Beyond R30 in an almost perfect climate?
The climate here in Oakland Ca. is very temperate. As I’m trying to wrap up a personal building project on my own home I’m stuck on how much attic insulation will help control attic solar gain during those few hot summer days. R30 would be the minimum I’d install as I’ve got 2×4 ceiling joists presently filled with Rockwool. I could either layer another course of r15 or spend a $150 more on r30 fiberglass rolls. (R30 is the only available unfaced FG option available locally.)
So layer with r15 Rockwool or r30 fiberglass?
GBA Detail Library
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