Spray foam insulation in attic?
I want to insulate a walk-up attic in a 100+ year old home in climate zone 6. I need to add insulation because there is only about a foot of blown in cellulose under the floor boards in the attic. I don’t want to blow in more cellulose because I am thinking about finishing the attic for more living space. I am thinking about having closed-cell spray foam insulation applied against the roof sheathing. The rafters are only 2x4s and I am thinking about firring them out two to three inches to accommodate 5-6 inches of foam. I do not want to firr them out any more than 3 inches because I will lose too much head room. I am also concerned about thermal bridging through the wood rafters. I’ve thought about adding 1.5″ to 2″ thick rigid foam strips to the bottoms of the rafters as a barrier instead of wood. Does anyone have advice for the best way to insulate? I would appreciate it.
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