Step 3: Building wall frames
I also framed in two (2) openings for the fans that measured 18 inches by 18 inches.
I also cut a 4 inch by 4 inch post diagonally in half and lengthwise to create a header for the front and back walls that would match the slope of the roof. Regarding the slope of the roof, the VT plans state that for the best solar efficiency, your roof should slope at the same degrees as your degrees of latitude. It would be approximately 39 degrees for us; however, 45 degrees is simpler to build, will work OK, and is what I constructed with.