Is this an adequate wall design for Zone 6 in New Hampshire?
1. 5/8” sheetrock
2. “smart” vapor retarder
3. Roxul R-23 batts
4. Avantix sheathing (taped)
5. 2” of type X XPS foam (taped)
6. (Hardie wrap?),
7. 3/4″ strapping (?+Coravent SV5 product on top and bottom of walls and windows)
8.Hardie clapboard siding
Three issues we’re still not entirely sure about are (1) we barely meet the green builder recommendation for R11.25 on the outside, and just fall short of the 36% of the total insulation on the outside (we estimate it is about 34% if we give an R=1 for the air trapped behind the Hardie Board, and R=5.5 for the XPS in the cold. (2) the type of “smart” vapor retarder on the inside; (3) where in the wall the Hardie wrap should go (we understand that it goes on the outside of the foamboard if the windows are “outie” and that’s where we’ve put it for the moment); (4) type of XPS – it comes in sheets but also in a finger jointed product from DOW, we’re not sure how these compare in terms of cost, ease of installation and quality of the finished product.
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