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Thermal mass question

Michael Belhumeur | Posted in General Questions on

I’m wondering how much I’ll decrease the effectiveness of a 4″ slab/ thermal mass by laying a thick underlayment (looks like a yoga mat) over the cement floor and installing a floating 5/16″ engineered wood floor over that.

The 4″ cement slab is insulated on all 5 sides with 4″ of extruded polystyrene foam board.
I’ve been living in the home while I’m finishing it and I love how its working during these cold snaps.

So, my question is, if I put this floor & underlayment down, will I be decreasing the thermal mass’s effectiveness by 30%, 40%, 50% or more? Is there a way to find out?
Thank you

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  1. David Meiland | | #1

    Wild guess: with 4" of XPS all around the slab, the flooring and underlayment will barely make a difference.

    Maybe someone with data will come along.

  2. KEVIN ZORSKI | | #2

    I agree with David. The only caveat would be if there used to be significant solar gain onto the slab that now has the wood over it, which would't absorb as much heat from the sun.

  3. Bob Irving | | #3

    other than the solar gain issue, the slab will stay close to air temperature, like a big heat battery, covered or not.

  4. Michael Belhumeur | | #4

    Thanks guys. I feel better moving forward. Have a good one.

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