What are ice dams and how do they affect roofing systems?
The snow and ice of winter can wreak havoc to your home. Winter creates a special attic ventilation problem in areas where snowfall and cold temperatures are common occurrences. The problem begins with the formation of ice dams – literally barriers formed of ice – that prevent melting water from running off a roof. Ice dams form when the following conditions exist: • Warm air accumulates near the peak of an attic. This occurs because most attics experience some heat loss from attic insulation. • Lower areas of the roof remain cold, especially just above the eave where temperatures may not be much higher than the ambient outdoor air. If the outdoor temperature is well below freezing, conditions are favorable for the formation of an ice dam. • A heavy snow cover accumulates on the roof. Snow not only provides moisture, it also acts as insulation, preventing heat loss from the attic. As a result, temperatures in the attic are typically warmer than when the roof is free of snow. When all t
