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Community and Q&A

Interior Foundation Insulation

camdijion | Posted in Energy Efficiency and Durability on

Hello all,

I live in climate zone 6, and am looking to insulate the interior walls of my basement with EPS. This won’t be a finished space but there will be storage. I’m getting a little lost in the IBC/IRC code. I would rather not cover the foam with mineral fiber, wallboard, drywall etc, and have found a couple thermal barrier coatings online that supposedly can cover EPS. Do they make EPS that adheres to the minimum flame spread/smoke numbers? I am familiar with some of the other options for insulation such as Thermax, but it is a significant amount of money and I wasn’t looking for an insulation with facing. Lastly, I doubt our towns code official will say anything regardless of what I do, but for safety, should I worry about the flammability/melting, and would it be prudent to cover with something? Mechanicals in basement are ground source heat pump, HPHWH, and ERV. 

Any information will be much appreciated

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Replies

  1. Expert Member
    MALCOLM TAYLOR | | #1

    camdijion,

    Yes you should definitely use a code compliant assembly for safety reasons. Foam fires are extremely dangerous.

    There also seems to be a misapprehension about the necessity following building codes that comes up a lot here on GBA. Most of North America has enacted building codes, which are in effect whether they are locally enforced or not. The consequences of not following them have primarily to do with liability. Knowingly doing unpermitted work, or work that does not meet codes, can void home insurance policies, and open you up to personal liability. It's a bad idea.

  2. Ryan_SLC | | #2

    YES! Everything here is about "code is minimum, we do better than minimum!"

    But even the highest regarded here say local inspectors will dictate safety requirements for FIRE?

    Zero sense.

    I have yet to find a picture of a crawl space detail that is even up to code.

    1. Expert Member
      MALCOLM TAYLOR | | #3

      Ryan_SLC,

      I think you are confusing two things. Code minimum is by definition the lowest standard you must reach for approval, but it doesn't follow that a code minimum house is necessarily poorly built, or that going above that for most things makes any sense.

      When people talk about going beyond code minimum they are referring to very specific things. Here on GBA they are mainly to do with air-sealing, building envelope design, and levels of insulation. They still adhere to all sorts of general code provisions and safety requirements without deviation - railing design, structural spans, room sizes, stair dimensions, egress, fastener schedules, and fire protection being a few.

  3. Expert Member
    Michael Maines | | #4

    Foil-faced Thermax is the only foam product I know of that has passed fire safety testing. It is expensive but because it's a one-step process it can save a lot on labor.

    Intumescent coatings are available (and required, in most situations) for exposed spray foam; I don't see why they wouldn't also work on rigid foam. It would need to meet the flame spread and surface burning requirements in this section of the IRC: https://codes.iccsafe.org/content/IRC2021P1/chapter-3-building-planning#IRC2021P1_Pt03_Ch03_SecR316.

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