Insulation (venting) questions
Southern Arizona (Zone 2-3); aiming for a modest R30. HVAC ducts are on the attic floor, but nothing else is.
So I bought a 1970s house without attic access, and I can’t say I recommend it. When we finally opened up access, we found a lovely layer of black on much of the OSB, beams, and rafters. Some of the OSB had been replaced, and the R19 FG batts that had once been shoved between the rafters were all over the attic floor–mostly in ineffective piles.
I now have two issues I need to deal with. First, we need to insulate a vaulted ceiling in the master bathroom, outlined in blue in the diagram I’ve attached (hopefully). Some of this room (about 3 rafter bays worth) has soffit vents, but there are no ridge vents and no gable vents. The rafters are 2×8 (7.5″ actual), and I was considering adding 2x2s to make 9″ of space–enough for R30 Rockwool batts (7.25″) and an air gap. Do I also need to vent the ridge? If I were to vent the ridge, wouldn’t I need to compensate for the lack of soffit vents in most of the rafter bays?
Second, I need to do something about the remaining attic problem. Because of the way the roof is set up (hopefully my diagram makes sense!) no vents reach the attic–no ridge vents, no gable vents, and few if any of the soffit vents make it up to the attic because almost the entire perimeter of the house is vaulted ceilings. Is my only option closed-cell foam? I hesitate to spray anything directly on the moldy OSB because we may want to replace a lot of it when it eventually comes time to redo the roof (which is currently only about 2 years old, so we don’t want to tear it out yet if we can help it).
Thank you for any guidance. Researching options has been overwhelming.
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