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Insulation for a new build in zone 5

JAC3232 | Posted in General Questions on

I’m building a brick bungalow in the northern edge of climate zone 5, and I’m trying to decide on insulation for my main floor. My drawing calls for 1” (R6.5) rigid insulation (polyiso) mounted directly on the 2×6 exterior main floor studs, then batts and poly in the bays. Instead of the batts and poly, I would like to do cc spray foam with no interior VB and just drywall with latex paint. Is it okay to spray the inside face of the polyiso? I’m concerned about the heat created when spraying, the vapour permeability for inside drying, and the possible double VB.

I would like to go with a thicker exterior foam (recommended for my zone), but the windows have already been ordered and I’m told this can’t be changed. From my readings on this site, I feel the 1” foam would do more harm than good by allowing condensation to form on the inside during winter.


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