Vented flat roof
I’m trying to find the best way to insulate my vented flat roof. I’m in Wisconsin, zone 6b. I’ve demoed my living room down to the studs. I’m planning to replace the roof in the next 5 or so years, with a non vented roof with insulation on the top of the roof decking. However, in the mean time, I’m trying to come up with a cost effective solution.
I have a modified bituman membrane and shiplap roof decking. The membrane is in good condition. I foolishly coated the roof with a elastomeric sealant before I knew this was a bad idea. The roof joists are 2×6. The roof has sofit vents around the entire perimeter of the house, but no gable vents in the center.
My plan is to keep the roof vented and ether install roxul R-15 or dense pack cellulose with a vent baffle in the roof joists and a smart vapor retarder over drywall, keeping a vent gap of 1-2″. I know this is not an ideal solution but I’m trying to increase insulation in the living room until I have funds to replace the roof.
1) Would this situation create more issues with my roof assembly, is there a better alternative?
2) Is it always necessary to have an air sealed baffle in a vented roof?
3) Would making these changes in only one room of the house be a problem? I plan to remodel the other rooms over time. The other areas of the roof have plaster ceilings with about 1 inch of rock wool insulation in the roof joists.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part