Frost And Ice In Attic

Frost in your attic space is a sign that warm humid air is somehow getting into your attic space.

Frost and ice in attic.

During winter conditions attic frost is a problem associated with attic bypasses. When warm air from inside the house escapes traveling up through the bypasses the moisture condenses on the roof boards and rafters where the frost can form. Depending on the temperature and the insolation ie. Frost and ice forms in attics when warm humid air accumulates and condenses on the underside of your roof sheathing.

The water develops on the roofing nails first because they readily conduct cold. In the parlance of building scientists these cold wooden house parts make up a condensing surface much like a cold glass of ice tea beads with water on a hot summer day. When the moisture gets into the attic it condenses on the roof sheathing in the form of frost. Since our minnesota winters are usually dry the only other source of humid air is your living space.

Water vapor is migrating upward and eventually filtering into the attic. When the temperature in your attic is above freezing snow on the roof will likely melt. Can sun get to the roof you will have either frost or water collecting. When you see water and ice on the nails the actual temperature of the nails is at or below the dew point of the air in the attic that is saturated with water vapor.

When moisture gets into the attic it condenses on the roof sheathing in the form of frost. When the outside temperature rises again the frost thaws water collects and can leak into your house. Ice damming usually occurs with a significant depth of snow on the roof. As more melting snow or rain runs down the roof it meets this mass of ice and backs up sometimes under the shingles and into the attic or the house.

In order to eliminate frost build up in the attic space we have to understand what causes it in the first place. When the snowmelt runs down the roof and hits the colder eaves it refreezes. Ice dams are the large mass of ice that collects on the lower edge of the roof or in the gutters. When it reaches the cold surface of the roof sheathing and framing it turns to frost.