We are using all fiberglass Integrity windows from Marvin. They are fitted with double paned, argon filled, tempered glass with a U-factor of 0.29 and a solar heat gain coefficient of 0.29. The first floor has one large picture window and two double casement windows in the living room. The kitchen has a triple casement window and the bathroom a single awning style window. We installed all of these today leaving just the four awning style windows in the loft to finish.