We started installing windows today. We started with the two smallest windows on the north side. First we built the plywood box that spans the inner and outer stud walls (see interior view). Then add a spacer frame at the exterior face that will give us space to line the box with 1″ of rigid foam. Then we tape the entire opening using a rubberized-asphalt tape (Grace Ice and Water Shield) (step 1). We start at the sill, then the jambs and then the header. The tape seals the sheathing to the frame. We are using a drainage plane detail so we staple on furring strips around the rough opening over the tape (step 2). Then insert the window and tape the window flange jambs and header to the sheathing (step 3). The sill flange is not taped to allow drainage.
Later we will shoot low expansion foam into the gap between the window and frame from the inside to air seal the window to the exterior shell.