Garage Attic gets a Thick Winter Coat.
I mentioned in a previous post that my garage will be a workshop. I want it to be fairly energy efficient so I opted to add 3" of exterior foam on the outside of the building to prevent thermal bridging. I also want it to be as air tight as possible...which is probably not that possible with a leaky garage door but we'll see. A typical wall section is composed of 3" EPS, OSB, 2x6 stud wall, then drywall. The exterior OSB joins were caulked with acoustical sealant and further sealed with 3M 8067 tape. The air sealing details in the plans were fairly easy to follow but some thought had to go into transitioning the air barrier from the exterior to the interior. The air barrier upstairs is composed of OSB attached to the underside of the trusses. So at the second floor level upstairs, the air barrier transitions from the OSB on the exterior of the 2x6 wall to the interior underside of the OSB attached to the trusses. Once the gable ends were framed and sheathed, a strip of 15 mil vapor barrier was draped from inside to outside all the way along the top of the gable walls and on the second floor deck to the outside OSB. At this point, trusses were added and the construction continued. At the outside, the vapor barrier was lifted and a bead of acoustical sealant ran along its length sticking it to the exterior OSB. the vapor barrier was also taped to the osb using 3m 8067. Photo 1-1 through 1-3 illustrates the vapor barrier hanging out over the gable top plate and after taping to the exterior OSB (Photo 1-3). The same detail exisited at the 2nd floor deck.
A few hours later the guys had finished filling most of the truss bays (Photo 2-10) and were up to the flat part of the ceiling. Based on the depth of the trusses, the R value is about 60. They will be back next week to complete the job. In the meantime we are going to attach OSB under the trusses where the insulating has been completed. We're one step closer to a finished attic in the garage!
Photo 1-2. Blue vapor barrier can be seen at the top of the garage gable wall between the top wall plate and the truss.
Photo 2-3 ProPink fabric installed under the trusses.
Photo 2-4 ProPink fabric installed under the trusses. Notice the blue vapour barrier. It will be tape sealed to the bottom of the OSB.
Photo 2-10 Almost complete!