Air-Sealing a Cathedral Ceiling
I’m in zone 6 and would like some advice on details on a new construction cathedral ceiling. It’s a simple roof with no hips or valleys. I’ve read numerous articles about T & G wood products being a terrible choice for cathedral ceiling due to warm air rising through to the underside of the cold roof sheathing and condensing.
I have 6/12 24″ deep parallel chord trusses and have installed a baffle system that creates a 2″ air space from eave to ridge using recycled 1 1/2″ polyiso. I am very pleased with the rigidity of the foam and I’m confident I can make the underside of the polyiso baffle system air tight. I plan on filling the remainder of the truss space, 20″ with insulation. I’m also debating on whether or not to add another layer of recycled polyiso on the underside of the truss.
So my question is: With the air tight site built baffle system, do I have to be concerned as to how I treat the ceiling below? I realize best practice, if I wanted to use wood for the ceiling, would be air tight drywall attached to the bottom chord of the truss, 1x or 2x furring strips and then wood on the underside attached to the furring. I’m not hell bent on a finished wood ceiling, but I feel it would be a nice touch. I’m also wondering whether I could attach the finished wood ceiling directly to the bottom chord of the truss. I know I have ample insulation, but does inadequate air sealing on the underside reduce the effectiveness of the insulation above?
Thank you in advance.
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