When using WINDOW 5 software to calculate the overall U-value of a window assembly, including the frame, I have a big question regarding the number of calculations needed. Suppose that for the building I am working there is only one type of window but the dimensions vary, there are five different sizes of windows, all with the same frame. Do I have to calculate the overall U-value for each window size? Or do I use a standard size?

Any suggestions greatly appreciated.