Thermal mass question

Michael Belhumeur| Posted inGeneral QuestionsonJanuary 28, 2014 08:22am

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

Answer

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.

Start free trial

Replies

David Meiland|Jan 28, 2014 09:45pm|#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.
KEVIN ZORSKI|Jan 28, 2014 11:15pm|#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.
Bob Irving|Jan 29, 2014 10:33pm|#3

other than the solar gain issue, the slab will stay close to air temperature, like a big heat battery, covered or not.
Michael Belhumeur|Feb 03, 2014 06:53pm|#4

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