Pole barn post frame insulation
Hello, I am going to be building a pole barn garage/house in Montgomery, Alabama. I have a few questions. The building will be red with a white roof (trying to keep roof cool), vented soffits, full length ridge vent, double pane e glass windows, insulated doors. 36x48x12 building, posts 8′ on center, conventional framing between posts 24″ on center adding 6″ R19 mineral wool, no interior air or vapor barrier. 10-12″ insulation in the ceiling. It will be half house half garage.
1: can I use 5/8″ drywall throughout the house and 3/4″ plywood plus steel ceiling for garage – both will have hvac and be insulated.
2: should I use separate hvac systems for each because of fumes in garage
3: I will build 2×6 wall to separate the two sides, should I sheath the truss above the dividing wall for fire break or hvac reasons.
4: Can my insulation in central Alabama consist of exterior steel-housewrap (air vapor retarder)-mineral wool- interior wall?
5: Should I let them use double bubble radiant air and water (barrier) instead of housewrap (retarder)? Nevermind the R value.
6: The walls will be 7.5 inches thick excluding the steel and interior wall material. True 6×6 posts plus exterior 2x4s.
7: Because of the horizontal 2x4s on the exterior of most pole barns, does it matter if the insulation leaves air gaps around that area as long as the area between the 6×6 posts is full? Otherwise you would need to fill that 1.5″ gap that the 2x4s create plus the 6×6 depth of the posts. That’s a ton of insulation in the south.
I see where some have recommended housewrap before exterior girt installation, is this possible? It doesn’t seem like the posts would be firm enough unless maybe installing the top header plates first. Seems difficult, but I see the sealing potential rather than wrapping outside the girts.
This is not a northern house, I use A/C almost year round. Any suggestions will be greatly appreciated. No I simply can’t afford closed cell spray foam – several quotes in the 11-14k range.