Indoor Use of Foil Faced Polyisocyanurate Foam Insulation: Hazards?
InspectAPedia® -
Are there any health hazards associated with applying rigid foil-faced insulating foam (polyisocyanurate insulation) on the interior side of walls?
Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
Questions & answers about using polyisocyanurate foam insulation in buildings
This article discusses the question: are there any health hazards associated with applying rigid foil-faced insulating foam (polyisocyanurate insulation) on the interior side of walls?
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.
Sketch at page top and accompanying text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
The question-and-answer article about the indoor use of foil faced insulating foam found just board below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.
Is Foil Faced Polyisocyanurate Foam Insulation Hazardous when Used Indoors?
Are there any health hazards associated with applying rigid foil-faced polyisocyanurate insulation on the inside of the existing walls of a living space?
I am aware that these insulations give off toxic gases as they burn. The question in my mind is whether they are safe on a day-to-day basis within the building envelope with an air change rate of say 0.75 ACH per hour? -- R.H. Mendocino CA
Our photograph (above left) shows Celotex Super Tuff-R polyisocyanurate insulating board used indoors.
Answer:
Rigid polyisocyanurate insulation is foamed from freon gas, a fluorinated hydrocarbon often used as a refrigerant and until the early 1980's, as a propellant in aerosols. [Currently non HFC gases are used for foam insulation production --DF] The earlier-used Freon gas family and modern refrigerants are inert gases and are considered non-toxic, except in very high concentrations of over 1000 ppm [at which point even an inert gas can cause asphyxiation].
The small quantities of gas that will be released from this foam insulating board [until it has "cured" and stopped outgassing] by diffusion or rupture are not considered a health hazard by the several health authorities we contacted. The upper-limit service temperature for this type of foam is 250 degF.
In uncontrolled combustion, all flammable building materials release high levels of toxic fumes. The National Fire Protection Association (NFPA) recommends that all insulation products be contained behind drywall or a suitable fire retarder. A check with your local building officials is almost certainly going to confirm that foam insulation products may not be left exposed in the living area.
In our sketch at page top you will see that the solid foam insulating board in that illustration is placed on the building interior wall surface, but it has been covered with furring strips and then drywall. The furring strips provide a dead air space, increasing the wall's R-value, and the space is in some conditions also used for routing wiring.
The hazard with foam insulation products is of production of toxic fumes or smoke release during a building fire, not outgassing during normal building conditions.
Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.
Questions & Answers regarding this article
Questions & answers about using polyisocyanurate foam insulation in buildings
Question: using polyisocyanurate form insulation in the roof (ceiling) of our out door sauna
(Aug 6, 2011) Diane said:
Hello great article. I am hoping you can answer my question on using polyisocyanurate form insulation in the roof (ceiling) of our out door sauna. We are planing to use them in ceiling then cover them with foil as a bearier then apply the tonge and grove cedar to the ceiling. Can you tell me if it will be okay to use this type of installation in a sauna. My concern is the heat generated by the sauna and off gasing. Please let me know if it is safe to use this product. Thanks for your assistance.
(Aug 7, 2011) Diane said:
Thanks DanJoeFridman for your opinion and information. I will send this web site to our builder to review. And we will be installing a metal roof for the sauna. But I am still unsure about the off gasing of this product. Do you know anything about that aspect of this product?
Reply: Air leaks as a moisture source in roofs versus need for a vapor barrier
DanJoeFriedman (mod) said:
Diane my OPINION is that the installation of a foil vapor barrier forms a perfect vapor barrier - foil has a perm rating close to zero - except if it's cut or penetrated. (It's probably fine for the ceiling covering nails to penetrate the foil where it crosses over ceiling joists).
There are fire code and fire barrier standards that make sense to apply to any occupied building, not just your home, but also outbuildings like a sauna. Check with your building department to ask if the fire barrier formed by the T&G cedar ceiling is adequate to meet the code requirement for covering foam insulation. If it's not, you can add a layer of fire-rated drywall before installing the ceiling boards.
Finally, while I like the energy efficiency of foam insulation installations, I'd take extra care to inspect and maintain the building roof - from outside. A foam-insulated ceiling without ventilation and without inspection access (say a foamed cathedral ceiling) can't be inspected for leaks from inside. Any damage to the roof that causes a leak can result in very extensive damage to the insulated ceiling before you'd notice it indoors.
On a recent foam-insulated ceiling project we opted for a standing seam metal roof for these reasons.
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years.
ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
Excerpts with updates and annotations expanding the original Best Practices Guide text can be found in the online review and book summary at BEST CONSTRUCTION PRACTICES GUIDE and also at DECK & PORCH CONSTRUCTION, at INDOOR AIR QUALITY IMPROVEMENT GUIDE, and in other articles found at InspectAPedia.com such as HOUSEWRAP AIR & VAPOR BARRIERS, SOUND CONTROL in buildings, and other topics.
Tuff-R™ and Super Tuff-R™, Dow Building Solutions, have an R-value of R 6.5 per inch. Note that the R-value of this insulating board is increased to R-9.3 per inch if construction includes a 3/4" air space. These are closed-cell polyisocyanurate insulating foam core board products. The foam core is sandwiched between a choice of exterior faces including aluminum foil, tri-plex aluminum foil, or polyester kraft paper combined with reinforced aluminum foil. One board side is blue, the other is radiant aluminum foil. These products must be covered with a minimum of 1/2" drywall or equivalent thermal barrier in building applications.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Mobile View
