Michigan residents experience alternating warm and cold spells this winter should be aware of ice dams.

Ice dams are formed on a home’s roof when heat inside a house enters the attic and melts the snow on the roof. The melted snow drips down the roof and refreezes at the lower level, causing a build up of ice in gutters and along the lower shingles. The ice can ruin these structures, and water can get in the cracks, causing mold and mildew to form.

To prevent ice dams, make sure attic ventilation is adequate through the use of soffit, gable and ridge vents. Examine insulation to ensure it isn’t blocking vents and check its depth. Check all attic ducts to make sure they’re properly sealed and insulated. Make sure exhaust fans lead outside and not into the attic.

Homeowners can also remove snow from the first three feet of their roof when it is safe to do so, though it’s not recommended to climb a roof to shovel the snow off.