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How to protect rigid foam from fire

dustin_7022224 | Posted in Green Building Techniques on

Looking for a plan to cover otherwise exposed ICF (EPS foam) in a conditioned crawl space.  I’m more interested in a solution that uses a covering that I can paint on with an airless sprayer than some sort of sheathing, but am open to options.

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  1. MattJF | | #1

    DC315 Intumescent Paint is the most commonly used product I have seen. If this is for code compliance, I don’t believe any paint is prescriptive in code and has to be part of a tested assembly. Check the spec sheets for the foam for guidance.

    Drywall is often much less expensive/sf than dc315.

  2. Zdesign | | #2

    FSK Facer wrap which is typically used for fiberglass batts in a basement meets the flame spread and smoke requirements. You will have to check with your local building inspector to see if this an acceptable alternative.

    1. MattJF | | #3

      FSK facer can have flame spread and smoke ratings to demonstrate it is not a fire hazard itself, but that doesn't equate to any ability to prevent another material from catching fire. Unfortunately the current terms and requirements are moderately complex. Random spotty enforcement and a lack of understanding by many inspectors doesn't help things.

      The following is a good explanation

  3. dustin_7022224 | | #4

    I think after some more research, I'm going to pre-rock the interior face of the ICF in the crawl using GP DensArmor Plus - a fiberglass faced gypsum board. I'm going to do this prior to rolling the floor joists, saving the hassle of installing it in an enclosed space. Anyone have experience with it?

    1. Jon_R | | #5

      Foamular XPS insulation claims to be an ignition barrier and will add additional R value - perhaps with a better combination of price/effort/moisture risk.

  4. Ryan_SLC | | #6

    What I have found as I try to find a solution myself is people say Intumescent Paint for the lower code required Ignition Barrier.

    However, I have yet to see this paint be for rigid foam. They are for spray foam. Not to be confusing, I mean to say look at your selected Inumescent Paint and it will likely state it is NOT created for rigid foam. In my mind, if you can't associate your product to a more common product, you're letting the world know something doesn't work 100% with the application on that product--and I don't think it's just foil or pastic facer adhesion as they all claim aggressive latex hold.

    Owens says everywhere their NGX/XPS has to be covered. They don't even pretend it can ever be left exposed. They seem to have the best printed credentials.

  5. rockies63 | | #7

    One thing to think about is whether the sprayed on compound could dissolve the foam - I know certain adhesives can't be used with certain foams for that reason.

    1. Ryan_SLC | | #8

      Right. This area is the most questionable and most purposefully ignored area in building details I can find online.

      I find it odd because R Value isn't going to kill my family, but finding crawl space ignition barrier or thermal barrier protection details? It's no exaggeration to say it's 100% not posted anywhere in detail or beyond a fleeting sentence. Certainly no details.

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