Hello all. I rebuilt a roof section on an old house (1924). This roof only covers a closet on the 2nd story. The rafters were 2x4s and the roof had leaked for years around the chimney. I upgraded to 2x6 rafters and added a vented soffit and ridge cap. I've tried to research what would be the best way to insulate this area and have come up with little info.
I was planning on using 3/4" rigid foam as a baffle for the vent--running it the entire length from the eave to the ridge--leaving about 2" of airspace between the roof sheathing and the foam. That leaves me with only about 2 and 3/4" space left over for insulation. All the info I've researched about vapor barriers and vapor permeability has left my head spinning.
Also, instead of drywall I want to cover the closet in T&G cedar. I'm considering just jamming unfaced fiberglass between the foam baffle and cedar. Any thoughts or recommendations??? I'm in zone 4 marine (Tacoma, WA)