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A wrench in my crawlspace spray foam insulation plans. :(

Post in 'DIY and General non-hearth advice' started by mfglickman, Sep 25, 2012.

  1. mfglickman

    mfglickman Minister of Fire

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    I've got a couple of estimates in for putting 2" of spray foam on the rim joists and floor joists of my crawl spaces, where currently there is NO insulation.

    Unfortunately, I've learned that I need a fire barrier/retardant on the foam, which can be a special paint (@.95/sq foot applied by the foam company) or 1/2 inch sheetrock, or rockwool applied OVER the foam so it's no longer exposed.

    Has anyone BTDT with this? What did you do? The house has chestnut floorboards so the building inspector laughed and wished me luck should we choose the sheetrock option. Plus the crawls are a little bit humid, I'm not excited about sheetrock down there.

    Also now that I'm looking into doing this people are coming out of the woodwork to tell me that insulating the crawlspace won't do nearly as much as insulatiing the walls. I am not redoing any walls so any insulation would have to be blown/injected through holes.

    Thoughts? Help?

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  2. Jags

    Jags Moderate Moderator Staff Member

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    Not much help with the exception of "NO" to the sheetrock. That will not work out well in the long run. Hmmm...thinking out loud...would tin work (like the roofing on old chicken coops, etc.) Not sure on the specs required.
  3. jeffoc

    jeffoc Member

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    I was in an electrical supply place the other day and they had small cans of fire retardant foam. Maybe it isn't made to be sprayed into cavities, but I would ask the insulation guy about it.
    One corner of my house has a crawlspace and I put unfaced batts this summer. I'm hoping it makes a difference.
  4. Jags

    Jags Moderate Moderator Staff Member

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    Naaa - that spray foam that electricians use is a different cat. Some is designed to simply fire proof a hole that an electrician needed to make, like running a wire through a firewall and some of it is a self expanding foam that when heat hits it, it expands to cover a hole, such as a wiring loom or run that may carry several cables and techs need access to for other reasons. Some of that stuff even comes in bags that you are supposed to lay on a cavity opening so that if a fire occurs it will expand.
  5. semipro

    semipro Minister of Fire

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    Use Roxul instead of foam for your floors? http://www.roxul.com/home
    I think I agree with the folks that insulating walls would be better than floors. Dense pack cellulose can be injected into walls from inside or out.
    Better yet, seal and insulate the attic space first.
  6. jeffoc

    jeffoc Member

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    Jags, I thought maybe it was just for filling holes. Thanks.
  7. Jags

    Jags Moderate Moderator Staff Member

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    Got it. That is exactly what the stuff you were looking at is for.
  8. peakbagger

    peakbagger Minister of Fire

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    When I bought some spray foam for a wall it was offered in fire proof as well as regular versions, there wasnt much of a price difference.
  9. Nickolai

    Nickolai Member

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    My dad and brother operate a cellulose insulation company and for the most part they inject into the walls. From the inside would be best as you don't leave any trace of it behind after a bit of patching and new paint. The wife probably wants new paint anyways right? I've done it to all 3 houses I've owned and it's worth every penny. As for the crawl space, I'd probably avoid it all together unless you're just doing the side walls with foam, which would also have to be fire retardant. I'm certain the guys doing that here just include it in the price, usually around $6/sq ft though!
  10. midwestcoast

    midwestcoast Minister of Fire

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    Have you got a second opinion on the need for a fire barrier? Are they saying you need a barrier between the subfloor and foam or between the foam and crawlspace?
  11. mfglickman

    mfglickman Minister of Fire

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    The CT Building Code (2009 Amendment to the 2005 Code) says that in a crawl or attic space, you need an ingnition barrier between the foam and the crawl (so, spray foam on joists/rim joists, then spray with barrier, which costs $.95 - $1.50/sf). That's a 30% increase in the price of the project, so no small shakes. DH and I were laughing over this, because the foam itself is probably more fire resistant than the 250+ year old wood that is currently unprotected against the oil burner, hot water heater, electrical panel, etc...but if you want to make changes, you have to bring it all up to code, ugh...I get it but it's painful.
  12. Highbeam

    Highbeam Minister of Fire

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    When wood burns it gets hot and displaces oxygen, when foam burns it realeases poison gas. That's the explanation I got anyway.
  13. seige101

    seige101 Minister of Fire

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    Look into finding a contractor that can spray flame retardent foam or look into DIY fireproof paint after they are done.
  14. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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  15. Swedishchef

    Swedishchef Minister of Fire

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    When urethane burns, it produces toxic gases. Trust me, I am a chemist. I won't bore anybody with the specifics.

    That being said, I insulated my entire basement directly on the foundation walls with high density spray foam and then added Roxul on top (after speaking with a building code engineer).

    My suggestion: spray foam wherever you want and then add some Roxul (with some retaining device to hold it in place...). You shouldn't need VB, you'll have a good enough thermal barrier with the foam (depending how much you put)....

    Andrew
  16. mfglickman

    mfglickman Minister of Fire

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    Update - looks like we have to do the ignition barrier. The one contractor who had a foam that passed one of the required tests in the building code, only passed at 4" and we were looking at 2-3 inches. So we are going to do 2 inches + ignition barrier, which will give us R14 (approximately) and the required ignition barrier. Had the barrier not been needed we'd have done 3" for the same price.
  17. ozzy73

    ozzy73 Member

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    I have R 24 value in my rim Joist ( walls are R10 rigid foam with R14 bats on top of that ), two layers of Roxul.

    This stuff is fireproof and has great R Value.

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