Flash & batt of conditioned attic
I’m building a new home in Zone 4 (Nashville, tn). It has a conditioned attic with mechanicals. I’m looking for the most cost effective, yet durable, way to insulate it r-38 or better.
My plan is to spray foam then follow up with a batt after furring 2×10 rafters with 2×4’s. I can spray 3 inches of open cell for less than half the cost of 2 inches of closed cell. I’m thinking the OC is the way to go. OC is about $1,800 and CC is about $4,000.
I’ve read through the articles about insulating a cathedral ceiling and is OSB and open cell a bad idea threads. I know the recommendation is to flash with CC, but the cost difference is compelling. Am I asking for trouble by using OC of only 3 inches instead?
My roof assembly is as follows:
peel & stick underlayment
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