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Got ice dams? What to do and how to prevent them

March 2019

By Dan Thiede

Ice dams, both awe-inspiring and terrifying, are showing up on many Minnesota homes this winter thanks to heavy snowfall and extreme cold. Find out how to deal with ice dams now and prevent them in the future, which can also save you money on your heating bills.

What to do (and not do) now

One way to prevent ice dams is by removing snow from your roof. While you can try to do it yourself with a snow rake, it may be best to hire a professional snow remover, especially if it takes getting on the roof or using a ladder. Put safety first. If you have an ice dam that is already causing water damage to your interior ceilings and walls, hire a professional ice dam removal service that uses steamers.

A few things you should not do:

  1. Do not install heating cables. They will shorten the life of your roof and add to your energy costs.
  2. Do not remove ice with chippers, chemicals or heat. These can damage shingles, gutters and other building components.
  3. Do not add roof vents, including powered vents. They will not eliminate ice dams and often make the problem worse.
  1. 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, with outside air temperatures near freezing.
  2. When heat leaks into the attic, it melts the underside of the snow on the roof. The water 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 the roof and allowing water to leak to the ceilings and walls below.
  3. Any penetration into the attic space (around wires, plumbing vents, light fixtures, chimneys, knee walls) is a potential for air leaks. Inadequate insulation, especially near the eaves, is also a contributing factor.

Preventing future ice dams

Ice dams are not caused by roofing, ventilation or gutter problems, as often believed. The real problem is a home that is leaking warm air.

Due to inadequate air sealing, heat from the home's interior gets into the attic and melts the underside of the snow on the roof. The melted snow water flows down the roof surface until reaching a cold spot, such as the eaves or soffit, where it forms a frozen dam.

Over time, especially with a snow-covered roof in subfreezing temperatures, more ice can build up. Eventually, water starts seeping into the home.

Because the primary cause of ice dams is warm air leaking from the attic, the best prevention is to seal leaks with caulking or expanding spray foam, with attic insulation installed to a minimum of R-50 as space allows.

Get an energy assessment

An advanced home energy assessment, or audit, is your first step to preventing ice dams and making your home more energy efficient. The assessment will use equipment such as an infrared camera to find attic air leaks and how to seal them.

A home energy audit can be arranged through your local utility, a nonprofit energy group or an HVAC professional.

Once problem areas are detected, get bids from at least two licensed contractors to have the work done.

Ice Dam Videos

Tools for Next Steps

Weatherization Assistance Program

umn extension

Access in-depth ice dam management & prevention info from University of Minnesota Extension.

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