What is causing the dripping condensation?
Jim writes from Outing, Minnesota: “I have a 2×12 rafter ceiling, vent chutes, full insulation and 2″ foam. Every spring with a rapid thaw, I have gotten dripping from condensation through the T & G Ceiling. It is a 3 year old 4/12 roof fully covered with ice shield and asphalt/fiber shingles, Heat source primarily wood/ electric baseboard so not high humidity. I shoveled 8″ snow off the roof, no melting, no ice damn, and no shingle damage. I think we may have vapor barrier (poly) between the fiberglass and foam. Foam was taped and caulked. Not sure if it was double vapor barriered or not. May not be poly as foam would have been a barrier? Leakage seems to be at seams of the foam.” Answer: It is common to see some condensation during the winter months, especially in cold climates like Minnesota. Poly is not generally used as a vapor retarder in ceilings. Owens Corning FOAMULAR® extruded foam insulation is not a vapor retarder. It is closed cell but does allow water vapor to pass throug
