What’s the best WRB option when using foam to insulate your structure / sheathing?
I’m most concerned about the critical details around windows. I plan to use OSB or plywood sheathing coated with StoGuard as the building’s air barrier. This will be covered by Tyvek Drainwrap, followed by two layers of taped foam insulation (XPS or Polyiso). Finally, I’ll have an airgap between the foam and siding (i.e. furred fiber cement). What is the safest option for windows: 1) Use Drainwrap as WRB, flash windows to wrap, then use exterior trim? 2) Use foam as WRB, extend window box flush with foam, install and flash flanged windows to foam? 3) Install building paper on top of the foam, flash to this layer? (Note: Picton Brothers used this third option on their LEED house).