Ask Eartha: How to prevent ice dams and roof leaks
Dear Eartha, every winter the lower edge of my roof gets covered in a thick sheet of ice. Come spring, massive icicles form. How should I deal with this ice buildup?
Despite its nostalgic wintry appearance, an icicle is a telltale sign that a home is not performing several basic functions and, in some cases, can lead to roof leaks or failures. The common term is ice dam, a literal wall of ice that can dam melting snow from above and force water into your home. While ice dams and roof icicles are a common sight across Summit County, they are not inevitable.
Ultimately, the ice dam is merely a symptom of a deeper issue prevalent across much of our existing housing stock in the mountains. Many contractors will turn to de-icing cable, often referred to as heat tape, to apply heat directly to the affected areas. Contractors seem to have saved the day — until you see your utility bill.
The harsh truth about de-icing cable is that it uses a lot of electricity — about 6 watts per linear foot at 32 degrees and even more at lower temperatures. If 100 feet of cable is used for 6 months, it will consume more than 2,600 kilowatt-hours of electricity at a cost of $300. With the average Summit County home using about 9,800 kilowatt-hours for an entire year, this one appliance could account for roughly 20% of energy costs.
For this reason, we discourage the use of de-icing cable. If you already have heat tape on your home, consider installing a timer to run it from 6 a.m. to 6 p.m. and only when there is snow on the roof. It might seem counter-intuitive, but the best time to run heat tape is during the day when it’s sunny and the temperature is above freezing.
How ice dams form
When indoor heat is lost through the attic or vaulted ceiling space, it heats your roof and causes snow to melt. The melted snow trickles down your roof until it reaches the eave (the section of roof extending beyond your exterior walls). At the eaves, the melted water no longer absorbs the heat loss from the main part of your roof, so it refreezes and — voila — you have the beginning of an ice dam.
As more ice accumulates, it traps water flowing down the roof, trapping more water behind it. As these dams grow, icicles begin to form from excessive water flowing up over the dam. Ultimately, the water that remains trapped behind the dam can penetrate the roof and leak into the home.
The proper solution is to address the core cause of ice dams: indoor heat loss through the roof. I recommend improving your attic or vaulted ceiling insulation and maximizing the roof’s ventilation. What we are after is a roof temperature that matches the outdoor temperature. Therefore, the insulation in your attic sits down against your ceiling to keep the heated air down where it’s needed in the home. If you have cathedral or vaulted ceilings in your home, the solution remains the same. Ventilation baffles should be installed in your vaulted roofs, conducting outdoor airflow across the underside of your roof sheathing before it exits near the peak of your roof.
When I look out over the rooftops of my neighborhood, I can visibly surmise who has a well-insulated and ventilated attic simply by who has the most unmelted snow on their roof. This snow is a consistent thickness from the peak to the eave and will melt as one cohesive piece from natural conditions alone, rather than from heat loss through the home itself.
If you’re considering an energy-efficiency improvement for your home, or if you want to learn more about what can be done to reduce ice dams, you should start with an energy audit of your property. Have a certified building analyst inspect your home for potential safety concerns and energy efficiency.
Visit HighCountryConservation.org to request a home energy audit. You’ll receive a comprehensive report outlining areas for potential improvement as well as expected annual savings, and you’ll understand what it is your home truly needs.
Ask Eartha Steward is written by the staff at the High Country Conservation Center, a nonprofit organization dedicated to waste reduction and resource conservation. Submit questions to Eartha at firstname.lastname@example.org.
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