Lightweight concrete floors on upper levels?
I am exploring concrete floors on the main level (over basement) to get some mass into the space. They would be stained and sealed to create the finished floor.
I am researching the use of ICF style forms that would allow a free span from wall to wall and eliminate the wood floor structure all together. An example is Lite-Deck, which costs around $3.25/sqft of floor surface for the form. (plus rebar and concrete).
The other option is a wood structure with (assumed) 2 layers of 3/4″ subfloor, vapor barrier, and then 2-3″ of light weight concrete.
The questions are:
First off, is getting mass on the floors really worth it? It seems to not be overly discussed on this forum, at least search results tend to resemble that. I have about 9% of high (+.50 SHGC) glass on the south that would be in direct contact with the floor. My solar design books lead me to believe I am on the high side of solar tempering and mass may not be overly effective without more glass. However I would also like the mass to absorb the air temp some and help to radiate heat to keep the space at a more consistent temp after the sun goes down.
If so, I am leaning towards the wood floor instead of the ICF form due to the space below the floor to run things such as electrical and 4″ HRV lines. Also install can lighting in the basement. I think cost wise it may be a wash anyway, perhaps the wood floor would be cheaper.
However an advantage to the concrete form would be a thinner floor system, and also a higher level of sound isolation between the basement and main level (in the basement would be the tv/movie area and pool table, etc). The wood structure would need to be 14″ i-joists min. where as the forms would be about 8″ total thickness, allowing me to drop a ceiling below it if I had too.
Anyone have any thoughts/comments on this topic?