I’m in climate zone 5A (Toronto, Canada) and have been weighing the costs/benefits of various assemblies. I was considering 4-6″ of mineral wool on my exterior, then moved on to looking at a perforated EPS (semi-permeable) proprietary product, and am now thinking about cellulose. I’d like my roof and wall assemblies to be similar. My current in->out layers look like:
1. 2×4 chase wall
2. 2×6 structural wall (filled with 3.5″ of mineral wool batts)
3. 1/2″ plywood sheathing
4. Pro Clima AdHero WRB (10-11 perms) as air and water control
5. <thermal control layer>
6. 1/2″ to 3/4″ air gap (venting)
7. 1/2″ OSB+1/8″glued on impermeable cladding.

Bottom of wall skirted 8-10″ with mineral wool regardless as primary gate against pest entry, not to mention bug screen.

As I mentioned, thermal control might have been mineral wool or EPS, but I have been thinking about dense packed cellulose in a modified larsen truss. I would use something like tyvek as air control on top of that to keep the cellulose dry, notwithstanding vapour movement. I would be targeting 40:60 out:in ratio on wall and roof or higher.

On the roof, the assembly would be similar, but with 7″ mineral wool below deck, a larger vent gap and a steel roof.

Some decisions are are set in stone (1 through 4 above), so I’m hoping I can pivot to cellulose.

I’m familiar enough with the pros/cons of mineral wool and eps, that mineral wool is magical, but the economics are confounding. The cost ratios of MW:EPS:Cell are 32:24:10, at least for my area/sources, and at equivalent R-values.

I appreciate any feedback/recommendations on making cellulose work, even if it’s challenging. If it’s practically impossible, I’ll have to accept it, move into a camper van, and drive to nicer climates.