Insulating a gambrel roof
I have a newly constructed gambrel roof with dormers. The bottom pitch is 12/12, and the top pitch is 4/12, with a ridge vent installed. I live in zone 5, and the roof is 5/8″ plywood, titanium felt, ice shield on sides, bottom, and dormer roofs. What’s the best way to insulate the bottom pitch, and the attic floor (below the top pitch)? If I don’t vent the bottom and dormers, do I need to vent the end walls above the insulation to use with the ridge vent, or should I seal off the ridge vent, or go with no vents except for the ridge vent? I can use cellulose on the attic floor, and cellulose or spray foam (if needed) on the bottom pitch. I cannot vent from the dormers to the main roof, but I can vent to the dormer roof. But, the rafter joist spaces from the dormers to the peak of the main roof cannot be vented. I can extend the 2×6 joists to get more cellulose. If I use cellulose on both the lower roof and the attic floor, do I need any vapor control? Or, will air sealing the inner living space suffice?
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