Ice Dams: Where Do They Come From?

Ice dams have recieved a lot of media coverage in the past year. After a record breaking winter descended on the East Coast, homeowners and businesses were plagued by ice dams, snow loads, and in some cases roof collapse.

Ice dams are typically caused by melting snow and ice refreezing on a roof. These areas can build up, forcing their way under roofing materials and allowing water into the structure. This melt is caused by heat from the sun, and heat that escapes from the building. The refreezing happens when the water hits a cool area of the roof, like an unheated eave or a shaded area.

Knowing this, we can take a look at a few of the factors that lead to ice dams.

Poor Ventiliation
One way to prevent interior heat from heating your roof is to ventilate beneath the roof. As cool air circulates from vents installed allong the ridge and in the eaves it can prevent snow from melting while exterior temperatures are still low.

Inadequate Insulation
As heat circulates upward from the attic, it melts snow on the roof, which then refreezes on the cooler eave and can cause ice dams. This is amplified if the attic is not effectively insulated to prevent heat loss through the roof.

Lack of Sun Exposure
Ice dams commonly form in areas of the roof that are shaded, or recieve less direct sunlight. Crickets, dormers, and other structural features can create shaded areas that are prime real estate for ice dams. Additionally, in the Northern Hemisphere, north facing roofs often receive less sun. As snow melts from areas in the sunlight and drains to these shaded areas, ice dams are easily formed.

Preventing ice dams comes down to managing the melting and refreezing process. In many instances, adding heat to the eaves or other areas where ice dams are forming can be the best long term solution. Heated roof systems include under roof deicing systems as well as heat tracing cables installed over the roofing material.

Take a look at your roof and keep an eye on any potential trouble spots. For ideas on how to spot ice dams, check out “5 Signs You Have an Ice Dam”.