OT: insulating a floor

stovepipe? Posted By stovepipe?, Mar 6, 2006 at 1:45 PM

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  1. stovepipe?

    New Member

    Dec 1, 2005
    I'm insulating a shed and have gotten mixed input on how to insulate the floor. The shed is built on piers, so the "crawlspace" is actually open to the world, not enclosed by foundation. Advice I've gotten is fiberglass batts w/ vapor barrier towards the interior, then something to protect/enclose the batts. I could use foam insulating board for this, I suppose. THis all seems ad hoc to me, though. Does anyone know how one does such a job properly? thanks.
  2. joshuaviktor

    New Member

    Dec 19, 2005
    Northwest New Jersey
    Insulating anything open to the World has its difficulties. Think wind driven dirt, vermin, bugs, moisture, and more specifically, trapping moisture against wood, thereby causing wood to rot.

    The shed has what structure? By that I mean, the piers have beams resting on them? Then joists, then floor planks, or plywood? Or is it lots of piers, with each joist on a pier, then plywood on them? Or what?

    Think about enclosing the shed crawlspace sides, laying a vapor barrier on the dirt to prevent moisture from rising out of the soil, then filling with foam. (NOte, don't do it in this order. Its a lot easier if you finish off with the enclosing the sides bit.)

    Also, think about enclosing the sides, laying that vapor barrier down(visqueen), and stapling fiberglass batts up with the vapor barrier up. Just some thoughts.

  3. begreen

    Staff Member

    Nov 18, 2005
    South Puget Sound, WA
    I would caulk the seams and go with rigid foam insulation. Otherwise, this will likely provide homes and bedding material for most of the vermin in the neighborhood. Installing a rat-wall skirt will also help if it is sunk into the ground 6 inches or more.
  4. saichele

    Minister of Fire

    Nov 18, 2005
    Peronsally, I'd lay some styrene on the top, and then throw some more OSB or similar over that as a floor. Key being no voids. Previous owners started insulating a detached garage by tacking up rigid foam inside on the framing, and the resulting space between the foam and the exterior is perfect habitat for almost everything - mice, squirrels, bats, barn swallows. I moved in and had a damn ecosystem in my garage. And this is in a well-built up area that has been mostly 1/3 acre lots for 40+ yrs.

    If you're committed to insulating underneath, 1st choice would be one of those pro-installed urethane foams. No nutritional value, no voids.

    Next down my list would be the fiberglass, but I'd close the underside of the joists off with some exterior sheathing or at least hardware mesh to keep the critters at bay.

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