Exterior Insulation & Fiberglass vs Spray Foam
Looking at a new build with 2x6 walls and 1/2" ply sheathing.
I have two options from here:
1 - Tyvek on the exterior & 4" of closed cell spray foam in between the studs for a R26 (but with thermal bridging)
2 - 1" XPS on the exterior, and traditional R20 fiberglass batts for an R25 but no (?) thermal bridging
The building science side of things says I need an R11.5 on my exterior, which would be ~2.5" of rigid board. That's not only is wickedly expensive but also challenging when it comes to installing, siding, windows and doors (according to the contractor). Spray foam would allow the sheathing to dry to the outside - so that's one less thing to worry about. But I introduce the problem of thermal bridging.
I have two options from here:
1 - Tyvek on the exterior & 4" of closed cell spray foam in between the studs for a R26 (but with thermal bridging)
2 - 1" XPS on the exterior, and traditional R20 fiberglass batts for an R25 but no (?) thermal bridging
The building science side of things says I need an R11.5 on my exterior, which would be ~2.5" of rigid board. That's not only is wickedly expensive but also challenging when it comes to installing, siding, windows and doors (according to the contractor). Spray foam would allow the sheathing to dry to the outside - so that's one less thing to worry about. But I introduce the problem of thermal bridging.
Let's hug it out