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Why Do Ice Dams Form On My Insulated Roof?

  • Transcript

    LESLIE: Alright. Jeff in Michigan is on the line with an ice-damming issue. How can we help you?

    JEFF: We have a house that was built 20 years ago. It’s a Cape Cod. And on the front part of the house, during the cold season when we get snow and ice, it seems to be building up ice dams in the front. And it has, oh, probably 18 inches of insulation in the upstairs. So I’ve even tried the electric heat tape to try cutting it back and it still seems to ice up. So I’m just trying to figure out what I can do to solve that problem.

    TOM: OK. So the insulation, does that sort of get pressed right up against the underside of the roof sheathing? Or do you allow ventilation to pass over the top of the insulation?

    JEFF: What it does is they have Styrofoam ducts up to it, down to the front of the fascia.

    TOM: Is there ventilation in the soffit areas that air can pass over that? Because the problem here is this, alright: heat is passing up through that insulation and it’s warming the roof directly above it. And as a result, the overhang is staying super cold, so it’s freezing there and causing that dam to build up. If you have proper ventilation where the air is getting into the soffits, running up underneath the roof sheathing and out at a ridge, that will protect against ice dams. That’s all you can do, really, inside.

    From the outside, do you – have you had to do any repairs as a result of these ice dams? Have you actually gotten water leaks or anything like that?

    JEFF: No, we have not.

    TOM: Because if you do, the good news is that they’re covered by homeowner’s insurance. And if that was the case, I would have that portion of my roof removed and make sure I have ice-and-water shield installed, up 3 or 4 feet from the roof edge, to make sure I never got any leaks in there again.

    JEFF: OK. Alright.

    TOM: So I would take a look at the insulation, make sure you’re getting good ventilation above it. And if it does happen again and you ever get a leak, call your homeowner’s insurance agent, get a claim filed, and then have ice-and-water shield put in so it never happens again, Jeff.

    JEFF: OK. Great. I appreciate it.

    TOM: You’re welcome. Good luck with that project. Thanks so much for calling us at 888-MONEY-PIT.

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