Where is my thermal envelope?
Today is a big day in our construction project. We have completed framing the 2×6 external wall on the second floor of our 2-story house, and are building the conditioned space above the garage. Once again, Babyfoot has not used any polyurethane based spray foams to insulate this thermally sensitive area. More importantly, our design maintains a continuous air barrier underneath and around the room above the garage. What this means is the garage is not part of the thermal envelope.
How did we achieve ultra-energy efficiency with an integrated garage?
Firstly, our design does not require any plumbing or ducting to be routed through the unconditioned garage space to service this second floor room. All plumbing and mechanical systems are located in the drop ceiling above the room.
Secondly, we have a continuous vapor barrier underneath the floor of this second story room (see picture below). The in-floor vapor barrier was constructed using 2″ thick SB44 silverboard(R10) product that was subsequently taped at the seams (see picture below)
Then, the 2×6 walls were filled with Roxul R22 batts and a 2×4 load bearing sub-floor was built above the sb44 Silverboard, and subsequently filled with Roxul insulation(R22).
This floor is then covered with plywood and the 6 mil poly that was tied into the Silverboard sub-floor is extended into the 2×4 internal wall, forming a continuous vapor barrier (notice the 6 mil ploly behind the 2×4 studs).
The blue tarp was left on top of the plywood to protect the sub-floor from the elements… The roof will be up shortly!