2 x 8 Zip R wall
In thinking about building a slightly better than pretty good house, I came across a Build Show video with Matt Risinger and Steve Baczek where Steve was walking thru a house he designed with the following wall assembly:
2. Vertical furring strips
3. Asphalt paper
4. Zip R9
5. 2×8 on 24 inch centers
6. Closed cell spray foam (2 inches or so)
7. Roxul R15 batts
He doesn’t say exactly where other than outside of Boston. Would guess climate zone 5 to 6. The wall he describes doesn’t fit nicely within the 5 Walls that Work, but it seems like a really interesting and very buildable approach to constructing a high performance wall. With the caveat and assumptions that we get the air sealing details nailed, where does this wall fall short if it does at all?
To me it would seem that the first condensing surface for outward vapor drive would be the closed cell spray foam and that would keep the sheathing part of the Zip safe as any moisture that hits the closed cell could dry inward thru the Roxul and then Drywall.
Here is a link to the video for those that aren’t familiar with it or haven’t seen it.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part