Insulating cathedral ceiling w/polyiso, etc.
I’m preparing to re-insulate my pitched cathedral ceiling(s) with polyiso board (2 layers x 3″ for R40 or thereabouts) and just looking for a sanity check on the foil-side orientation… will have a 2″ vented air gap above – assuming I want the top layer foil side facing the vent space, and assuming the bottom layer orientation doesn’t matter much.
Roof construction is (1989 tract home) 18″ wood web joists @ 24″ oc – will use 1/2″ foam board plus spray foam to insulate the top joist chord and maintain an air seal between the ceiling bays. Filling the web spaces with rockwool.
Going for an “exposed beam” look, wrapping the bottom section of the joists with wood of some kind, while trying to keep the insulation assembly airtight. Layer of GWB over the polyiso board, then decorative wood decking.
Austin, TX – hot/humid climate zone 2b.
Thanks for any/all advice or comments,
(Self-professed DIY hack)
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