Exterior closed-cell spray foam to an existing house possibly a slightly different angle
First I apologize as this topic has literally been beat to death….. That said this is a slightly different twist that I cannot find any details on.
Existing house is a 1985 modified split entry. The wall assembly as it exists in the areas I have taken it apart are (from inside out): Paint of various kinds, drywall, foil faced kraft paper (independent of the fiberglass batts), fiberglass batts in a 2×6 wood wall (assuming R-19), fiber board sheathing, probably Tyvek and an old Masonite siding.
I’m looking to tear everything off down to the fiber board, add 1” x 2” strips of XPS over wall studs with a 1/2” plywood face to have a surface to attach siding, define cavity for spray foam, and achieve gap for rain screen. I would then add 2” closed cell spray foam around the entire building to air seal, insulate. The foam will also be the drainage plane.
1) Will the foil faced Kraft paper at the interior surface (assumed 0.5 perm rating or class 2 vapor retarder) be detrimental to the drying potential which is effectively cut in half or inside only rather than in or out?
2) What does the Minimum R-value of the CCSPF need to be (do you use R19 or the effective average R-value of the wall?
3) I’m looking for the windows to be “innie’s” or in the middle of the assembly and I’d really like a flashing detail. I cannot find a good one anywhere with this specific assembly. I will be replacing some or all of the windows, could use one with nail flange but am leaning toward a European window which do not use nail flanges.
4) anybody with any reason not to use Zola windows?
Thanks to anyone that gives any thought to this old topic.
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