It’s that dreaded time of year again when our worst insulation and air-sealing fears materialize as ice dams on our roofs. Ice dams are common with inadequately insulated and air-sealed homes in cold climates, and they can be the culprit behind major problems. This slide show provides all the information you need to know about what causes ice dams and how to prevent them.
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In the winter, ice dams form on many homes in the northern part of the country. While the water leaks that they may cause are often attributed to poor attic ventilation or to a roof in need of repair, the more common culprits are air leaks and insufficient insulation. Senior editor Martin Holladay explains how ice dams form and how they can be prevented.
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Find out why ice dams are a sign of an inefficient house
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Proper insulation and roof ventilation can stop ice dams from forming, prevent damage and lower energy bills
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Prevent Ice Dams with Air Sealing and Insulation
Ice dams form when a home’s escaping heat warms the roof sheathing and melts the underside of the snow layer on the roof. Water trickles down the roof until it reaches the cold roofing over the eaves, where it freezes. After a while, the ice at the eaves gets thicker and thicker, forming an ice dam. Eventually, water backs up behind the ice dam.
Learn more -
A Crash Course in Roof Venting
Understand when to vent your roof, when not to, and how to execute each approach successfully
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Summer is the Time to Head off Ice Dams
Summertime repairs to roofs damaged over the winter won’t do much good unless the underlying causes of ice dams are identified and corrected.
Read more -
Preventing ice dams in valleys
Get expert advice how to prevent ice dams in valleys
View Comments
Dear Martin: This slideshow on ice dams is helpful, but omits a key cause and cure -- like every article I have read on this subject. In addition to the typical culprit, inadequate insulation and heat transfer through the attic to the roof, ice dams can also be created on a tight and well insulated roof. Ours is insulated by ~10" of spray foam, for example, but ice dams can still form along the eaves. How? The sun melts snow on the dark asphalt shingles, which runs down until it reached the eaves and gutters which are slightly colder -- where the melt water freezes. The little dams grows, until -- voila! -- leaks occur. The only reliable solution: ice & water shield along all eaves and valleys, under the shingles. I recommend 6' in cold, snowy climates instead of the usual 3'. When we recovered our roof, we covered the entire surface with Grace Ice & Water Shield. This sealed the entire roof, and the additional cost was minimal.
Ice & water shield is no substitute for good insulation, but is the only real solution to costly leaks from ice dams.
Mark