Ice Dams On Well Insulated Roof

An ice dam forms when the roof over the attic gets warm enough to melt the underside of the layer of snow on the roof.

Ice dams on well insulated roof.

The result is a heavy buildup of ice along the edges of the roof. Ice dams and icicles form when the snow melts runs down your roof and refreezes near the edge. What is an ice dam. Ice dams are more frequent if many valleys and dormers complicate the roof or there is a large overhang.

Temperature close to freezing. If left untreated ice dams can rip off shingles crunch gutters and drop the edges of your roof onto the things below them like your car. Moisture entering the home from ice dams can lead to the growth of mold and mildew. A well sealed and insulated attic results in a cool roof and generally will also not have ice dams.

Effects of ice dams. The conditions have to be just right but it can happen. The major issue with ice dams on the roof is that they trap the melting water running down from the top of the roof and thereby cause it the melted water to rise up underneath the roofing shingles and eventually seep through the boards and walls inside our homes. The water that backs up behind the dam can leak into a home and cause damage to walls ceilings insulation and other areas.

The water trickles down between the layer of snow and the shingles until it reaches the eave of the roof which stays cold because it extends beyond the side of the house. An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow water from draining off the roof. More complicated types of roofs hold more snow because they are more prone to have more thermal bridging and air leakage areas. This scenario is often the result of a warm attic.

This only occurs when part of your roof warms to above 32 degrees f warm enough to melt the snow while the roof edge remains below freezing.