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Curious exceptions to the rigid foam thermal barrier

mackstann | Posted in Building Code Questions on

I’ve noticed that it is common practice for rigid foam to be used on attic hatches and garage doors without being covered by a thermal barrier, which building codes require. Is there some implicit exception for doors/hatches? Or does the small amount of foam used cause it to be simply overlooked?

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  1. Richard Beyer | | #1


  2. GBA Editor
    Martin Holladay | | #2

    If the attic is only accessed for repairs or maintenance, and it isn't used for storage, the foam doesn't need to be protected by a thermal barrier; a less stringent barrier (an ignition barrier) is all that is required. For information on the distinction between an ignition barrier and a thermal barrier, see Thermal Barriers and Ignition Barriers for Spray Foam.

    To make sure that an attic hatch is code-compliant, it would be a good idea to include a layer of 1/2-inch drywall above the uppermost layer of rigid foam. That said, this area of code compliance is very murky -- in part because enforcement of requirements for thermal barriers and ignition barriers is very spotty and inconsistent. When in doubt, talk to your local code official.

  3. Richard Beyer | | #3

    Martin your advice is the minimal code requirement which even architects are questioning. That does not constitute a fire safe home just a minimal code requirement.

    This is what a foam expert posted below referring to the code....

    "Here's the code section from the 2012 IBC dictating the requirement for the thermal barrier:

    2603.4 Thermal barrier.
    Except as provided for in Sections
    2603.4.1 and 2603.10, foam plastic shall be separated from
    the interior of a building by an approved thermal barrier of ½-
    inch (12.7 mm) gypsum wallboard or a material that is tested
    in accordance with and meets the acceptance criteria of both
    the Temperature Transmission Fire Test and the Integrity Fire
    Test of NFPA 275. Combustible concealed spaces shall comply
    with Section 718.

    There are several exceptions to this code citation listed in subsequent sections of IBC-2603, but the above covers most applications in Type-V construction. Types I, II and III construction may require specific tested assemblies or a review and opinion statement from a fire protection engineer."

    Below is case law from the Federal Courts archive where both Plaintiff and Defendant argue over who's liable for a fire where foam was used and covered by a plywood thermal barrier and air space between the two. A spark caused the fire in this case. This illustrates the foam manufacturer did not understand it's own rules. This makes a layman think carefully before acting. It also suggests intumescent paint and a fire barrier are required.

    Is Life Safety really a concern with code or are they to controlled by industry?
    Just my opinion.... The below comments are from the courts opinion...

    "During construction, a spark from a welding torch ignited a fire inside the wall. The gap between the foam and the plywood wall created a "chimney effect," spreading the fire quickly and causing substantial damage."

    "Dole's expert, Joseph Zicherman, testified that warnings should state the need for "a proper thermal barrier over the foam" and there should not be "gaps and large air spaces between the barrier and the foam." However, Zicherman admitted that in some instances plywood would be an appropriate barrier.[2]

    NCFI argues that its warnings adequately conveyed the need for the barrier to be in close contact with the foam. NCFI relied on its warnings of the need to "cover" the foam with a barrier and to "always use a protective coating when applying sprayed urethane foam to the interior or exterior of a building." NCFI claims this language "obviously" indicates a need for direct application. However, there is evidence to support the opposite inference: NCFI employee Ray Mackey testified that the NCFI literature does not address whether there can be a distance between the thermal barrier and the foam. If NCFI's own employees fail to glean this information from the literature, then it is not obvious. In addition, the warnings do not directly address the use of plywood as a barrier.

    A reasonable jury could find that the warnings failed to adequately convey the dangers of using plywood as a thermal barrier and of leaving a space between the foam and the thermal barrier. Accordingly, summary judgment in favor of Dole is reversed."

    188 Ariz. 298 (1996)
    935 P.2d 876
    DOLE FOOD COMPANY, INC., and Dole Fresh Vegetables, Inc., Plaintiffs-Appellants,
    No. 1 CA-CV 95-0300.
    Court of Appeals of Arizona, Division 1, Department C.
    October 24, 1996.
    Review Granted April 29, 1997.
    Review Dismissed as Improvidently Granted June 25, 1997."

  4. Richard Beyer | | #4

    I'm not disagreeing with you, just addressing the murkiness of the code and what industry tells us all.

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