Unvented heat

Unvented heat in cold weather results in ice dams.

Ice dams can form at the edge of a roof because warm air trapped at the top of the attic can melt snow on the roof that, then, freezes as it runs toward the lower, cooler area of the roof.

Ice dams can become a huge problem for homeowners.
Ice dams can become a huge problem for homeowners.
Warm air finds its way into the attic, during winter, because the upper floors of most homes experience some heat loss through the insulation, even well insulated homes. Because warm air rises, the upper portion of an attic is always the warmest. If attic ventilation is not sufficient to vent away this warm air and create a “cold roof” — a condition where the roof temperature is equalized from top to bottom — snow that has collected on the roof can melt.