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mcoomey
Ice Dams on roof without a soffit
mcoomey

What is the ultimate spare-no-expense solution to ice dams? After several years of roof raking and ice dam chipping I’m ready to bite the bullet and fix it correctly.

My house does not have soffits. The rafters just end at the sidewall, so soffit vents are out. I have ridge and gable vents, but w/o the soffit vents there's not much airflow. The ceiling joists are 2x6's so there's not much depth for insulation.

I was thinking about spray foam insulation on both the attic floor and against the roof. Would that cause ventilation problems? I used it on an addition that has a cathedral ceiling and have not had a problem with it in the 8 years since it was built.

keith3267
Re: Ice Dams on roof without a soffit
keith3267

You need good wall insulation first so that the wall doesn't transfer a lot of heat to the top plate and then radiate up to the eves of the attic. I do not see any reason why, if you use a closed cell foam, that you could not fill the whole cavity formed at the eve between the top plat of the wall and the underside of the roof. I would not go up the roof any more than necessary, but come into the attic far enough to where R-38 batt insulation can take over. That depends on your roof pitch.

Something else that might help in addition, crown molding. But on the exterior walls, wee if you can get triangular pieces of insulating foam that would just fill the gap behind the molding. That would also help to keep the area just above it warm. You might have to cut the foam yourself. If it doesn't help, at least your room will look better.

MtMan54
Re: Ice Dams on roof without a soffit
MtMan54

Hi, Ice dams are caused by heat loss in the attic. You can vent this lost heat to the outside or add enough insulation to keep the heat inside the house. The only way to add enough insulation to keep the heat inside the house, you need to reframe the roof so the full depth of insulation is over the walls. Reframing the roof so it can be properly insulated will lower your heat bills enough to pay for doing the work. Thanks

rhd1953
Re: Ice Dams on roof without a soffit
rhd1953

After putting a new roof on my 1924 house in the Quad-Cities(Iowa/Illinois at I-80) I spray foamed the underside of the roof sheeting to the depth of the rafters. My roof had no soffit or roof vents.

Spray foam is not cheap, must be correctly applied, but it does make an air tight seal at all locations, esp. the roof/outside wall joint.

If you spray foam the roof you must not have a vapor barrier on the attic floor, the attic is now part of the building thermal envelope.

I can email some pdfs of unvented attic assemblies/insulating unvented attics with spray foam and my attic before/after.

Now the attic is very quiet and there is no condensation on the under side of the spray foam.

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