[Greenbuilding] Slab on Grade Insulation

[Lynelle Hamilton]

I have a slab on grade with a partially back filled north wall (up 5 
feet).  Under slab is R34, walls R 42 walls and R60-70 ceiling.  My slab 
is on traditional footings and foundation wall, 5' below grade (below 
floor level on the north wall.  We sprayed the foundation walls with 2" 
of closed cell (R14), down 15".  My walls are Durisol block.  My floor 
is 4" of rigid foam with 2" of closed cell on top.  Sealed it nicely.

It was 30-33 Celsius here most of the week, but the house never got 
above 20C inside, even with doors opening and closing (I'm still 
trimming out the house).

If I had to do it over, I"d put a bit more insulation in the ceiling 
(had with a 4/12 pitch roof), but I have no real bleed from the floor, 
as far as I can tell (Eastern Ontario climate).

Lynelle

On 08/06/2011 11:51 AM, elitalking wrote:
> I am moving away from using crawlspaces by avoiding ducted heating 
> systems that need them.  I am planning a house using a similar 
> approach the rigid insulation of solar home in Massachusetts.
>
>
>
> http://www.builditsolar.com/Projects/SolarHomes/MAZeroEnergy/MAZeroEnergy.htm 
>
>
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> http://www.builditsolar.com/Projects/SolarHomes/MAZeroEnergy/Montague%20Powerhouse%20As-Built%20Sheet%202.pdf 
>
>
>
>
> In a mixed climate of Appalachian Virginia, I am adding an addition to 
> the uphill side of a house by filling in up to the existing floor 
> level with compacted gravel, rigid insulation and slab.  My client is 
> not as motivated by super high performance as MA residents. I am 
> proposing 2x6 framed walls with flash coat of closed cell to achieve 
> tightness with balance filled with un-faced fiberglass insulation.  
> The slab edge is critical.  If I turn up concrete edge to transfer 
> load from framing, I will need at least 4 inches horizontal, leaving 
> only 2 1/2" for insulation. Another possibility is to put on a double 
> band joist (although there are not joist) to transfer load of walls to 
> footing.  This would give me 3 inches for slab edge insulation. The 
> band could be used as the form for slab.  Our climate is not nearly as 
> cold as MA.  In that house, they also insulated down to footing on 
> interior side of foundation in addition to below 6"xps slab 
> insulation. Is that good value, considering that the 6" XPS 
> significantly reduces the heat flow into the ground?  I prefer the 
> under slab insulation approach over the foundation edge approach 
> because it completes the loop of the thermal envelope.  I am proposing 
> 2 layers 2" xps with a poly layer between to insure tightness. 
> However, we could also stagger the joints and seal.  I like the 
> completeness of the poly without fasteners.  However, how much draft 
> will come through compacted gravel?  This results in an R20 which I 
> can sell to my client. Conventional fiberglass is R19.  Never mind the 
> infiltration flaws of fiberglass.
>
>
>
> This document from buildingscience.com describes both slab edge and 
> underneath approach.  The MA house referenced uses both.
>
>
>
> http://www.buildingscience.com/documents/information-sheets/slab-edge-insulation/files/bscinfo_513_slab_edge_insulation.pdf 
>
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>
> I would enjoy reading suggestions from designers who have used this 
> approach.
>
>
>
> Eli
>
>
>
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-- 
Effective immediately, please use the following e-mail address to reach 
me: lynelle at lahamilton.com