I live in Southern California and have an attached den with "mylar" windows. I would like to replace these windows with double pane vinyl windows. One side is abt. 21 ft., the other side is abt. 13 ft. The opened window space is abt. 4'6" above a 30" wall. To do a go job, I think I might need to build a frame, place it between the wall and the roof, in order to purchase presized windows to install. What do you think?
That is one option, another would be to use horizontal sliding windows. With sliders, you could use a wider window and only need to add some vertical supports. With the sliders you'll have more glass space for a less obstructed view. If you dont need them all to be able to open, you could also go with a combination of picture windows and sliders, double hung, or even casements.