Proper vapor barrier for back porch remodel / insulation
We are in the process of remodeling a back porch and trying to turn it from a 3-season porch into part of the living area. I currently reside in the US in a Zone 5 climate and our city follows the 2009 International Building Code.
Walls. 2×4 that we have furred out with 2×2 and are planning on doing a flash and batt technique with 2” of closed cell foam and then fiberglass insulation. We are debating on if we should use kraft paper for the fiberglass. Then ½” drywall.
Ceiling. 2×4 that we have furred down with 2×2 and plan to fill entire 5” with closed cell foam. Then we are planning on using 1” of XPS on the interior side in order to meet R38 which is needed for energy rebate. Then ½” drywall.
Are additional vapor barriers needed for either the wall or ceiling? Are there any concerns about condensation between the 5” closed=cell insulation and 1” XPS insulation for the ceiling? Would it be better if we furred down the ceiling further and did the entire thing with closed cell? We liked the idea that the XPS would serve as a thermal break for the studs and additionally it was significantly cheaper than the spray closed cell insulation.
Any suggestions are greatly appreciated.
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