Window Installation Now that we have created a pretty airtight structure we can begin poking holes in it. To ensure our next blower door test is as good as the 1st one we have to maintain our air barrier. Step 1 Cut open the window rough openings I was very impressed at how well the inner wall and outer wall rough openings lined up! Step 2 With the Zip board removed, we used 6" Grace Window flashing to extend the Zip System to the inside face of the inner wall. With the air barrier extended into the house we can build the solid window buck. Step 3 We chose to use 1/2" zip board (the cut out section of the window) for the 2 sides and top. We used left over sub floor for the sill. I figured the thicker sill material would be a good idea with a heavy window suspended between the 2 walls. Step 4 Now we need to install our 2" rigid foamboard to insulate the window buck and prevent "short circuiting" around the window frame Step 5 Install beveled rigid foamboard t...