Its not just a framing job, like it was on the 1st floor. This is a framing and insulation job at the same time.
Let’s look back at the 2nd floor insulation strategy.
Because the 2nd floor exterior wall consists of two wyth, rather than the three, we have a little more room for insulation. We air sealed the building with two inches of closed cell foam. Following the foam, we planned on two layers of rock wool insulation, one layer behind the framing and the second layer between the studs.
This assembly gets us to a R-value of 40 at almost the same cost of the R-28 insulation assembly from the 1st floor.
Back to the job on hand. I decided that I should try to install the first layer of rock wool together with the framing, to keep things simple. The question was, how?
For once, it turned out to be simpler than expected. We put the framing together as usual and lifted the sections into place, making sure the bottom plate was in its final position. We tilted the top of the framing section into the room. That gave us enough space to start stacking the first layer of rock wool between the framing and the closed cell insulation.
Once all the rock wool was stacked behind the tilted framing section, we pushed it into a vertical position and attached the top plate.
The attic, the space between the ceiling joists and roof joist, was a little more complicated because it is a tight space. But we followed the same principles.
What is left now is to install the second layer of rock wool between the studs.
Once it is all done, this will be a very cozy apartment!