Do I need a standard 6 mil poly vapor barrier with dense cellulose exterior wall?
I'm renovating a 1915 bungalow in masachusetts with no existing wall insulation. I've opened the wall cavity and plan to use a dense pack cellulose to achieve R-14. The exterior wall is plank sheathing with paper wrap, followed by shingles, then 1/2 celotex foam board and vinyl siding installed in the 1980's. No rot or leakage is visible from the inside. My question is if I install a poly barrier over the cellulose on the inside under the drywall, will I then cause vapor to be trapped between the outside vinyl /foam board and poly barrier. The foil faced foam board is not completly tight against the underlying shingles and I assume does allow for some air movement underneath it and the vinyl siding.
Personally, I think I would be very cautious in changing your current wall, and i'd probably chose Rockwool over cellulose, then use a smart breathing membrane instead of straight poly
Gregg- Thanks, why do you favor rockwool? Due to its being less prone to moisture issues? I agree with the idea of a breathable membrane on the inside where I will be putting up blueboard and plaster skim coat.