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Cathedral attic moisture

rotary82 | Posted in GBA Pro Help on

I have an attic converted to living space where the roof is also the cathedral ceiling. Most bays go from soffit to ridge and are insulated with fiberglass and a foil barrier with a Duravent installed so that there is always an airspace from soffit to ridge. Those bays are mostly fine. The areas I’m having a ton of ice and moisture on the sheathing is where the bays are interrupted and there is only a ridge vent. Should I fill the bays solid with spray foam? Or should I at least foam up the ridge vent from the inside on those bays? If I do a perfect job with the foil barrier will that stop the moisture from getting into the bays? I have a damp basement and as much as I want to seal it up it is no way in my price range.

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Replies

  1. DickRussell | | #1

    Here are a couple of links for reading:
    https://www.greenbuildingadvisor.com/blogs/dept/musings/how-build-insulated-cathedral-ceiling
    https://www.greenbuildingadvisor.com/blogs/dept/musings/prevent-ice-dams-air-sealing-and-insulation

    What is this "foil barrier" you mention?

    If you have a damp basement, that moisture will migrate upward in various ways and continue to cause problems. It needs to be fixed. Here is another "how to" article on that:
    https://www.greenbuildingadvisor.com/blogs/dept/musings/fixing-wet-basement

  2. rotary82 | | #2

    Thanks for the links. I have a 1929 stone foundation. Water makes its way through. I have installed new gutters and sloped the surrounding material away. The problem is the 'bolders' the builders left against the house mixed with a sandy gravel let's the ground water migrate to my basement. I have a french drain installed and the water makes its way out of the basement but leaves it damp. As far as the foil wrap it is the Prodex Total 1/4" insulation that also acts as a moisture control.

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