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Getting rid of ice dams

An explanation as to how ice dams form on a roof that leaks heat.

The warmer weather expected over the next several days may be a welcome change for Minnesotans, but winter-weary consumers should also brace themselves for the possible return of bothersome ice dams.

The Minnesota Department of Commerce, Office of Energy Security (OES) reminds consumers that ice dams can lead to expensive repairs and hazards -- and are frequently preventable. Although sometimes thought of as a problem with roofing or attic ventilation, ice dams are actually caused by the presence of warm air in the attic, combined with snow on the roof and the right weather conditions.

Ice dams occur when heat leaks into the attic and melts the underside of the snow on the roof. The melted snow then flows down the roof surface until it reaches a cold spot (such as the eaves or soffit) where it forms a frozen dam, behind which more snowmelt and ice pile up. The ice build-up can back up under the shingles, damaging them and allowing water to leak to the ceilings and walls below.

Source of ice dams

Warm air leaking from the house into the attic is the primary cause of ice dams. Anywhere there is a penetration into the attic space (around wires, plumbing vents, light fixtures, chimneys, knee walls) there is the potential for air leaks. Even homes that are only a few years old may not be properly sealed.

To avoid these types of problems and eliminate most ice dams, attic air leaks must be sealed with caulking or expanding spray foam.


• Sealing attic air leaks saves energy and is key to preventing ice dams.

• An energy audit with an infrared scan can pinpoint trouble spots.

• If snow and ice must be removed, hiring licensed roofing contractors that use steamers is strongly recommended.

What not to do

• Installing heating cables will shorten the life of your roof and cost you money to operate.

• Removing ice with shovels, chippers, chemicals, or heat can damage shingles, gutters, and other building components -- and can be very dangerous.

• Adding roof vents -- including powered vents -- will not eliminate ice dams, and often makes the problems worse.

• Additional insulation -- especially on the top plate of exterior walls -- can reduce heat transfer to the roof deck, but insulation alone is insufficient. Typical attic insulation will not stop air leaks or prevent ice dams.

For more information, visit the website to view and download energy-related documents or to sign up for alerts through email and twitter. Consumers with questions should call the department's Energy Information Center at 651-296-5175 or 1-800-657-3710 (MN only) or at