Those long, beautiful icicles dangling elegantly from the edges of your roof are very pretty to look at. But they are also an indication of potentially damaging ice dams.
An ice dam is caused when snow on your roof melts from escaped heat from your attic. Rather than just running off the roof, the water freezes again and forms a layer of ice under the snow, right at your eaves. As the process continues, the ice grows and can work its way under your shingles and eventually even cause a leak. The freezing and thawing pattern can force shingles apart, push eaves troughs away from the soffits of your home and wreak havoc.
The solution to destructive ice dams is usually more, or better, attic insulation. Your home’s attic should be considered “outdoor” space. That is, it should not be heated or cooled. You want your attic to be well ventilated and stay dry. You should never vent your furnace, dryer, or any fans into your attic—that can cause rot.
To keep your attic cold in the winter, you need to make sure your home’s warm air stays in your home and doesn’t escape into the attic space. Attics in Ontario should have between R49 and R60 of insulation, according to EnergyStar (http://www.energystar.gov/?c=home_sealing.hm_improvement_insulation_table). Blown in cellulose insulation is economical and efficient, although batt insulation also works fine. Sprayfoam is highly effective providing not only insulation, but also draft proofing, but is definitely a professional project and can be costly.
Government grants may still be available for insulation, so it’s worthwhile to check before you begin work.
Insulate your attic well and provide airflow for ventilation and you’ll solve those ice dams for good.