Update on polyiso as a WRB?
Mitch_Costa
| Posted in GBA Pro Help on
Martin did an article on Using Rigid Foam As a Water-Resistive Barrier back in Sep 2010. In it he brought up the possibility that polyiso might shrink over time, so might not be reliable as a WRB even though rated for WRB use. Hoping that 5.5 years later there is enough new information for an update on best practices and practicality of utilizing exterior polyiso as a WRB.
Thanks,
Mitch Costa
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Replies
Mitch,
As far as I know, there is no new information on this issue. Assessing different brands of rigid foam for shrinkage is complicated by the fact that manufacturers change their formulas and manufacturing techniques all the time, in an effort to improve their products, save money, or meet environmental regulations. It takes decades to determine how these frequent changes affect shrinkage rates.