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Community and Q&A

Is closed-cell spray foam fire resistant or does it spread fire?

Insular | Posted in Energy Efficiency and Durability on

I was surprised to hear that closed cell spray foam if installed in basement has to either have (i) special paint coating to slow down the spread of fire or (ii) sheet rock over it.

Is this a true? Is this an advantage of open cell spray foam, in that it is much more fire resistant?

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  1. user-729621 | | #1
  2. GBA Editor
    Martin Holladay | | #2

    Here's what I wrote on the topic in the November 2007 issue of Energy Design Update:

    "Most building codes, including the International Residential Code (IRC), require spray foam insulation (including foam installed on the interior of basement walls) to be covered with a 15-minute thermal barrier. However, if the spray foam is located in a crawlspace or an attic “where entry is made only for service of utilities,” the code permits the installation of a less stringent covering — an ignition barrier rather than a 15-minute thermal barrier.

    "In sections R314.5.3 and R314.5.4, the IRC defines an ignition barrier as one of six permissible materials: 1½-inch-thick mineral fiber insulation; ¼-inch-thick wood structural panels (e.g., plywood); 3/8-inch particleboard; ¼-inch-thick hardboard; 3/8-inch-thick gypsum board; or corrosion-resistant steel having a base metal thickness of 0.016 inch. Presumably, code officials also permit the installation of thicker versions of any of the six listed materials."

  3. Insular | | #3


    Does this apply to open cell spray foam insulation? I was told by the foam company (that does both kinds) that open cell spray foam does not have these stringent requirements because it is more fire resistant.

  4. GBA Editor
    Martin Holladay | | #4

    Talk to your local code official. In most cases, a spray foam company has to provide documentation from the ICC Evaluation Service if it claims that its product is an acceptable substitute for a code-mandated material.

    Some spray foam companies have apparently submitted test results to local code officials that have convinced the code officials to waive the requirement for a thermal barrier or an ignition barrier.

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