Image of icicles along gutter on home

Ice Dams

Dear Sustainability Sam,

Walking around the neighborhood both last year and more recently, I have noticed a lot of ice dams on buildings. I’ve heard that ice dams are caused by poor insulation. Is this true? What are the potential environmental impacts of ice dams and poor insulation?



Dear Richard,

Yes, it is true! Ice dams are caused by warm, moist air from inside your home rising up into your attic space. This warms the roof of your house and causes the under layer of snow on your roof  to melt and run down the roof shingles. When it reaches the cold overhang it freezes causing a dam to form on the eaves. As the winter progresses this process occurs more and more and the dams get bigger and bigger.

There are a few reasons you want to avoid ice dams. First, they are a sign of heat escaping your home which is inefficient. In Minneapolis around 80% of homes are inadequately insulated, and about 25% of Minneapolis homes have no wall insulation. Heating and cooling represents 60% of an average single family home’s utility bill. This means upgrades related to heating and cooling provide significant opportunities to reduce the energy we consume, as well as to lower our bills. Second, ice dams can lead to water damage in your home. The meltwater builds up above the dam on your roof and eventually penetrates through the roof and into your house. Third, ice dams cause a lot of wear and tear on the roof shingles which can mean your roof needs replacing sooner that it ordinarily would.

The best way to prevent ice dams is to make sure the air temperature in your attic is the same as the air temperature outside all winter long. To do this, you must air seal your attic by sealing up any gaps in the attic (for example, from running wires or plumbing up through the ceiling). After air sealing, you must insulate your attic. Air sealing and insulating the attic will improve the temperature consistency in your home making it more comfortable throughout the year. Your energy bills will also be lower all year round because the insulation will keep the heat inside in the winter and the cold inside in the summer. Lower energy expenditure reduces your home’s environmental impact.

If your home needs air sealing and insulation, right now is a great time to get it done!  CenterPoint Energy provides a rebate that covers 30% of the project cost (up to $500 for each project). And If you live in the Tangletown neighborhood, while funds last, the Tangletown Neighborhood Association will match one of the CenterPoint Energy rebates for double the incentive. That’s up to $1,500 towards your project! The City of Minneapolis is also offering 0% financing on these improvements. To get started, we recommend scheduling a Home Energy Audit to learn whether insulation or attic sealing is the right choice for you. Contact or 612-244-2484. If you’re ready to jump right into the attic sealing and insulation improvements, make sure to select a rebate eligible installer. Visit for more information on our rebates.

Happy New Year, dear readers! Let’s make 2020 the year of reducing greenhouse gases and eliminating unnecessary plastic and waste!

Sustainability Sam

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