I've detailed curtainwall and I"ve detailed window systems in
commercial applications, hospitals, institutional buildings, etc.
People indicate that curtainwall is an easier material to seal to,
which I don't disagree, but window systems can be effectively sealed
to the air vapour barrier, using foam... I tend to return the membrane
airseal inboard along the rough opening, caulk/seal it to the window
frame, then specify low-expansion foamed insulation applied from the
In fact, one could omit the rod and just caulk the inside joint for
appearance, given the fact that the foam will probably seal the
airseal membrane to the window.