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Re: GBlist: Polyisoc



Glenn

Expert agree that impermeable rigid insulation on the outside of a 
building will not cause moisture problems. The insulating value of the 
foam will keep the cavity temperature above the dew point. You don't 
mention where you're from or what the climate is like. But this rule 
should hold true in all of the US, and I would think southern Canada as 
well. (Canadians, please pipe up!)

You've mentioned the key precautions, controlling moisture sources 
(indoors and possible intrusion of bulk moisture from outside, too) as 
well as _good_ ventilation (spot fans in kitchen and bath, plus 
background operation of at least 8 hours per day). 

There have been several excellent (and more complete) discussions of this 
topic on this list. You should search the mailing list archives at the 
CREST web site (www.crest.org) to see those. 


Bruce S

>my primary concern is that water will condense
>within the wall cavity and either rot the framing or encourage insect
>infestation.


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