If you use foam insulation over wall sheathing, do you still need the building wrap?
Elizabeth Metcalf| Posted inGreen Building Techniqueson
If you house is continuously sheathed and then wrapped with 1″ of foam insulation, with the joints sealed, do you still need the building wrap over the OSB?
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Replies
Shaun,
I did not understand why BSC prefered the housewrap under the foam(between the OSB and the foam) until I read this article.
http://www.buildingscience.com/documents/insights/bsi-038-mind-the-gap-eh/?topic=/new-documents
notice also that they are recommending "crinkly" wrap
MIND THE GAP
Shaun,
Every wall needs a water-resistant barrier (WRB). If you want, you can used taped rigid foam as your WRB. You can also use asphalt felt or plastic housewrap as your WRB. Any of these products can work as a WRB.
Whichever product you choose, be sure to detail the WRB properly. The WRB must be integrated with your door and window flashings, and properly detailed at all penetrations. "Think like a raindrop" to determine whether your WRB is properly lapped and detailed.
Many building scientists believe that WRBs that depend on the chemical properties of the adhesives used in tape and peel-and-stick will prove to be less robust and long-lasting than details that depend on laps and gravity. It's up to you to decide how to detail your WRB.