Ice dams occur when melted snow refreezes at the edge of your roof. Living in a cold climate, we have seen thousands of ice dams. Unfortunately, most people don’t do anything to put a stop to the problem until damage is done. If a roof is not properly insulated and air sealed, ice dams form, eventually leaking into the building through the roof or roof trim.
The extent of the damage done by ice dams depends on where they enter your home and how large the dams are. However, much of the damage damage is immediately noticeable: dislodged shingles, water stains on the ceiling, sagging gutters, peeling paint and damaged plaster.
Some damage is not as obvious and can go unnoticed for a long period of time. In the winter, hot air leaks outside through wire and plumbing penetrations and wall cavities. This can create a vicious cycle; the more heat lost from the home, the more ice dams form, the more it leaks, the more the insulation gets damaged. Not only do you have to pay to fix the damage, heating costs increase.
So what can you do?
There are two ways to control the damage ice dams bring. Either you can maintain the entire roof surface at ambient outdoor temperatures, or build a roof to prevent ice dam leakage. Cold roofs allow the cold air outside to work in your favor. Keeping the roof as cold as the outdoor air solves the ice dam problem. Sloped metal roofs, however expensive, are slippery enough to shed the snow before it can melt and freeze.
You should also make sure to have proper ventilation, insulation and an effective blocking of air leakage. You can seal any ceiling leaks with caulk, packed cellulose or weatherstripping. Whichever way you decide to treat any ice dam damage, make sure to do it promptly to prevent additional damage, and call Showalter with any questions or concerns about your roof.
Courtesy of UMass Amherst
http://bct.eco.umass.edu/publications/by-title/preventing-ice-dams/
