I have massive ice dams building up on my roof. How important is it that I take care of these, and if it is, how do I avoid ice dams in the future? — Beth, Dillon
We’ve been hearing quite a bit about ice dams this winter from a number of Summit County residents. In fact, I’m especially qualified to respond to your ice dam inquiry as I too am in the throes of an ice dam war.
Often considered to be an unavoidable staple of winter dwelling in our mountain community, ice dams have a reputation for being that building concern we tend to avoid addressing. Perhaps it’s a childhood fear of icicle impalement, but I rarely run across those brave enough to attack ice dams at their roots, in fact most people I come across avoid eye contact with them all together.
It’s important to first understand that ice dams do not have to be a mandatory adornment on your mountain home. You can still fit in with most social circles without these massive ice blocks on your roof.
Secondly, ice dams are a serious building concern that should either be mitigated or addressed at their root cause. Much like an effective medical practitioner, energy analysts and building scientists would agree that the proper way to address an issue is to solve the core problem. Rather than prescribe a solution to the symptoms of a problem, we always strive to solve the problem itself.
Many contractors will turn to deicing cable, often referred to as heat tape, to solve this symptom. Installing several hundred feet of deicing cable on the lower sections of your roof, these contractors seem to have saved the day.
This holds true for most, until they see their utility bill. The harsh truth about deicing cable is that it uses a lot of electricity — about six watts per foot at 32 degrees F and even more at lower temperatures.
If 100 linear feet of cable is utilized for six months of the year, it will consume more than 2600 KWh of electricity at a cost of $300. For this reason, in addition to it being a mere symptom fix, we cannot in good conscious recommend installing deicing cable. There are two actions that cause snow to melt on roofs.
The primary action is caused when indoor heat is lost through the attic or vaulted ceiling space causing snow to regularly melt on the roofing surface.
When this migrating water reaches the eave it is no longer exposed to the indoor heat loss from below. In fact, this water is now extended over a section of roof that is much colder than the sections above. At the eave, the water refreezes and ice accumulates, creating an ice dam that can trap water behind it. Ultimately, the water that remains trapped behind the dam may penetrate the roof and manifest as a leak within your home.
The secondary action that causes snow to melt on roofs is sunlight and warmer temperatures. This action however typically affects the entire roof area including the eave, and is less likely to create an ice dam, unless of course an ice dam is already present.
The proper solution to the core cause of ice dams is to reduce indoor heat loss through your roof. We recommend improving your attic or vaulted ceiling insulation so that on-the-roof deicing cable may no longer be needed. What we are after is achieving a roof temperature that matches the outdoor temperature at all times.
This is why the insulation in your attic sits down against your ceiling and the roof remains bare material and why your attic is cold when it’s cold outside. We desire our attics to be properly ventilated, reducing the propensity for condensation to build up and other building durability issues to arise. 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. Then we like to densely pack the vaulted ceiling with insulation until the cavity is full.
If you must use deicing cable for safety reasons, consider installing a timer to run the heat tape from 6 a.m. to 6 p.m. and only when there is snow on the roof. It may seem counter-intuitive, but the best time to run heat tape is during the day when it’s sunny and the temperature is above 32 degrees Fahrenheit.
If you’re seriously considering an energy-efficiency improvement for your home, or even if you want to learn more about what can be done to reduce the ice dams on your home, you should start with an energy audit of your property. Have a certified building analyst audit your home for both potential safety concerns and energy efficiency. Visit EnergySmartColorado.com to request a home energy audit at your property.
The most important first step in solving any problems at your home is education. Through a home energy audit, you’ll understand what it is your home truly needs.
Ask Eartha Steward is written by the staff at the HC3, a nonprofit organization dedicated to waste reduction and resource conservation. Submit questions to Eartha at firstname.lastname@example.org.