Cathedral unvented ceiling in California
I live in Santa Barbara, CA (ideal climate) and I am remodeling a home. The roof was built in 1975 by the prior owner. The roof from top down and ceiling are comprised of shingles, paper, 1/2″ plywood sheathing, 3/4″ foam board, then 1 3/8″ tongue and groove. All materials are sandwiched together with no air gaps. The roof is supported by exposed rafters/beams.
I made a tough decision to cover the tongue and groove because I want recessed LED lights, plus the tongue and groove has some defects from the old walls, nails etc. that were removed during remodel. I found low profile LED lights that fit in a 1 1/2″ junction box, so we have rough wired them and attached wood furring strips on the tongue and groove to establish the right level for drywall. Thus, I will have a 1 1/2″ cavity potentially to fill with insulation between the tongue and groove and drywall.
I was going to install 1 1/2″ foil faced foam board tightly in that space, but after reading many articles, I question whether this is a bad idea. I realize the foil will serve little or no purpose without an air gap.i would think the foam can’t hurt, but I don’t expect much since heat will transfer through the furing strips, exposed beams, junction boxes, etc.
What do you advise? Should I skip the foam board entirely and leave the 1 1/2″ unventilated void? It sure would save a lot of work. I could go to 1″ foil faced foam board and leave a 1/2″ air gap between the tongue and groove and foam board, with the foil facing up for a radiant barrier? Or I could skip the foam board and staple some foil across the furing strips for a basic radiant barrier /with 1 1/2″ air gap? Then install the drywall against the foil?
I appreciate your advice.
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