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Community and Q&A

Warmest Insulation Option under floor

neewest | Posted in Interior Design on

I live in the mountains of Colorado, dry and cold.
I live above a loading dock, so semi trucks can drive in and unload the truck under me, so there is tons of cold air that sits directly below my floor. I cannot insulate the ceiling of the loading dock, or make it warmer.
I have a concrete sub-floor.

What is the warmest insulation layer I can put before I install a floating bamboo floor?

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  1. GBA Editor
    Martin Holladay | | #1

    I recommend that you install a layer of rigid foam insulation, at least 2 inches thick, followed by plywood subflooring, screwed through the foam to the concrete with Tapcons. Most builders would probably choose XPS for its density.

  2. neewest | | #2

    Martin, Thanks for the response. If I follow your recommendation, I have to cut all of the doors and the door trims as the new floor will be significantly higher. Could I just use 1" foam with the floor on top of that? Obviously it would be a few inches thinner than your recommendation, so how much colder would it be? Thanks. I am putting my home back together after a flood and am trying to not re-do the entire house with the 7 doors too.

  3. GBA Editor
    Martin Holladay | | #3

    You are in Climate zone 6 or 7. The minimum building code requirement for floor insulation in these climate zones is R-30. Two inches of XPS is only R-10 -- much less than the minimum code requirement. Your suggestion of 1 inch is only R-5.

    Is it better than nothing? Yes. Is it optimal? No. It's your call.

    If you crank up the heat -- especially if you have space heaters directed at the floor -- you can be warm even if the insulation level is very low.

  4. kevin_in_denver | | #4

    Here's a product that makes it super easy by combining the insulation and subfloor in one product:

    I would throw these down without fasteners or glue and just let em float.

    If minimum thickness is the goal, you could put 1/2" polyisocyanurate down, then the floating bamboo directly over that. Overall thickness would be under 1" and the R value is 3.3+. A good quality click-lock flooring system can perform acceptably on foam without a 3/4" solid subfloor, in my opinion.

  5. Ericwest1 | | #5

    I don't think you can buy this vacuum insulated panel flooring in the US, but it would be an interesting solution: NanoFloor

    They have a US office, but the site doesn't list the flooring as a product:

  6. neewest | | #6

    Nanopore can be used in floors, they use it that way in cold places in Europe all the time. The US office was kind of helpful. It is 1.22" thick with the foam under and over their product. It is very fragile and expensive $7-15 a sqft, but love the idea. shows how they do the flooring is the US page
    Thanks Eric West

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