[Greenbuilding] Floating Floor over slab on grade

[elitalking]

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