Zone 7 but limited to 1.5″ of rigid foam. Worth it?
Been reading a ton of good info on here but still have some questions. I’m planning to strip my Zone 7 2×4 house to the 5/8″ sheathing. I’ve already installed new windows made for 2×6 wall, so built out the frames 1.5″ with 2×4’s under the nailing fin.
I’d like to build the rest of the walls out 1.5″, WRB, then hardie plank siding.
I was considering 2 options:
1- 1″ XPS foam continuous, WRB, 1/2″ furring strips, hardie plank
2- 1 1/2″ XPS foam with furring strips set into furring strip channels, WRB, hardie plank
Problem is, based on the chart I should have 2″ of rigid foam for 11 r value.
Is a little foam better than nothing? or will less than 2″ cause issues down the road?
The house is not airtight with proper vapour barrier on the interior. Walls insulated with fiberglass batts.
Any advice on best route to take is appreciated.
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