Snow packs on a roof as snow falls from the sky. In theory, it should melt away when the sun shines again, and flow down the roof as water. The fact that the roof is relatively warm from heat inside the house helps, But when the melt reaches the unprotected eaves it freezes again, forming a dam. So do deicing cables melt ice effectively at this point, or not?
Why We Should Stop This Ice Accumulating
The colder eaves may stop the flow of snow melt at this point. However, the moisture keeps coming down the roof surface from above, adding to the ice dam. Moisture backs up on the slightly warmer roof, and can penetrate the roof’s defences, increasing humidity in the roof space.
How Deicing Cables Tackle Ice Dams in Theory
Ice cables contain a flow of electricity running through them, although the resistance in the wires causes them to warm. This warmth transfers to anything cooler, including ice. As the ice warms, it melts and voila the ice dam is gone. Well that’s what happens in theory at least!
In Practice, Deicing Cables Only Partly Melt the Ice
If someone were to ask us, do deicing cables melt ice completely, we would probably answer ‘not to the extent that you might expect’. That’s because the cold ice absorbs the warmth from the wires quickly, so it only has a limited effect.
This is why deicing cables cannot completely clear snow from a roof. In fact, most times they only clear the snow immediately around them. Although this is better than climbing up on a roof with a shovel, provided the snow melt can flow past.
You may therefore still find ice dams forming elsewhere on your roof where the surface is colder. Adding supplementary wires will add to the cost of the installation, and the cost of operating the system. At this stage, you may be wondering, can I afford this?
So Are Deicing Systems a Good Idea or Not?
Deicing systems are not perfect by a long shot, However, they should help prevent moisture entering the roof space in winter, which has potential to be far more expensive. The trick is to do the job properly, so you have the maximum benefit for the least cost. Speak to Valiant Exteriors in Calgary, if you would like to know more about keeping your home warm and dry this winter.
More Information
How Poor Attic Ventilation Leads to Ice Damming