[Greenbuilding] Insulation Problems

Alan Abrams alan at abramsdesignbuild.com
Thu Nov 11 10:23:16 CST 2010


building on John S's comments...

...are there some semi rigid strips of something like neoprene that could be
applied over the outside face of the z-bars, that would have sufficient
resistance to compression to support the cladding yet still provide some
thermal breakage before the cladding is attached?  this assumes that the
potential for heat loss through the bridges is so great that even the
addition of R-0.5 btwn bars and cladding would be significant.


AA



*Alan Abrams**
Abrams Design Build LLC*
*A sustainable approach to beautiful space*
alan at abramsdesignbuild.com
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On Thu, Nov 11, 2010 at 11:02 AM, J Messerschmidt <John at fourpointscg.com>wrote:

>  Hi Thomas,
> I love the suggestion of taping the seams and taping the board to z bars.
> With the air leakage to the outside eliminated that would bring us a lot
> closer to the r-10, and it would be a proper drainage plane.  My concerns
> are, what kind of tape and how does water escape if it does get in?  2" of
> xps has permeance of .55.  Will that allow vapor  to escape? What about bulk
> moisture?  Behind the xps is a liquid applied membrane that probably has a
> very low permeance, so it has to dry to the outside.
>
> Lastly, looking at the interior wall assembly, if the open cell foam has a
> perm rating of 8, and 1" of polyiso has a perm of 2.33, this could be a well
> insulated wall and will still dry to the inside.  Right?  Unless I'm missing
> something, we'd end up with about an R30 wall.  I'd be very happy with
> that.  What do you think?
>
>
> Thanks!
>
> John
>
>
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