Q. Does Foam Have to be Covered with a Thermal Barrier?
A. Thermal barrier or ignition barrier requirements for foam can be quite confusing both for builders and code officials. Every code official will interpret the code differently and will impose different requirements, so be sure to always consult with you local code official. However, in general the code does require some sort of thermal barrier in most instances.
Section R314 of the IRC code book requires that spray foam insulation meet specific fire ratings and be covered by a thermal barrier. All foams must achieve a flame-spread rating of 75 or below and a smoke-development rating of not more than 250 according to the ASTM E 84 standard. In other words, all foams must achieve a Class 1 fire rating. All spray foam insulation must be separated from the interior living space by a 15 minute thermal barrier – ½-inch sheetrock being the standard 15 minute thermal barrier. However, an approved material equivalent to a thermal barrier that meets the ASTM E 119 standard is allowed. This would include the use of certain thermal barrier coatings or paints.
According to Section R314.2.3, reduced thermal barrier requirements are allowed in attics and crawl spaces when the entry is made only for the service of utilities. In this instance, the foam shall be covered by 1 ½ inch mineral wool, 1 ¼ inch wood structural panels, ¼ inch hardboard,
3/8 inch sheetrock, or 0.016 inch thick corrosion-resistant steel. In addition, any material that meets the more stringent 15 minute thermal barrier requirements of section R314.1.2 may be used. The reduced thermal barrier requirements would not apply if the attic or crawl space will
be used for storage. The building inspector may, at his/her discretion, decide whether or not the attic or crawl space will be used exclusively for servicing of utilities.
However, three spray foam products, Sealection500, Agribalance, and Icynene, have an ESR-1172 evaluation that allows the product to be left exposed in attics and crawl spaces under specific conditions.