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Ceiling condensation

Syria | Posted in General Questions on

I have a client with an addition built in the late 1970’s. It is one large room.
The roof was built with 2×6 rafters, foil faced fiberglas insulation, skip sheathing, standing seam terne metal and no ridge vent. One side has a low slope (3/12?).
There are condensation issues on the drywall ceiling and possibly under the roof metal. The roof needs replacement and we wondered if a smart upgrade would be to install some rigid insulation on top of the roof sheathing, or would there another upgrade that would be a better way to solve the problem before the new metal is installed?

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Replies

  1. Expert Member
  2. Syria | | #2

    4A Virginia
    Sorry not to have included that.

  3. Expert Member
    DCcontrarian | | #3

    I suspect you might find the sheathing is ruined too.

    This is the definitive article on insulating unvented roofs:
    https://www.finehomebuilding.com/project-guides/insulation/five-cathedral-ceilings-that-work

    I wouldn't put rigid insulation over skip sheathing, it needs to be a continuous airtight layer. I think you could put insulation directly over the rafters and then run skip sheathing over that. I'm trying to think of a reason why you couldn't.

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