Cost comparisons of R40 wall designs
I am planning a new house to be built in southwestern PA (climate zone 5). I’m following the 10, 20, 40, 60 rule of thumb for insulation R values, but I’m finding it hard to select an R40 design for the above grade walls.
The wall I most liked was a 2×8, staggered stud wall with 3.75″ of cc spray foam in the cavities against the exterior sheathing, then 3.5″ of high density fiberglass bats. This would achieve R36+ for the insulation, reduce much of the thermal bridging and would benefit from the air sealing provided by the spray foam. However, the cost estimate I received for that much spray foam was pushing $32k. There must be a lower cost alternative.
In all the many threads that I’ve read on GBA and elsewhere, I don’t recall seeing a cost comparison for various wall designs. Does that exist somewhere?
For new construction and targeting R40, what is the most cost effective wall design? Opinions…
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