Zip Wall Sheathing and Vapor Barrier
We have a house under construction that is weather tight. It uses the Zip wall and roof systems and will have 5″ of closed cell insulation in 2×6 walls, 6″ in 2×12 cathedral rafters. I have read well informed people on the web saying that if the outside is not permeable (Zip isn’t) then the inside should not use a vapor barrier. The logic is that water will get in and will need to go somewhere otherwise the interior of the wall will not dry.
Is this what the pros do in the field?
Thanks
Al Charbonneau
Replies
Al,
Yes, that's what the pros do -- if they understand building science instead of following myths and rumors they pick up at the lumber yard.
Zip & vapor barrier
So Martin, are you saying if Zip sheathing is used, then don't include paper-backed batt insulation? Not sure I am comfortable spec'ing insulation without vapor barrier.
Michael
FWIW, both your zip panels and your closed cell are pretty much vapor impermeable.
If bulk water somehow gets into that assembly it will be very slow to dry. How are you installing your windows and doors? Any roof-wall junctions?