The first winter in our house wasn't bad---temperatures and snowfall lingered around normal and snow often melted within a week or two of when it fell. My major concern was reducing our heating bill. Since then, we've replaced a leaky window, removed a leaky in-wall, window-style A/C, and added insulation to about 1/2 of the house walls. These improvements have helped reduce our oil usage by about 25%. But, I wasn't prepared for this year's surprise: ice dams.
This winter hasn't been so kind. We received about 6 feet of snow in little more than a month. And, for a span of 20 days and 4 1/2 feet of snow, the temperatures have stayed low enough that almost nothing has melted. The piles are high enough that's its getting difficult to clear my driveway.
Last Monday, my wife called me to say that there was water leaking into the house around a window. Ack! I knew we had significant ice build-up around the gutters, but I didn't think it was that bad. I scheduled an appointment for Thursday (since it was supposed to snow Tues & Wed) to have our roof cleaned and decided that I needed to do some roof cleaning myself. So, I dragged my shovel up on the roof with the help of my wife and I started shoveling. Four hours later, I had the roof mostly clean. I was afraid of damaging shingles and/or gutters by trying to break/remove ice, so there were still patches of ice on the roof and plenty of ice in the gutters, but I figured getting rid of the snow was at least a huge improvement. On Thursday, Willard cleared the snow that had fallen Tues/Wed and also cleared off much of the ice. After the recent warming and rains we've had, my roof is almost completely clear of snow and ice.
I knew that our low-pitch roof, cathedral ceilings and recessed lights contributed to ice dams. I now realize that skylights, vents and chimneys also contribute---anything that allows heat to come in contact with snow on the roof contributes to ice dams. This is the best article I've seen about ice dams. It provides a good explanation of how they form, why they lead to water in the house and how to prevent them.