Ice dams are those sheets of ice and snow that form at the edge of your roof. They often look beautiful and result and in long, lovely icicles hanging from your eaves. I saw a lot of them driving around Medford.
I love looking at them and as a child I loved breaking icicles off our roof and sucking on them. They were nature’s popsicles. While these make a quintessential New England picture, they are actually quite bad for your roof and should be removed.
Ice dams are formed when there is freezing and melting on your roof. This is bad because as water freezes it expands. This results in the water getting up under your shingles, then when it freezes it expands, pushing the roofing apart and making bigger holes and degrading the quality of your roof. They repeat the same actions in your gutters, resulting in the gutters getting warped and deformed over time as well.
Ice dams frequently form when buildings do not have adequate air sealing. Attics should be air-sealed and insulated to prevent the heat from escaping into the attic. When warm air is in the attic, the portion of the roof over the warm attic is also warm, melting snow on the roof. However, the edge of the roof that hangs out over the wall is surrounded by cold air and is colder. When the melted snow runs to the edge of the roof it freezes creating a damn that holds more water above it. This water ponds and finds cracks in the roof that it would have otherwise run right over, and infiltrates into the attic and walls of the house causing water damage.
When attics are well sealed you don’t see ice dams as frequently because the air temperature is even under the entire expanse of the roof, so the water more easily runs right off the edge of the roof. It is still possible to get ice dams with a well insulated attic, but they are usually not as frequent or severe.
The best thing to prevent ice dams is to get your house properly air sealed and insulated. Medford residents can call MassSave/CSG at 855-838-7817 for a no-cost home energy assessment. The assessor will determine what air-sealing you need, and the company will schedule up to 8 hours of air sealing work for free. Please mention "Go Green Medford" when you call.
However, if you have ice dams right now, there is a safe way to get rid of them.
Fill an old stocking with calcium carbonate. If you can make it longer than the width of your ice damn, that is great, otherwise, a foot or two long is good. Tie off the end. Toss the stocking up on the edge of your roof, on top of the ice dam, such that it lies vertically up your roof and hangs off the edge a little. The ice will begin to melt under the stocking, creating a channel that will let the melted water above the ice dam run down. How far apart you space them probably depends on what the ice dams look like and how the water is ponding above it, but I’ve seen every 2 feet as a suggestion.
A stocking is better than a sock, because the material is thinner and you can make a longer tube. There are a variety of ice-melts out there, but calcium carbonate is most often recommended for this purpose. Salt is not recommended because its corrosive properties might damage your roof. You can also see in our picture how calcium carbonate worked quite well while rock salt and potassium chloride did not work well at all.
This was re-posted from Green Lifestyle Changes.