The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
What coverings are acceptable for foam insulation used indoors?
I am reinsulating a house that has concrete block walls, a stucco exterior, and 3/4-inch foil-backed gypsum board over furring strips on the building interior.
If I glued foam insulating board directly over the existing plaster wall finish, would paneling be sufficient covering? Will the foil backing on the gypsum board create a cold-side vapor barrier? - Gordon Reed Jr., Kingsford MI.
In the photograph at left, foam insulating board is shown on a garage ceiling below a second floor bedroom - this material should have been covered with fire rated drywall to meet local building code specifications for fire safety.
Answer: Fire Code Requirements for Covering Foam Insulating Board
Since most fire codes call for a minimum of half-hour fire rating over foam insulations, paneling would probably not provide a sufficient fire barrier over the foam insulating board. New 1/2-inch drywall is usually called for [and in some installations, fire-rated drywall or thicker drywall may be required for local codes and for certain applications].
The thin foil used on the back of drywall will create a moderate cold-side vapor retarder, but the exact permenance is not published for foil-backed gypsum board.
The safe tack is to use a highgraade air/vapor barrier on the inside, keeping it much less permeable than the cold side barrier. We suggest foil-faced foam insulating board with the joints sealed with foil tape.
Watch out: depending on whether or not the foil backing on the existing foil-backed gypsum board is perforated or not, the perm rating of that surface could be near zero - that is, very resistant to moisture movement, forming a moisture barrier in the "wrong place".
So it would also be a good idea to take measures to keep interior building moisture levels to a moderate level. See HUMIDITY LEVEL TARGET
Background on foam board insulation and fire protection:
Foam insulation board should not be left exposed in building interiors.
While many modern foam insulating products do not themselves readily support combustion (that is they don't catch fire and burn alone) they may give off thick acrid or toxic black smoke in a fire, making it difficult to safely exit the burning building.
Foam Insulation Alternatives to Solid Foam Board Insulation
Various foam insulation products that are sprayed in buildings, including UFFI, Icynene, Latex, and other insulating foams as well as fire resistant spray foam insulation used for sealing building penetrations, a different product from the foam board insulation discussed here, are described at INSULATION IDENTIFICATION GUIDE and at FOAM INSULATION IDENTIFICATION.
The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article.
Q&A on Covering Indoor Foam Insulation - PDF version, use your browser's back button to return to this page. Original article, Solar Age Magazine, September 1985, adapted and updated for InspectAPedia.com November 2010.
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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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Building Research Council, BRC, nee Small Homes Council, SHC, School of Architecture, University of Illinois at Urbana-Champaign, brc.arch.uiuc.edu. "The Small Homes Council (our original name) was organized in 1944 during the war at the request of the President of the University of Illinois to consider the role of the university in meeting the demand for housing in the United States. Soldiers would be coming home after the war and would be needing good low-cost housing. ... In 1993, the Council became part of the School of Architecture, and since then has been known as the School of Architecture-Building Research Council. ... The Council's researchers answered many critical questions that would affect the quality of the nation's housing stock.
How could homes be designed and built more efficiently?
What kinds of construction and production techniques worked well and which did not?
How did people use different kinds of spaces in their homes?
What roles did community planning, zoning, and interior design play in how neighborhoods worked
"An Example of Colonial Paneling", Norman Morrison Isham, The Metropolitan Museum of Art Bulletin, Vol. 6, No. 5 (May, 1911), pp. 112-116, available by JSTOR.
"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy