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new roof, cost effective insulation

steveeee | Posted in Energy Efficiency and Durability on

i’m building a new house in NC, climate zone 4. i have a vaulted ceiling.

i’d like to use a combination of batts between the rafters and rigid foam board. most of the designs I see put rigid board on top of the roof sheeting, then another layer of OSB on top of the foam board to nail the shingles into. so very expensive.

i’d like to put the foam board inside the rafter like this
then the ceiling drywall screwed thru the foam into the rafters.

is that acceptable to inspectors? what would i need to add, like a vapor barrier or something?


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