Best use of 11 7/8″ space in a cathedral ceiling
I am building a Cathedral ceiling great room using 11 7/8′ engineered I beams in Zone 4A. A vented ceiling is required. No exterior insulation will be possible on the roof. I’d like to know, given the constraints of the 11 7/8′ space, what the optimal configuration of insulation would be? The roof pitch is 10:12 and the exterior material will be metal.
I saw somewhere where a builder used foam sheet to create the air channel. Could that be done, then an inch of closed cell [to create an air barrier] and then the remainder some less expensive blown insulation such as spider insulation? Is there a better channel? A better combination of materials?
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