The water develops on the roofing nails first because they readily conduct cold.
Frost and ice in attic.
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.
Frost itself doesn t do any damage but once it melts things get wet and then damage occurs.
During winter conditions attic frost is a problem associated with attic bypasses.
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.
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.
Frost in your attic space is a sign that warm humid air is somehow getting into your attic space.
In order to eliminate frost build up in the attic space we have to understand what causes it in the first place.
Ice damming usually occurs with a significant depth of snow on the roof.
Water vapor is migrating upward and eventually filtering into the attic.
When the snowmelt runs down the roof and hits the colder eaves it refreezes.
When the outside temperature rises again the frost thaws water collects and can leak into your house.
Can sun get to the roof you will have either frost or water collecting.
When it reaches the cold surface of the roof sheathing and framing it turns to frost.
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.
Ice dams are the large mass of ice that collects on the lower edge of the roof or in the gutters.
When moisture gets into the attic it condenses on the roof sheathing in the form of frost.
If this cycle repeats over several days the freezing snowmelt builds up and forms a dam of ice behind which water pools up into large puddles or ponds.
When the temperature in your attic is above freezing snow on the roof will likely melt.
Depending on the temperature and the insolation ie.