What is an Ice Dam? What Can You Do About It?

By Reuven Walder

An ice dam is a ridge of ice that forms at the edge of a roof or in a gutter and prevents runoff and melting snow (water) from draining off the roof. The water that backs up behind the dam can leak into your home and cause damage to walls, ceilings, and insulation.

Ice dams form when some areas of a roof are heated above the freezing point while other parts of the roof are below the freezing point. In other words, when your heat escapes into your attic and warms the roof, it can cause ice dams. There are several reasons why a roof could develop such temperature differentials. The most common culprits are:

Poorly or unevenly applied insulation within the attic.
Lack of air sealing between attic and living spaces.
Non-weatherized attic hatches.
Poorly sealed exhaust systems that terminate too close to the roof.
Poorly insulated hot elements in the attic space
Hot, incandescent lights or even recessed lights with direct exposure to the attic.

Eaves, overhangs, and soffit vents will conversely cause these lower parts of your roof to become colder than the sections warmed by the heat in your attic, allowing water to refreeze and form ice sheets that block runoff.

For an immediate fix, you can use a roof rake to remove built up ice and improve water drainage. This should be done by a trained roofing professional as it is extremely dangerous and can damage your roof. In the long term, air sealing and insulating your attic space — as well as proper ventilation to minimize temperature differences between the attic and outdoors — are the most effective means of preventing the formation of ice dams.

If you’ve noticed ice dams on your house, have a Home Energy Auditor inspect your roof and attic area looking for penetrations in your attic isolation and other hazards that can lead to the formation of ice dams as well as moisture buildup and signs of water damage.

[Reuven Walder is Founder/Vice President of Home Services for Ecobeco LLC. He can be reached at 301.802.7038 or reuven AT ecobeco DOT com. He lives on Lombardy Road.] ■