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What is the best foam board insulation under drywall

Wesley Pracht Published: Jan. 11, 2020, 8:10 p.m.Last updated: Jan. 14, 2020, 9:44 a.m.

I live in Climate Zone 6 in a low humidity, cold, and snowy environment. Heating only no cooling. Currently have T1-11 siding, tar paper, R13 FB insulation, and the interior finish is 1/4 plywood panels.

The siding is in OK shape but I really want the plywood panel interior gone and replaced with drywall. My idea is to tear out the plywood and remove the old FB insulation. I would like to replace with R15 Rockwool and about 1" of foam board insulation attached to the stud and seams taped. Then I would set 1/2" drywall on top of the foam and attached with long screws.

Does this sound like a good plan? Would anyone suggest against using Polyiso insulation as it does not do good in cold environments? Please let me know your thoughts

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