I’m looking for preventive medicine in the design of a new hip roof (with asphalt shingles) for my house. I’m intending to have very deep overhangs (about 2′-6″) but I’m in the Chicago area and am worried about ice damming.
What are the range of solutions?
I was considering using two or more inches of rigid insulation over the sheeting so that the surface temperature of the shingles would not be warmer over the house than over the eave. That might help avoid the problem, however, if I used the rigid insulation I would then have to sheet over it to provide a nailing surface for the shingles. Also, it complicates the facia condition.
I’m open to suggestion.
Tony
Edited 3/28/2002 3:52:20 PM ET by Tony
Replies
Dear Tony,
I would discourage you from pursuing that strategy, even though it may be effective. We are set to see world petroleum production peak in 2004. This is going to be a big deal, so I'd like to see as much insulation used to it's highest potential.
You want to keep heat from the house away from the roof. Put all your resources into making a thermal barrier exactly b/t the indoor and out door spaces. This usually means creating an effective air seal and insulation layer right on top of the ceilings.
You'll get protection from roof ice. But the insulation and air barrier will also lower your fuel consumption.
Conservatively, Fred
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Plenty of insulation and a cold roof. A cold roof is a layer of 2x's running from the eaves to the ridge or hips on top of the regular sheathing. This air space is covered with another layer of sheathing and then shingles. This space is vented top and bottom. This can complicate existing roof trim but is a good solution for new construction.