Last Updated: Jun 26, 2020
It's an iconic look, and one familiar to those of us living through northern city winters: scores of long, dagger-like icicles hanging from the eaves of our homes. Iconic or not, however, icicles of this magnitude often signal a severe problem: ice dams.
An ice dam is ice that forms at the edge of a roof and prevents water run-off as snow melts. Water back up caused by ice dams can result in damage to walls, ceilings, insulation, and other areas.
Ice dams can occur shortly after heavy snowfall. As warm air in the attic heats the roof, snow begins to melt, causing the snowmelt to run off. Once the run-off water reaches the roof's edge or eaves, mounds of frozen ice and icicles start to form, creating a dam. Untreated, ice dams will continue to grow as more snow melts and begin to run off.
Attic heat primarily comes from the house underneath it. One way heat in a home can reach the highest parts of a roof is by escaping through under-insulated ceilings. For example, the temperature rises and escapes a room through ceiling light fixtures, say, or spaces around ductwork or a poorly insulated attic. Similarly, exhaust systems placed along the roofline can add heat, and chimneys can contribute heat to attic space as well.
The trouble comes with the resulting heat gradient, where heat from an under-insulated ceiling rises into an attic. That heat warms up the roof, while eaves stay cold due to exposure to the elements outside.
The consensus seems to be that thoughtful prevention is more useful than some stop-gap measures. Especially when you have water dripping from your living room ceiling.
The U of MN Extension agrees with the "immediate action" of removing snow from the roof with a special snow roof rake or push broom. On a relatively warm day, hose the roof with lukewarm tap water, working up from the lower edge of the dam to make channels through it for water to flow off the roof.
Ridding yourself of ice dams is not as challenging as you may think, but it does require some work. The key is to keep the eaves and roof the same temperature. This can be accomplished by adding ventilation, sealing troublesome air leaks, and increasing insulation under the roof.
In our Top Four Tips on How to Insulate Your Attic, Tobias Roberts concurs with checking for air leaks and covering up cracks. He notes that "while many people spend much time sealing their windows and doorways, much more heat generally escapes from a home through the ceiling." He then suggests searching for places in your attic where insulation is thin or non-existent. Since most homes don't have insulated attics, choosing a natural insulating product like blown-in cellulose, straw or hemp. Finally, he proposes improving attic circulation, in particular, to keep the attic cold enough to prevent ice dams.
Air leakage paths sealed between the house and attic space cuts down on heat loss. Increase ventilation, ceiling, and roof insulation to make more impact. If the proper steps, such as the ones mentioned above, are taken, you can quickly mitigate several known causes of ice dams. Mechanical ventilation is NOT a recommended solution to ice dams as it could create moisture and air pressure problems.
For negative pressure to occur in a home, the pressure inside the home must be lower than the pressure outside. Typically, this happens when more air leaves the interior of the house than is replenished from the outside. Problems can occur because the relative vacuum inside the home causes air to be pulled in, sometimes from undesirable sites, like crawl spaces, attics, and basements. Consequences lead to diminished indoor air quality, including radon contamination and carbon monoxide poisoning.
Here is one last warning from your snow specialists in Minnesota. If a homeowner reduces the temperature gradient on their roof, and the whole roof becomes colder, significantly more snow can pile up. The snow load that the roof has to carry will increase because the snow no longer melts. While the U of MN extension service suggests most homes built to current codes will have no problem, it may be prudent to investigate nonetheless.
Fixing the ice dams is expensive. Insurance.com reports that the average homeowner's insurance claim for snow and ice damage is $4757. Online quotes are as much as $475/hour with a four-hour minimum. Prevention isn't necessarily cheap, either, however. A roofing cost calculating website includes the cost of 14 preventive measures. From caulking and chimney flashing ($5 to a few hundred) to blown-in insulation (average price $700-800). To a ventilation upgrade ($1500-2000 for a new ridge vent) and buying your steam pressure washer to melt the dams, as professionals often do ($4,000-10,000).
Avoid the higher costs of repairing the potential damage inside your home. Your best bet is a budgeted, step-wise plan for ice dam prevention: sealing, insulation, and ventilation.
Donna Pols Trump’s work has been published in literary magazines and online. She has received several Pushcart Prize nominations. Donna’s education includes degrees in Biology and Physical Therapy and a host of writing classes taken and taught at The Loft Literary Center in Minneapolis. Her short story “Portage” was selected by judge Anne Tyler for first prize in a 2018 contest sponsored by december magazine.