ICE, a CANADIAN WINTER DILEMMA!
This is a century old home with a huge attic. As you can see the existing insulation is uneven and missing in different cavities. Also, debris has been left by previous trades. This house was built at a time when insulation was non existent. All along the edges of the roof the brick work is built up right into the soffit, not allowing for lower ventilation of the roof. Despite this, the attic has more than adequate upper ventilation and a voluminous attic space because of the steep roof.
Also, the amount of insulation is less than desired. Resulting in a R-value between R-20 and R-30. In part of the attic there were areas that had been worked on by mechanical contractors over the years where insulation was removed to get other work done and not replaced properly. This resulted in massive amounts of heat hitting the under side of the roof deck and shingles which resulted in a huge ice build up. Notice also the single wall non-insulated ventilation pipe for the bathroom fans which causes condensation inside the pipe and heat loss into the attic as well.
Note in the image above how openings caused by rodents, such as mice, will reduce the effectiveness of your insulation as well.
Here is the same attic after the insulation has been blown in. Also a new insulated pipe has been connected to the roof exhaust vent. To your left the image shows how much extra insulation was put on top. This attic now has R-50+ and ice damming will be reduced significantly.
These image is from another roof where ice build up has been an issue as well. In this instance it was decided to replace batt insulation with layers of foil faced foam on certain sloped areas to increase the R-Value to R-50+.
Over the years at Huyvan Home Improvement, we have worked with a lot of different houses with different roofs and different issues. Each home has its own distinct character based on the time of construction, material used and building techniques. Hopefully this information has given you some informative tips on how to deal with those ice problems that are so common in our climate today.