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RE: GSBN:Re: : slab edge insulation

I don't want to differ with any of you. What is a good detail for the slab edge? I personally have the impression that this is probably the most critical detail in a SB building and one that to my mind is still open for improvement. This is what I think it should be:

There should be some form of continuity of exterior insulation from foundation/slab up to SB. No thermal bridges as evident in the infra red Nehemiah Horror movies. To me the preferred method would be to place a form of hard insulation (like the blue/green/pink closed cell foam whatever make) vertically against the exterior of the foundation. I have seen a form of this type of insulation (50mm) with a thin (15mm) cached on cement layer on the exterior for mechanical protection. The panels are purposefully made for exterior perimeter insulation the vertical edges have a tongue and groove profile to avoid gaps. To me this seems ideal. But I still have a few questions.

1) How to attach these panels to the foundation/slab (including stem) before casting with wire anchors in the form boards, or afterwards with some kind of goop? I would prefer the first option. 2) How does the exterior stucco end on top of the insulation? I suggest some of form joggled thin metal stucco stop attached to the top of the stem wall over some of the insulation (20-30mm) then drop 30mm and then move outwards to the exterior surface of the insulation panels form here it drops at an angle for about 5-10mm. The stucco sits on the lip created by the strip but not fully it also juts out a little bit about 15-20mm proud of the exterior surface of the perimeter insulation. Therefore the exterior lip should be stucco thickness minus 15-20mm deep.

I am sure there are other good alternatives to the above solution. The above is still strongly cement based and there are many who prefer to avoid the use of cement. There should also be a solution avoiding the dependence on cement.

At 05:35 AM 3/11/03, you wrote:
I don't think I said don't use edge insulation for radiant slabs
(whereas I might have said that for normal slabs), I said you could get
away from sub slab insulation if you insulated the perimeter walls.  If
you do a radiant slab, even 1/2" of foam between the slab and foundation
wall will work wonders, although 1" is better.
I know that the slab edge in a normal building looks quite bright on a
IR camera (not necessarily equal to total energy loss, just concentrated
energy loss), and that this is a sensible place to insulate, but I don't
think it makes that much of a difference to annual energy cost for
places with 3 or 4000 HDD. When you radiantly heat the slab and/or are
in a cold climate (starting at 6 - 8000 HDD) you should at least do the
perimeter walls.

Why is it again that we cant insulate between the stem wall and the

John Straube
Dept of Civil Engineering and School of Architecture
University of Waterloo
Waterloo, Canada

-----Original Message-----
From: GSBN [mailto:GSBN@...] On Behalf Of Nehemiah
Sent: March 10, 2003 23:07
Subject: Re: GSBN:Re: : slab edge insulation

I beg to differ with John and John.  I did a fair amount of infrared
camera work a number of years ago to see where heat exits a building in
central California.  We would crank the heating system up to a little
bit above what one would normally heat a house to, and then film it
from the outside in the middle of the night.  The three greatest loss
sites for a "normally" insulated house (one that just meets the minimum
California requirements), were (1) the aluminum frames of windows, (2)
the slab edge, and (3) hot water pipes and other pipes (e.g., the
pop-off valve) near the water heater.  Slab edges, when the slab is
exposed to the night sky, account for a VERY significant portion of the
winter heat losses.  Slab edges, when they are tucked under a very wide
eave, account for a lot less.  And slab edges that are insulated, very
much less still.  If a person is going to have a a radiant floor
heating system, then they absolutely should insulate the slab edge.
There are products available that have a hard styrene material
surrounding the insulation.  The hard coating (1) looks good, and (2)
has a key that ties into the slab so that termites cannot pass between
the two building elements.  The insulation is used as the form when
pouring the slab.

Nehemiah Stone

On Tuesday, March 4, 2003, at 05:22 PM, John Swearingen wrote:

> I agree with John Straube about not using slab insulation in SUNNY
> California.  We have areas that have severe winters and deep frosts,
> but in most areas we are designing for cooling loads more than
> heating. Experience, as well as computer simulations, show about a 5F
> lowering of
> ambient  temperatures for four or five summer months when slab
> insulation is
> removed.  The corresponding increase in heating loads is usually
> minimal and
> only significant for a couple of months.
> John
> -----Original Message-----
> From: GSBN [mailto:GSBN@...]On Behalf Of John
> Straube
> Sent: Tuesday, March 04, 2003 1:35 PM
> To: 'GSBN'
> Cc: bainbrid@...
> Subject: RE: GSBN:Re: : slab edge insulation
> I would not use any insul below slabs in sunny california, but would
> use
> it on the stem wall.
> Protection is easy -- you plaster bales? Well you can plaster the foam
> too. The termites are a bigger issue, best solved IMHO with a peel and
> stick over the concrete and down the face of the foam/Mineral fiber
> then plaster over.
> -----Original Message-----
> From: GSBN [mailto:GSBN@...] On Behalf Of Bob
> Bolles
> Sent: March 4, 2003 12:11
> To: GSBN
> Cc: bainbrid@...
> Subject: RE: GSBN:Re: : slab edge insulation
> Hi John
> You wrote"
> <snip>
>> "Finally, if you are using a concrete foundation, adding a couple
>> inches
> of foam or fiber insulation to the exteiror of the foundation is
> likely to be easier and high performance"
> Well, therein lies the problem
> If you place the foam on the exterior, first there is the appearance
> issue, as well as protecting it from damage. Then, I have to ask if
> this would potentially provide a path, behind the foam or through it,
> for termites, ants and other little critters?
> I believe that insulation under the slab is probably appropriate for
> cold climates, but I am working in sunny Southern California. How much

> insulation should we use, if any, below the slab.
> Regards
> Bob
> Bob Bolles
> Sustainable Building Solutions
> Bob@...
> www.StrawBaleHouse.com
>  "They that can give up essential liberty to obtain a little temporary

> safety deserve neither liberty nor safety"  Benjamin Franklin
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Rene Dalmeijer