I do happen to have a copy of the truss plan that was drawn up for my project. These will be placed 24" on center. You'll note that the trusses are designed to overhang the walls of the garage by 21" on either side. This is part of my passive solar plan, along with five 36" x 60" south facing windows. Could be overkill, but assuming 80% of the window size is unobstructed glazing, I'll have 14.4% glazing to square feet floor space for the first floor. The recommended number is around 9%, but I figure that since my siting isn't due south, this should compensate.
