Ice Dams are a serious problem throughout Canada, although it varies from year to year as to which region gets hit. Here we visited one of the solution companies who work to seal up the primary cause of ice dams, the warm air leaks into the attic. For more background on the problem check out this link to "Ice Dams".
Basically ice dams and icicles are caused by heat in the attic melting the bottom of the snow pack on a day when it is slightly below zero outdoors. Although good attic ventilation will help to alleviate the problem by cooling the attic, research has shown that the primary source of the heat, air leakage into the attic from the house below must be blocked off. Then you have to be sure that there is adequate insulation between the heated part of the house and the attic. Then that ventilation is capable of taking care of the little heat that we just can't stop.
ZeroDraft is a company in Mississauga, Ontario that uses foamed in place polyurethane foam to seal off those air leaks, even to provide insulation when necessary. When they do an inspection of the house, they start down below and check out things like the attic hatch (weather-stripped and latched down), electrical boxes in the ceiling, even plumbing openings that lead to the attic.
In the attic they actually seal off the cracks that are found at the top of every inside wall. They seal around the plumbing stack. For many stacks, like the one in the photo, this is about the only practical way to seal off this almost impossible to reach hole to the basement.
If you are changing the shingles on your roof, this is a perfect time to remove a couple of roof boards and use foam to seal the top of the outside wall. When the workmen have great access to this difficult area, they are able to seal the air leaks from below, insulate the top of the wall and create a rigid baffle to let the ventilation air in from the soffits -- all in one operation. For someone with ice problems who doesn't want to rebuild the entire roof, this is a great opportunity to fix the problems.