How to insulate stud walls and roof with OSB-wrapped XPS on outside already in place
We have a new construction garage with living space upstairs (room in attic trusses). We are in zone 4, about 10 miles south of zone 5.
The entire interior will be considered "conditioned space". The roof is metal over underlayment over 7/16 OSB over 2" XPS over 7/16 OSB on trusses. The walls are Hardie Plank over Hardi Wrap over 1/2 plywood over 2" XPS over 7/16 OSB over 2x6 - 24" o.c. studs.
Our insulating contractor has proposed the following:
Exterior walls within living space: R-21 kraft fiberglass.
Exterior walls outside living space: 2" closed-cell foam = R-21.
Roof deck: 3" closed-cell foam.
My only concern is the potential for moisture on the OSB between the XPS and the spray foam. From what I can find in my research since I am in zone 4 this should be ok???
BTW per the contractor, this was the recommendation from the NCIF (North Carolina Foam Institute). He was concerned about getting a proper air and vapor barrier throughout the structure.
Comments and advice would be greatly appreciated.
Posted Oct 1, 2012 12:13 PM ET
Edited Oct 1, 2012 1:17 PM ET
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