Will a new roof stop ice dams in Connecticut?

Short answer: not by itself. A new roof installed with the right eave protection limits the damage ice dams do, but the dams themselves come from the attic, not the shingles. The time to fix both is during the replacement.

How an ice dam forms

Hartford-area winters bring plenty of snow: the 1991–2020 average at Bradley International Airport is a little over 48 inches a season. When snow sits on a roof over a warm attic:

1. Heat leaking from the house warms the roof deck.
2. Snow on the upper roof melts, even when the air is below freezing.
3. The meltwater runs down to the eaves, which hang out past the warm walls and stay cold.
4. It refreezes there, building a ridge of ice.
5. More meltwater backs up behind the ridge and works under the shingles.

Shingles are designed to shed water running downhill, not to hold back a pool of it. That is why ice dams cause leaks into walls and ceilings even on newer roofs.

What the new roof should include

• Ice-barrier membrane at the eaves, bonded directly to the decking, extending far enough up the roof to reach past the inside face of the exterior wall. Many Connecticut building departments call for it, and manufacturers require it in cold climates.
• Membrane in valleys and around chimneys and skylights, where water and ice collect.
• Drip edge installed so meltwater drops into the gutter rather than behind the fascia.

What actually stops the dams

• Air sealing. Warm air escapes into the attic through gaps around light fixtures, plumbing and wiring holes, the attic hatch and the tops of interior walls. Sealing these is the single most effective step.
• Insulation. Once leaks are sealed, adding insulation to the attic floor slows heat loss.
• Ventilation. Continuous intake at the soffits and exhaust at the ridge carry away the heat that does get through. Baffles keep insulation from blocking the soffit vents.
• Ducting. Bath and kitchen fans must vent outside, not into the attic.

Low-pitched ranches, Capes with knee-wall attics and houses with complex rooflines are the hardest cases. On a Cape, the sloped ceilings in the second-floor rooms leave little space for insulation and airflow, and the solution may involve work from inside as well as on the roof.

Planning it with the roofer

Ask how the proposal handles ventilation, whether soffit intake will be opened up, how far up the roof the eave membrane will run, and whether air sealing in the attic is included or should be done separately before the roof goes on.

See also asphalt shingle roof replacement and the notes on low-pitched houses on the Newington page.