Any experience with BASF HP+ Wall system?
We are building a 2 story 1300s.f. Laneway suite on a small midtown lot in Toronto, Ontario climate zone 6. It will be an all electric, high performance build. l am considering the BASF HP+ XR wall system. The spec is attached. It is 2″ of GPS foam on 2″ horizontal wood girts supported on 2×4 on 16 inch centres with 2×6 top and bottom plates. 3″ of WALLTITE closed cell spray foam encapsulates the girts and partially fills the 5 1/2″ cavity as an air barrier. WRB is either taped / sealant of rigid foam joints or tyvek then furring and rainscreen. It appears to meet my performance requirements and leaves a 2 1/2” service cavity under the drywall, all within a 2×6 wall. Does anyone have any experience or opinions on this wall system?
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I don't have experience with it but I'll tell you what I think. Mostly, I think they are trying to sell their expensive closed-cell foam. I would think you could get the same performance at lower cost and lower carbon footprint by doing something similar but with a cheaper insulation, say dense packed cellulose, in the cavity. (You might need to increase the GPS foam thickness to 2.5" if you use fluffy insulation.)
Apparently they they have some kind of testing to show that they can get away with no sheathing, which is kind of attractive at the moment given how much OSB and plywood cost. You would need to make sure your local building inspector is OK with that system.
Usually for these types of pre-fab walls the big issue is how you'll get them on-site and installed. I looked at pre-fab before and the cost of crane+transport was way more than the cost of framing up the walls on-site. Never mind that extra cost for pre-fab and the engineering.
The wall shown would work quite well, but so would a standard 2x4 wall with batts covered with 2" of rigid polyiso. Same 2x6 equivalent thickness.
The only benefit is that pre-fab can be erected much quicker, so if that is important, it might be worth the extra cost.
They aren't selling you pre-fab wall panels. They are selling you the idea of a site-built wall configuration that uses lots of their materials.
Their instructions for building it are here: https://walltite.basf.ca/pdf/HP+%20Wall%20Systems%20Installation%20Manual_2020.pdf
One thing that looks annoying is that the sheathingless wall is not self-supporting until you foam it, so you need to add bracing, which you later remove.
As pre-fab, it made some sense, site built that is just silly.
SPF is the last thing you design into a new construction project. That is at minimum a $20k line item you are adding to your build for not much benefit.