THE CURE BECOMES THE CAUSE!
Often touted as a cure for ice dams, roof raking often creates ice dams in worse places. Roof raking accomplishes its best results when all of the snow can be removed from the roof. Only removing a portion of the snow can create problems further up - beyond any ice water barrier underlayments. Why is this so? The common wisdom is that ice dams only form over the cold eaves of a house because the roof over the heated portion of the house is warmed by heat escaping from the house. Freezing occurs at the eaves because the eaves are extended beyond the heated portion of the house. It has been easy for the 'experts' to make this claim because ice dams at the edges have been something we all have been dealing with for decades. It doesn't take long when fielding calls from homeowners who are experiencing ice dams after roof raking to understand that ice dams can form even over the 'heated' portions of the roof. This occurs when the snow (which acts as an insulator) is removed and a 'cold' edge is created. Notice the picture to the right. Do you see the ice dam forming in the valley. This will continue to build and possibly cause a leak. After a recent 15-20 inch snow fall over much of Vermont in 2012, we have been able to observe this happening time and again.
Does roof raking prevent ice dams at the gutter edge?
Roof raking can prevent ice dams when snow fall is lighter and the temperatures are right. However, when snow fall begins build on a roof, the resulting snow melt can refreeze on the raked area and build at the bottom. Of couse, removing the snow from the roof is a good idea to prevent collapse from heavy snow loads. But, we rarely experience those types of snows here in Vermont. During the winter of 2006 we ran a roof top snow removal campaign because there was a lot of snow that winter. A large part of the business that winter was from customers who roof raked 3-6 feet up the roof and caused ice dams both up the roof and in the gutters. We would visit the home, remove all of the snow from the roof and melt the ice dams. Without that complete removal the ice dams would continue to build. That is what we are seeing again this year - roof raked roofs with ice dams. Consider the extended view of the picture from above. There are ice dams forming at the gutter and the entire roof is covered by a sheet of ice. There is still much winter left and these dams will continue to build.
What can be done?
Our experience with ice dams has led us to the conclusion that you should first deal with the heat loss. Air sealing is the practice of sealing areas where air can leak into the attic space from your heated living space. Without doing this, no amount of insulating will help. Many homeowners skip this step because of the expense of doing this right. Obviously, then, insulating is the next step. A recommended level of R-40 to R-60 should be installed. We favor cellulose over chopped fiberglass for blown insulations. You can do your own research on that. Icynene (or spray foam) is the best as it performs both air sealing and insulating at the same time. Ventilation can also play some role (it is absolutely necessary for the summer time health of your roof). Sometimes, these measures are impractical, overly expensive, or ineffective. If that is the case, our roof and gutter ice dam prevention systems will safely and effectively prevent ice dams. We would be happy to design a system for you.