[Greenbuilding] Insulation Problems

William R Bloom wbloom at unm.edu
Thu Nov 11 12:40:52 CST 2010


Weren't they talking about continuous insulation on the 
inside surface?  I would have to agree about the thermal 
break from the z-bars, particularly with COPPER cladding, 
but if they put another layer of foam on the inside, then 
a layer covering the exterior would be redundant?

On Thu, 11 Nov 2010 11:57:08 -0500
  "J Messerschmidt" <John at fourpointscg.com> wrote:
> Alan,
> That's not a bad idea.  I think it's fair to say that 
>the insulation value is being reduced from R10 to what, 
>an R6 - due to the heat transfer of the metal bars.  I 
>think the key is whether we can safely tape the joints to 
>provide continuous insulation, while allowing drying to 
>the outside.  What's your opinion on that?
> 
> Thanks!
> 
> John
> 
> 
> 
> 
> ----- Original Message ----- 
>  From: Alan Abrams 
>  To: J Messerschmidt 
>  Cc: Thomas Lewis ; 
>greenbuilding at lists.bioenergylists.org 
>  Sent: Thursday, November 11, 2010 11:23 AM
>  Subject: Re: [Greenbuilding] Insulation Problems
> 
> 
>  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
>  www.abramsdesignbuild.com
>  202-726-5894 o
>  202-437-8583 c
>  202-291-0626 f
> 
> 
> 
> 
> 
>  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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