Hi,

I have a 35 year old house in Minnesota. Last winter we noticed large amounts of frost built up on the bottom side of the roof sheating. He are using a ridge vent and soffit vents where ever possible. The house has a 4/12 pitch which doesn't leave much room above the top plate and roof sheating to allow for insulation and a vent chute. At one time we had the normal tin roof vents about every 6-8 feet near the peak of the roof. They worked fine but we found in a wind driven snow storm snow sifts in through the vent and collects on the attic insulation. Hence the reason we went to the ridge vent. But now it doesn't seem to be getting rid of enough of the humid air causing it to freeze to the underside of the roof sheating. The ceiling does not have a poly vapor barrier. Is the frost caused by a lack of venting or lack of insulation? We have about 7-9 inches of cellulose, and would like to add fiberglass batts over it. Looking for ideas.

Attic Humidity