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Homeowner guide

Ice dams: the cause and the real fix

Ice dams are an attic problem that shows up on the roof. The permanent fix is air sealing, insulation and ventilation.

How an ice dam forms

Heat from the house warms the roof deck. Snow melts from underneath, water runs down the roof, reaches the eave, which hangs out over cold air, and freezes. The ridge of ice grows, water backs up behind it, and finds its way under the shingles and into the wall. Stained ceilings, peeling paint and wet insulation follow.

The fix is in the attic

  1. Air seal the ceiling plane so warm air stops reaching the roof.
  2. Insulate to R-49 or better so the little heat that does conduct through is slowed to a trickle.
  3. Keep the soffit and ridge vents open with baffles so outdoor air washes the underside of the roof and keeps it cold.

All three are standard NHSaves measures on a qualifying home: the air sealing paid in full, the insulation and baffles at 75%.

Ice dams every winter? Let us look at the attic.

We measure the attic, find the heat leaks with the infrared camera, and give you the fix and the rebate in writing.

Book an assessment(603) 555-0100

Questions

Why does my roof get ice dams and my neighbor's does not?

Heat. Your attic is warmer because house air is leaking into it and the insulation is thin, so the roof snow melts from below, runs down to the cold eave and freezes. The neighbor's attic is as cold as the outdoors.

Are heat cables a bad idea?

They keep a channel open so water can drain, which protects the house from the worst damage, but they use electricity all winter and do nothing about the heat loss causing the problem.

Does raking the roof help?

It removes the snow that would melt, so yes, as a stopgap. The permanent fix is in the attic, not on the roof.

Related

Attic insulation guideR-values and signsOur attic serviceAir sealing and celluloseDo I qualify?ZIP, fuel and square feet

Let's take a look at your house.

It starts with a phone call at no cost. We tell you plainly what the house needs, what NHSaves will cover and what the rest will cost, in writing, before anything is scheduled.

Book an assessment (603) 555-0100
Call (603) 555-0100