Ice Damming

1/20/12 We have been blessed so far, but the snowy part of our winter has finally arrived. For those of us that suffer from "ice dams", it is time to keep up with the snow to prevent water from entering the house. As home owners, water is our enemy. 

If you are not familiar with the ice damming, it is caused by the unequal temperatures in the attic. Warm air from the house escapes into the attic and rises up to the ridge. Meanwhile, the air at the eve is colder. The snow at the top of the roof melts then freezes at the eve. This repetitive process causes a build-up of ice at the eve, creating a dam. The dam causes water to get up under the shingles and presto, you have water leaking out of your ceiling. 

In order completely resolve the issue, you need to check the insulation and the ventilation of your attic. A well insulated attic with the proper use of vapor barriers will help keep the heat and moisture inside your house.  

Then there is the more complicated issue of ventilation. Ideally, you would like to have good "ridge and soffit ventilation" where the air enters at eve through the soffit vents and gets expelled out through a ridge vent at the top of the roof. The installation of an exterior baffled ridge vent will draw more air in at the eves, resulting in a better flow of air through the attic, helping to maintain a uniform temperature between the eve and the ridge. An exterior baffled ridge vent uses the principles of Bernoulli's Law. Wind passing over the roof of the house creates high pressure on one side of the ridge and low pressure on the other, sucking the air out of the attic. In order to accomplish this more effectively, the area of the soffit vents should be 51% or greater then the area of the ridge vent. When converting an older home with gable ventilation (those big square or triangular vents on the sides of the house) to ridge and soffit ventilation, the gable vents should be closed-up so as not to disrupt the flow of air. Some older styler houses such as "capes" due to their construction are not conducive to adding soffit vents without major reconstruction of the roof to add insulation and "proper vents". In that case, there is a new product on the market called an "edge vent" which is cut into the roof at a point where the eve opens into the attic. For more information on Edge Vents, consult "Vent Master" located in Arlington, MA. 

Other methods used to resolve ice damming utilize the installation of "heat tape" along the exterior eves to melt the ice build-up or a snow rake to remove the first three feet of snow at the eve. For those of us who are experienced with ice dams, preventing them from forming is much easier then removing them later. So it's time to get busy. A couple ounces of prevention now, will save a ton of aggravation later. 

Best of luck this winter. If you have any questions, please feel free to email or call.