House wrap runs over the sheathing and under the siding, and it is installed over window and door openings and cut out afterwards — so openings are not deducted from the area.
It is a drainage plane, not a raincoat
The wrap's job is to give water that gets past the siding a path back out, and to stop air moving through the wall. It is not meant to be the primary waterproof layer.
That means the details matter more than the field. Laps, tape and flashing integration are what make it work.
Window flashing sequence
Cut the wrap at the opening in an I shape, fold the side flaps in, install sill flashing, then the window, then jamb and head flashing, then fold the head flap down over the head flashing and tape it.
Getting this order wrong is the most common wall leak in new construction, and it does not show up until the sheathing is already rotting.
Do not leave it exposed too long
Most wraps are rated for 90 to 120 days of UV exposure. Past that they degrade and tear.
If siding will be delayed past that window, check the manufacturer's exposure limit before assuming it is fine.
Taping and fastening
House wrap performs as a system with its seam tape, and manufacturers specify their own tape for a reason — adhesives and surfaces are matched.
Horizontal seams overlap shingle-fashion, upper sheet over lower, so that water running down the face passes over the joint rather than into it. Vertical seams overlap six inches or more and land on a stud.
Cap fasteners rather than staples, at the pattern the manufacturer publishes. Staples tear out in wind and leave holes in exactly the layer whose job is to be continuous.
Windows are where wraps fail
Almost every house wrap failure is a window opening, not a field seam. The sequence around an opening is specific: sill pan first, then the window, then jamb flashing over the window flange, then head flashing over that, and the wrap lapped over the head flashing from above.
Each layer laps over the one below so water always travels outward and downward. One layer taped in the wrong order creates a funnel into the wall.
Cut the wrap at openings in an I or an inverted Y so there are flaps to fold in and lap, rather than cutting the opening square and losing the material you need.