What is the actual perm rating on open-cell foam – specifically Sealection 500?
There were a series of postings years ago that had links to Demilec’s website as well as others. Those have been pulled. Where could someone find an official perm rating for Sealection 500? Did the companies pull the info for a reason?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
It's right there in the "Downloads" section - http://demilec.com/themes/forms/data/DEMILEC_TDS_SEALECTION_500.pdf
1268 ng/Pa.s.m2 for a 25mm sample...roughly 22 perms (U.S. units) for 1 inch of the stuff (if the conversion factor on Wikipedia is correct - http://en.wikipedia.org/wiki/Perm_%28unit%29).
It's about the same as other open cell foams that I've looked at.
John is right. Conclusion: it's very permeable.