[Greenbuilding] Floating Floor over slab on grade

[Dan Johnson]

I'm also intereseted---for a retrofit context, where the slab is already poured and has no insulation. I want to put down vapor barrier, then 4" rigid over the slab, then two layers 1/2" plywood perpendicular to each other, screwed together, then finish flooring.  

Also interesting that a common German low-energy design features an uninsulated slab-on-grade, then a ±10" TJI floor with cellulose insulation sitting directly on the slab, then a wood finish floor.  --Dan

On Feb 14, 2012, at 9:54 AM, elitalking wrote:

> Oh wise list.  Please advise me on a floating hardwood floor over slab on grade.  With a tile floor, I locate the rigid insulation under the concrete slab which includes the thermal mass of slab inside the thermal envelope. However, with these floating floors, I could consider locating the insulation above the slab, below the floating floor.  This would reduce the thermal mass which would allow make the house more responsive to changes in temperature.  However, being that the slab is below this 5/8" layer of wood, I wonder how affective at absorbing heat the slab can be.  On the other hand, if the temperature conditions are constant on both sides and we are planning on achieving tight walls and ceiling with flash coat of closed cell foam, this should provide a bigger thermal flywheel to would soften the affects of exterior fluctuations.  With slab in thermal envelope, the best practice is to maintain temperature.  With slab below insulation, the house could more easily recover from cool temps.  Since the rest of the thermal envelope is holding the air and heat, my instincts are that even if you lowered the thermostat at night, the temp will not go down that much.  With slab it would go down less.  However, it would recover more slowly also.
> 
> I am intersested in your thoughts.
> 
> Eli 
> 
> 
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