[Greenbuilding] Floating Floor over slab on grade

[john bone]

Hi,
>From this side of the "pond" (Southern England, UK) - we regularly place on
(concrete) ground slab, a DPM (plastic) and timber joists laid on that and
then timber flooring, and put 4"(inch) mineral / glass / sheep's wool / in
between the joists. The DPM laid up the walls to protect the ends of the
joists, from damp / rot, and then trimmed with a sharp knife.

John Bone, BSc Hons, MBEng, 
UK - Building Code official)

-----Original Message-----
From: greenbuilding-bounces at lists.bioenergylists.org
[mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Dan
Johnson
Sent: 14 February 2012 18:21
To: Green Building
Subject: Re: [Greenbuilding] Floating Floor over slab on grade

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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