Are roof de-icing cables an effective way to prevent ice dams?

A common problem for homeowners in snowy climates is the formation of ice dams on their roofs.

Ice dams are build-ups of ice and snow on the edges and eaves of a pitched roof. Ice dams can result in beautiful icicles, but they can also damage the roof, break gutters and cause water infiltration.

Several strategies have been developed over the years to prevent the formation of ice dams and the resulting property damage. One of the most popular strategies is roof de-icing cables.

In this article, find out how ice dams form and how roof de-icing cables can help counteract the process.

What causes ice dams?

After a heavy snowfall with temperatures below freezing, roofs can be covered with a thick layer of snow. Ideally, the roof’s temperature should be the same as the ambient temperature outside, so that the snow covering the roof will melt at the same rate as the snow outside the thermal bridge. (See diagram)

However, it is common for heat in a home to seep into the attic through the ceiling due to a lack of insulation. If this occurs and the roof is not properly ventilated, it will become warmer than the temperature outside, and the bottom layer of snow in contact with the roof will melt. On pitched roofs, the melted snow will then flow down the roof underneath the upper layers of snowpack.

Roof edges tend to be colder than the rest of the roof, because they are suspended over cold air rather than covering the house that is leaking heat. When the melted snow reaches the colder edges, it freezes and blocks the flow like a dam. The mound of ice grows over time and can reach a significant size quite quickly, particularly if the gutters are obstructed.

As the ice dam grows, it prevents water from draining properly off the roof. With nowhere else to go, the water may seep between the shingles and into your home. Roof leaks can damage the roof structure and insulation and cause harmful mould. Ice dams can also damage gutters and create hazards for people and animals walking underneath them.

How can roof de-icing cables help prevent ice dams?

Roof de-icing cables use electrical resistance to generate heat, melting pathways through the snow and ice on the roof. The channels allow meltwater to flow off the roof instead of freezing into ice dams or seeping into the roof.

De-icing cables cannot melt all of the snow on the roof or completely prevent ice dams. Roof snow removal is still important when there is a thick layer of snow, even if the roof is equipped with de-icing cables.

Advantages of installing roof de-icing cables

If the de-icing cables are good quality and are installed by certified professional roofers, they can certainly minimize the water accumulation that causes ice dams and help slow their growth. They are generally placed in patterns along eaves, around chimneys and skylights and in gutters or drainpipes.

Although de-icing cables aren’t a permanent solution, they are an excellent choice for homeowners who need a quick solution. They cost much less than the roofing work needed to seal attic leaks, install proper insulation and create appropriate roof ventilation systems.

What to know before installing roof de-icing cables

Roof de-icing cables run on electricity. If you leave them running all winter, you will definitely see a slight increase in your electricity bills.

Remember that de-icing cables address the symptoms, not the cause of the problem. They are not infallible—they can stop working due to issues such as a short circuit.

Les Couvreurs Duro-Toit specialize in installing roof de-icing cables

It’s very important to understand that roof de-icing cables cannot prevent ice dams from forming or eliminate them completely. They simply melt channels through the dams to help meltwater flow off the roof. To prevent ice dams from forming in the first place, you must address the root of the problem—an overheated roof caused by heat leakage from inside the house and/or a lack of maintenance in specific weather conditions.

Thankfully, les Couvreurs Duro-Toit are here to help homeowners whose roofs are prone to ice dams. After inspecting the roof, they can suggest a customized approach that includes all of the work needed to keep your roof at the ideal temperature.

Contact us for more information!