Insulation of a Vaulted (Cathedral) Ceiling
I live in Canada, and have a low slope (2-12) roof that is shingled. The r-value of the existing insulation would be somewhere between 4 and 7, I think, though there's no way to tell for sure without lifting the roof off, because we have vaulted ceilings inside. The shingles are poor, and I'm looking to replace them, and add insulation at the same time. If I can get the R-value up to at least 28 (and I'd prefer 40 or 60) I can get up to $1800 in grants from the government. If I lift the plywood off the roof, I can add in some insulation, but with only 6" of room, I'd be short of the target. Any thoughts on how to best do this? I've thought of strapping the existing rafters with 2X6s on end, and adding insulation that way. Any better ideas?