Protecting Your Home From Ice Dams

Ice Dam 9

If it seems like you’re seeing more icy formations on houses and buildings this winter, you’re not alone. Alaska Housing's department of Research and Rural Development notes there have been a substantial number of ice dams and icicles this year. 

And while they can be pretty to look at they are also dangerous, damaging to buildings and can create unhealthy indoor environments.

Causes of Ice Buildup on the Roof

Ice dams are formed when warm air from inside the house makes its way into the attic and warms the snow on the roof enough to melt the bottom layer of snow. That water makes its way down the roof to the eaves that are cold.

The water freezes again at this point. The ice dam is the continued build-up of the snow melt from the roof. Icicles form when this water runs off the roof but freezes on the way down to the ground.

Potential for Damage

Water can also become trapped behind the ice dam and with nowhere to go it can seep under the shingles, then run into the ceiling or down interior walls. This can cause damage to the wood or sheetrock and create an issue with mold or mildew if it is not addressed. The excessive buildup of ice can tear down gutters, shingles, downspouts and possibly even overload the designed snow load, causing structural damage to the roof.

Image shows how an ice dam forms on the roof of a house.

Keeping Heat Inside

Heat moves into the attic for two reasons: not enough insulation and/or holes into the attic. The holes can be from things like wiring, pipes, junction boxes, recessed lights or an attic hatch. These areas can be sealed up with caulk, spray foam, backer rod, red tape, aluminum duct tape or mastic.

Insulating materials such as ridged foam, fiberglass, cellulous or rock wool can help keep the heat in the house and the attic cooler. While insulation is vital to maintaining a cold attic space the most important factor to preventing ice dams is air sealing between the house and the attic.

You can learn more about preventing ice dams and icicles on Alaska Housing’s Resource Information Center Library.