I am an architect. I have been looking for options on website and having trouble finding appropriate suggestion. How do I insulate an existing 2x8 @ 16" o.c. cathedral ceiling? (we will be removing sheetrock and replacing with new.)
Answer:
2X8s are 7.25 inches deep and that means that only 6" fibre bats could be put in there unless each rafter is firred down because you need an inch or more for air movement. My system, where possible, is to put in the R-20 bats, horizontally frame down the rafters with 2X6 (on edge) and add another R-20 layer of bats. Yes, the lower layer is compressed but only a bit. Now the vapour barrier can be added and then drywall. Soffit venting and a baffled ridge vent going from gable to gable will complete the job. I wish the contractor had known this when he built a house for me many years ago.
Remember, even if you don’t do your own work around the house have to hire someone, you put yourself at a great advantage when you can intelligently discuss a project with the various trades people.
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