Do you need a vapor barrier with cellulose insulation?
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.