathing boards has been a method of 

increasing thermal performance of the enclosure, as well as a means of reducing the 

condensation potential within exterior wall assemblies. This concept, while not new, has become 

more accepted in recent years and is being used in residential construction. While this method 

has proven to be effective, it was introduced as an addition to standard residential construction 

for a specific purpose. The base wall assembly generally remained unchanged, with other 

materials used for air sealing and water management. 

The opportunity that presented itself was the integration of the exterior rigid insulation board into 

the enclosure assembly to act not only as insulation but also as the primary sheathing and 

drainage plane for the wall assembly. This system, combined with advanced framing concepts, 
2 

can provide cost savings from the reduction of building materials used (fewer studs, the 

elimination of plywood or OSB sheathing, and housewraps), and the reduction of construction 

waste (incorporating standard construction product dimensions in the design of the building to 

minimize cutting). While the use of exterior insulation was initially used in cold climates, the 

benefits of the integrated system from increased thermal performance and reduced costs make it 

potentially viable in other climates zones as well. 

As with any enclosure system, proper detailing for the management of water, vapor, and energy 

transfer is critical. The most important of these for durability of enclosure assemblies is water 

management. 

Window Installation Details 

In most wall assemblies, the connection details around windows have been the source of the 

most problems with water penetration into the building. The following are a set of details that 

describe how to install a window into a wall with insulating sheathing as an integrated drainage 

plane. 
3 

Installing Window with Foam 

Sheathing on a Wood-Frame Wall

Step 1 

Insulating sheathing on 

wood-frame wall 

For the foam sheathing to be an 

effective air barrier and provide 

the drainage plane, the joints 

between the boards must be 

sealed. 

Even with all the joints sealed, 

it is still not recommended to 

have a vertical joint in the 

sheathing occur over a window 

head. The layout of the 

sheathing board over the wall 

area should be done with this in 

mind. 
4 

Step 2 

Install backdam 

A backdam should be installed to 

direct any water that may leak 

through or around the window 

back toward the exterior. 
5 

Step 3 

Apply first piece of adhesivebacked sill flashing; apply 

second piece of adhesivebacked sill flashing

To protect the rough opening from 

moisture and to maintain the continuity 

of the air seal between the wood 

framing and the sheathing, an adhesivebacked sill flashing should be installed. 

Because the exterior face of the foam 

insulation is also the drainage plane, the 

sill flashings must extend out to the 

exterior face of the sheathing. 

The cutting and folding of the adhesivebacked flashing results in “holes” at the 

exterior corners of the rough opening. 

These holes need to be covered to 

prevent moisture infiltration. 
6 

Step 4 

Install corner flashing 

patches at sill 

The “holes” at the exterior corners of 

the cut and folded flashing (from the 

previous step) need to be sealed with 

corner flashing patches. 

The yellow material in this 

illustration shows where the corner 

flashing patches should be applied in 

order to cover the holes at the folds 

in the underlying flashing. 
7 

Step 5 

Install adhesive-backed jamb 

flashing; jamb flashing adhered 

to foam and stapled to frame 

The adhesive-backed jamb flashing is 

installed next so that the joints are shinglelapped to prevent a reverse flashing 

situation. 
8 

Step 6 

Apply sealant at jambs and 

head; alternatively, sealant can 

be placed on the backside of 

the nailing flange (backcaulked); sealants, 

housewraps, and flashings 

must be chemically compatible

Sealant is installed behind the nailing 

flange at the head and jambs to provide a 

seal behind the nailing flanges of the 

window. 

The sill is left open to allow the cavity 

below the window to drain to the exterior. 
9 

Step 7 

Install window plumb, level, 

and square per manufacturer’s 

instructions

The window should be installed as per 

the manufacturer’s instructions. Setting 

blocks and shims should be installed 

between the wood rough opening and 

the window frame (the window should 

no bear on the foam sheathing). The 

window must be anchored to the wood 

rough opening. 
10 

Step 8 

Install jamb flashing 

Flashing should be installed over 

the nailing flanges of the jambs to 

seal the jambs against water 

penetration from the exterior. 

The sill is not sealed allowing for 

drainage of the rough opening, 

back to the exterior. 
11 

Step 9 

Install drip cap (if applicable); 

install head flashing

Installation of a drip cap (if 

applicable) and head flashing is very 

important as the nailing flange at the 

window head can act as a reverse 

flashing directing water into the 

interior. 

One method for extra protection is to 

create a reglet for the drip cap in the 

face of the sheathing above the 

window head. 
12 

Step 10 

Tape head flashing; air 

seal window around entire 

perimeter on the interior 

with sealant or nonexpanding foam

Interior sealant or non-expanding 

foam should be installed around the 

entire perimeter of the window to 

complete the air seal between the 

wall system and the window frame. 

Care must be taken to ensure that 

the foam does block the drainage 

from the sill rough opening to the 

exterior. 
F1147-E(12/2004) 

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currently valid OMB control number. 

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION.

1. REPORT DATE (DD-MM-YYYY)

May 2005 

2. REPORT TYPE

Subcontractor Report 

3. DATES COVERED (From - To)

January 1, 2004, - December 31, 2004 

5a. CONTRACT NUMBER

DE-AC36-99-GO10337 

5b. GRANT NUMBER

4. TITLE AND SUBTITLE

Installing Windows with Foam Sheathing on a Wood-Frame Wall: 

January 1, 2004 to December 31, 2004 

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

NREL/SR-550-37583 

5e. TASK NUMBER

BET5.8004 

6. AUTHOR(S)

Building Science Corporation 

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

Building Science Corporation 

70 Main St. 

Westford, MA 01886 

8. PERFORMING ORGANIZATION 

REPORT NUMBER

KAAX-3-32443-05 

10. SPONSOR/MONITOR'S ACRONYM(S)

NREL 

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Renewable Energy Laboratory 

1617 Cole Blvd. 

Golden, CO 80401-3393 

11. SPONSORING/MONITORING 

AGENCY REPORT NUMBER 

NREL/SR-550-37583 

12. DISTRIBUTION AVAILABILITY STATEMENT

National Technical Information Service 

U.S. Department of Commerce 

5285 Port Royal Road 

Springfield, VA 22161 

13. SUPPLEMENTARY NOTES

NREL Technical Monitor: R. Hendron 

14. ABSTRACT (Maximum 200 Words)

Residential housing design continues to move toward the development of high-performance sustainable building 

systems. To be sustainable, a building must not only be efficient and durable but also economically viable. For 

these reasons, new methods of enclosure design have been examined that provide high thermal performance and 

long-term durability and also reduce material use (including waste), simplify or integrate systems and details, and 

potentially reduce overall initial costs of construction. One new idea relating to enclosure design is to use exterior 

foam insulating sheathing as the primary sheathing and drainage plane for the wall assembly. However, as with any 

building enclosure system, proper details for the management of water, vapor, and energy transfer is critical. Window 

systems need to be installed in such a way as to be consistent with principles of building science. Window 

installations also require an understanding of how to maintain the continuity of the drainage plane of the wall. 

15. SUBJECT TERMS

Building America; Building Science Consortium; BSC; energy-efficient homes; residential housing; sustainable 

houses; enclosure design; exterior foam insulating sheathing; window systems 

16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE PERSON 

a. REPORT 

Unclassified 

b. ABSTRACT 

Unclassified

c. THIS PAGE 

Unclassified

17. LIMITATION 

OF ABSTRACT

UL 

18. NUMBER 

OF PAGES 

19b. TELEPHONE NUMBER (Include area code)

Standard Form 298 (Rev. 8/98) 

Prescribed by ANSI Std. Z39.18
Bringing you a prosperous future where energy is clean, abundant, reliable, and affordable

A Strong Energy Portfolio 

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Energy effi ciency and clean, renewable 

energy will mean a stronger economy, 

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energy independence for America. 

Working with a wide array of state, 

community, industry, and university 

partners, the U.S. Department of 

Energy’s Offi ce of Energy Effi ciency 

and Renewable Energy invests in a 

diverse portfolio of energy technologies.

Research and Development 

of Buildings

Our nation’s buildings consume more 

energy than any other sector of the 

U.S. economy, including transportation 

and industry. Fortunately, the opportunities to reduce building energy use—

and the associated environmental 

impacts—are signifi cant.

DOE’s Building Technologies Program 

works to improve the energy effi ciency 

of our nation’s buildings through innovative new technologies and better 

building practices. The program

focuses on two key areas:

• Emerging Technologies 

Research and development of the 

next generation of energy-effi cient 

components, materials, and 

equipment

• Technology Integration

Integration of new technologies 

with innovative building methods 

to optimize building performance 

and savings

For more information contact:

EERE Information Center

1-877-EERE-INF (1-877-337-3463)

www.eere.energy.gov

An electronic copy of this publication is 

available on the Building America Web 

site at www.buildingamerica.gov

U.S. Department of Energy

Energy Effi ciency

and Renewable Energy

Building America Program

George S. James • New Construction • 202-586-9472 • fax: 202-586-8134 • e-mail: George.James@ee.doe.gov

Terry Logee • Existing Homes • 202-586-1689 • fax: 202-586-4617 • e-mail: terry.logee@ee.doe.gov

Lew Pratsch • Integrated Onsite Power • 202-586-1512 • fax: 202-586-8185 • e-mail: Lew.Pratsch@hq.doe.gov

Building America Program • Offi ce of Building Technologies, EE-2J • U.S. Department of Energy • 1000 Independence Avenue, S.W. • 

Washington, D.C. 20585-0121 • www.buildingamerica.gov

Building Industry Research Alliance (BIRA)

Robert Hammon • ConSol • 7407 Tam O’Shanter Drive #200 • Stockton, CA 95210-3370 • 209-473-5000 • fax: 209-474-0817 • 

e-mail: Rob@consol.ws • www.bira.ws

Building Science Consortium (BSC)

Betsy Pettit • Building Science Consortium (BSC) • 70 Main Street • Westford, MA 01886 • 978-589-5100 • fax: 978-589-5103 • 

e-mail: Betsy@buildingscience.com • www.buildingscience.com

Consortium for Advanced Residential Buildings (CARB)

Steven Winter • Steven Winter Associates, Inc. • 50 Washington Street • Norwalk, CT 06854 • 203-857-0200 • fax: 203-852-0741 • 

e-mail: swinter@swinter.com • www.carb-swa.com

Davis Energy Group

David Springer • Davis Energy Group • 123 C Street • Davis, CA 95616 • 530-753-1100 • fax: 530-753-4125 •

e-mail: springer@davisenergy.com • deg@davisenergy.com • www.davisenergy.com/index.html

IBACOS Consortium

Brad Oberg • IBACOS Consortium • 2214 Liberty Avenue • Pittsburgh, PA 15222 • 412-765-3664 • fax: 412-765-3738 •

e-mail: boberg@ibacos.com • www.ibacos.com

Industrialized Housing Partnership (IHP)

Subrato Chandra • Florida Solar Energy Center • 1679 Clearlake Road • Cocoa, FL 32922 • 321-638-1412 • fax: 321-638-1439 • 

e-mail: subrato@fsec.ucf.edu • www.baihp.org

National Association of Home Builders (NAHB) Research Center

Tom Kenney • National Association of Home Builders (NAHB) Research Center • 400 Prince George’s Boulevard • 

Upper Marlboro, MD 20774 • 301-430-6246 • fax: 301-430-6180 • toll-free: 800-638-8556 • www.nahbrc.org/ 

National Renewable Energy Laboratory

Ren Anderson • 1617 Cole Boulevard, MS-2722 • Golden, CO 80401 • 303-384-7433 • fax: 303-384-7540 • 

e-mail: ren_anderson@nrel.gov • www.nrel.gov

Tim Merrigan • 1617 Cole Boulevard, MS-2722 • Golden, CO 80401 • 303-384-7349 • fax: 303-384-7540 • 

e-mail: tim_merrigan@nrel.gov • www.nrel.gov

Oak Ridge National Laboratory

Pat M. Love • P.O. Box 2008 • One Bethel Valley Road • Oak Ridge, TN 37831 • 865-574-4346 • fax: 865-574-9331 • 

e-mail: lovepm@ornl.gov • www.ornl.gov

Produced for the U.S. Department of Energy (DOE) by the National Renewable Energy Laboratory, a DOE national laboratory.

May 2005 • NREL/SR-550-37583

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