The time to prevent ice dams from forming is now—before the snow flies and settles on your roof.
Ice dams are primarily caused by the presence of warm air in the attic, combined with snow on the roof and the right weather conditions. When heat leaks into the attic it melts the underside of the snow on the roof, which then flows down the roof surface until it reaches a cold spot (such as the eaves or soffit) where it forms a frozen dam. The ice buildup can back up under the shingles, damaging them and allowing water to leak to the ceilings and walls below.
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. Inadequate insulation, especially near the eaves, is also a contributing factor.
To avoid ice dams, attic air leaks must be sealed with caulking or expanding spray foam, and attic insulation should be installed to a minimum R-50 as space allows.
A first step to solving ice dams—and to making your home more energy efficient—is to have an advanced energy assessment. The assessment will use equipment such as infrared cameras to identify air leaks and will offer action steps to prevent ice dams. Advanced energy audits can be facilitated by your gas or electric utility and members of the Minnesota Building Performance Association (www.mbpa.us). Once the problem areas are detected, get bids from several licensed contractors and have the work done.
The Division of Energy Resources (DER) offers a fact sheet on ice dams called “Solving Ice Dams.” For more information on ice dams and ways to conserve energy in your home, check out the DER energy guide “Home Envelope” (pages 10-11).
Minnesota Energy Tips is provided twice a month by the Minnesota Department of Commerce, Division of Energy Resources. Contact the division’s Energy Information Center at email@example.com or 800-657-3710 with energy questions.