Ice Damming: build your house for a Canadian Winter
A HOMEOWNER'S GUIDE
What is an Ice Dam?
An ice dam is a layer of ice that forms at the edge of a roof, above the soffit area, which prevents melting snow (water) from draining off the roof. Ice damming is a serious issue that can cause significant damage to your property. It can lead to water leakage from the roof into a home, damaging walls, ceilings, insulation, and the entire building envelope. Roof ice dams can also cause moisture issues, leading to the growth of mold and mildew.
Many people believe that the pitch of the roof affects the likelihood of ice damming, thinking that the steeper roofs are less susceptible. However, ice damming is more related to attic insulation than the roof pitch.
How Ice Dams Form
Here's how it happens:
In the winter, when hot air from the house escapes through the ceiling into the attic, it warms up the attic space. This warm attic space melts the snow on the roof. As the snow melts, water runs down under the snow until it reaches the soffit area, which is hanging over the house, and freezes at the edge. The soffit area is not insulated and is not affected by the house's warm air.
As the melting continues, layers of ice start to build up. This ice buildup traps water between the ice and shingles, which eventually finds its way through the shingles and leaks into the house.
Preventing Ice Damming
One of the main reasons for forming ice dams is improperly insulated attic space. Proper framing and insulation of attic space are crucial in preventing ice dams. You can learn more about attic framing and insulation tips in our other blog posts.
Here are some reasons that can cause the attic space to warm up:
Even with a thick layer of insulation, heat loss might still occur due to improperly framed and insulated attic access and light fixtures. It's challenging to properly insulate and air seal around them. Heat loss can also come from electrical or other wiring holes, duct pipes, and air ventilation pipes.
The importance of air sealing and insulation often goes unnoticed. Even if the cost of utilities such as electricity and gas doesn't bother you, the consequences of not having proper attic insulation or a building envelope will cost you more than just monthly heating or cooling bills.
Long-Term Solutions
In the long run, the risk of ice damming can be mitigated by controlling heat loss from the home. Having a thick layer of insulation, sealing all potential air and heat escape points properly, and ensuring natural air ventilation between the soffit and ridge will help significantly.