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Additional insulation below laminated/floating floor over rigid-foam-insulated concrete slab?

user-1092095 | Posted in PassivHaus on

I have a 4″ concrete slab insulated with 4″ of rigid foam (on the underside, of course). I was planning to install laminated floating floor on top of everything. As I have to install 2×2″s over the concrete in order to hold the laminated floor, a friend suggested to fill the space between the 2×2″s with insulation or, at least, dirt.

The questions are:

1. Does it really make an energy performance difference (ignoring the “feel” of the floor), to have a ceramic/stone/tile floor over the insulated concrete slab, rather than a floating floor? Just in the areas where I get direct sunlight?

2. In the areas where I will install floating floor for sure (i.e. where I get no direct sunlight), should I install insulation in-between the 2×2″s? Wouldn’t that insulation insulate me from the EPS insulated thermal mass of the concrete slab, which I hope will affect the house with its thermal inertia? Or should I add mud or dirt between the 2×2″s? In that case I wouldn’t be insulating, just adding some thermal mass which will help the heat conduction between the concrete slab and the floating floor. Does that make sense?

Thanks.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Jose,
    There is a simple answer to your question: follow the installation instructions provided by the flooring manufacturer.

    I don't know what brand of floating laminate flooring you are planning to install, but most (probably all) brands of this type of flooring have to be installed on a continuous level subfloor or slab, not furring strips.

    Here is a link to a typical installation manual: Armstrong Installation Manual.

    That manual notes: "Armstrong and Bruce Laminate Flooring can be installed over most subfloors and existing floors on all grade levels. All substrates must: meet applicable building codes; be structurally sound; show minimal deflection; be dry, clean and flat. ...

    "Variations in subfloor flatness should not exceed 3/16" in 10' (4.76 mm in 3.05 m) or 1/8" in 6' (3.17 mm in 1.83 m). Level floors with a suitable cement-based self-leveling underlayment following the manufacturer’s recommended guidelines...

    "Concrete floors must be cured properly and allowed to dry for at least 60 days before installation can begin. Concrete floors must not show any signs of moisture or alkali. Use Quiet Comfort or Quiet Comfort Premium Underlayments for Laminate with no attached backing (or Moisture Barrier Sheeting for laminate with attached backing), butt the edges together and tape the seams with polyethylene tape.

    "All concrete subfloors should be tested, and results documented, for moisture content. Visual checks may not be reliable. Test several areas, especially near exterior walls and walls containing plumbing."

  2. user-1092095 | | #2

    Thanks Martin
    You are totally right, I don't know where I got the idea of installing the 2x2"s.
    Now my question is only one:

    1. Does it really make an energy performance difference (ignoring the "feel" of the floor), to have a ceramic/stone/tile floor over the insulated concrete slab, rather than a floating floor? Just in the areas where I get direct sunlight?

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