Open Cell SF in double stud wall? – GreenBuildingAdvisor

Howdy folks, 

My architect and I have designed a variation of the “double stud wall simplified” as detailed on 475 High Performance Building Supplies. https://ca.475.supply/blogs/design-construction-resources/the-double-stud-wall-simplified-low-cost-high-performance

We have a 5” gap between interior and exterior walls, for a total wall thickness of 12” on the main floor and 14” in the basement, and have planned for dense packed cellulose in combination with Pro Clima membranes.  

It is proving slightly challenging locating a dense pack installer in my area. I’m keeping my eye open for a second hand dense packing machine, but if I cant find either I’ll be needing to look at alternatives. Other than using batts, the only other option would be open cell spray foam. I’m aware of the environmental implications and not really looking for that debate at this time.

If one were to use OcSF in this wall assembly, what modifications would be needed? I don’t believe an interior vapour barrier would be needed. There would be a minimum of 8.5” of OcSF, but we could also have the entire depth of the cavity sprayed. The interior stud bay would be treated as a service cavity then filled with batts or OcSF once mechanical/electrical is complete. 

I’m not 100% sure of my climate zone (6 or 7?)but I’m near the north shore of Lake Superior in NW Ontario, about 350 miles N/E of Minneapolis. We have cold dry winters (-30c and beyond occasionally) and mildly warm but fairly dry summers (25-30c).

Thanks for any input!