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 has a single awning-style window.  We installed all of these today leaving just the four awning-style windows in the loft to finish.