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?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
What is your climate zone?
https://beta.greenbuildingadvisor.com/app/uploads/sites/default/files/images/DOE_climate_zone_map.preview.jpg
https://www.greenbuildingadvisor.com/article/all-about-climate-zones
4A Virginia
Sorry not to have included that.
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.