Damn Ice Dams

This winter may go down in history as the ‘winter of the ice dam’.

The snow fall has been dramatic and the freeze/thaw cycles have created situations conducive to ice dam formation. Many houses in Western MA are experiencing the wrath: damaged gutters, roofs, and most severely, water leakage to the interior of the house. The effects of ice dams are clear and painfully understood. However the cause of ice dams, and the proper solutions, are poorly understood.

Simply put, ice dams are ridges of ice and icicles formed by melt-water high on the roof re-freezing lower on the roof. The result is a recursive build-up of ice that can result in water entering the roof. Difference in temperature from the high part of the roof causes ice dams. The most common causes of this: 1. Under-performing insulation, or thermal bridging 2. Air leakage from house entering the unconditioned attic space. 3. A source of heat such as a poorly insulated duct in the attic. 4. Flawed soffit ventilation that compromises insulation 5. A difference in snow thickness with solar heat gain.

The common theme of the above causes is heat that is meant to be warming the people inside the house, is instead warming the underside of the roof deck. Even in buildings with lots of insulation, there can be dramatic ice damming. This is due to the lack of a proper air barrier, a very important component of the attic insulation boundary. Simply adding more insulation without air-sealing penetrations in the attic flat, may not solve the problem.

Another common misconception is that adding more ventilation is a good way to solve ice damming. This could work because it cools the attic, keeping the roof cold, yet it is much more practical to do a good job limiting heat from leaking into the attic, than to remove it once it is there. Heat is expensive, keep it in the house! Unconditioned attics do need proper ventilation to manage moisture, yet poorly installed soffit ventilation is all too common and can contribute to more heat loss instead of effective ventilation.

The short term, temporary fix:

-remove snow and ice from roof.
-install electrical heat tape. Caution: can be very expensive due to electrical consumption.
-contact your insurance company. Take lots of photos

Lasting solutions. Fix it once, fix it right:

-have a qualified contractor diagnose and fix the attic thermal boundary. Ensure your contractor understands the importance of a proper airbarrier and of proper insulation and ventilation techniques. A ‘home performance contractor’ is likely to have the experience and proper skills to best address ice damming issues. Qualified professionals can be found at BPI.org, (Building Performance Institute)

Destructive ice damming is a symptom of a flaw in the building’s insulation boundary. It is wise to plan on properly fixing the root causes of ice damming, instead of employing ‘band aid’ fixes year after year. A proper attic solution will give piece of mind, and keep you cozier and energy bills under control.