Hi, everyone. With the following wall system that we’re building (climate zone 7), I’m wondering if we need window bucks and how the exterior insulation should line up with our window openings. 

Our wall system:

1) Drywall
2) Vapour barrier (Intello plus)
3) 2×4 stud wall with rockwool
4) 2×6 stud wall with rockwool
5) 1/2″ plywood sheathing
6) WRB (Solitex mento 1000)
7) 1.5″ of chrome GPS rigid insulation
8) Vertical strapping (1×4, 16″ OC)
9) Horizontal strapping (1×4) (to allow for vertical siding)
10) Siding (TBD)

Our windows will be innie windows, sitting flush with the 2×6 wall. For the rigid insulation, I was planning to overlap the insulation overtop of the window frame (maybe 1/4″) to better insulate the rough opening and the window frame, given this is a weak point for thermal bridging. 

When it comes to strapping, I would then place the rows of strapping up against and around the window opening to provide a base for the siding to attach to. 

Does this make sense? I guess the strapping is acting as the window bucks in this scenario, but not sure if I’m missing anything or might run into issues as I’m actually putting this together. Any advice would be appreciate!