Wow. Actual window experts. I'm going to ask here next time I'm about to do something creative.
If house is feeling colder is it really because some windows have lost their 30% argon advantage?
Internet search says:
Windows and Doors | Engineering Extension
Single pane is u value of 1
double pane is 0.5
double pane low-e coating is 0.35
double pane argon filled is 0.4-0.3
triple pane low-e is 0.25