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Community and Q&A

Foaming a low-pitched roof

hughsdb | Posted in Energy Efficiency and Durability on

I have a 4/12 roof that is being converted to an unvented attic. The foam subcontractor assured me that he could get foam, being sprayed on the underside of the roof, to the plate line. He finished the job assuring me that they had been successful.

I drilled holes and used a scope to see the void that extends out to 6 -10″ from the exterior wall plates. How much of an issue is this?

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  1. GBA Editor
    Martin Holladay | | #1

    That's a crucial area where insulation is required if you want to prevent ice dams. (Of course, I don't know your climate zone, so I don't know whether you have to worry about ice dams. But even in a warm climate, this uninsulated thermal bridge will lead to undesired heat flow.)

    I don't know whether you have any paperwork that specifies the scope of work. Ideally, your understanding that the contractor "could get foam being sprayed on the underside of the roof to the plate line" was put into writing.

    If that understanding wasn't put into writing, that doesn't mean that the contractor is off the hook. Leaving an uninsulated void doesn't meet anyone's idea of an adequate insulation job. So ask the contractor to return to the job site to formulate a plan for insulating this void. Hopefully, the contractor is honorable, and there will be no dispute.

  2. hughsdb | | #2


    Thanks for your reply. We are in Climate zone 2 so ice dam is not an issue. However, as this is a hot humid climate, moisture is. Of course this is also a rather large area of thermal bridging. At this point I think that he would like to do the right thing. I'm just trying to determine what I need to push for. I want to provide him, and myself, with a sense of how critical this is. I have been putting off getting a thermal camera. It may be time to make that purchase. This may provide a good write up.

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