What to specifically look for in windows based off of geographical areas and climate zones
For all geographic locations:
- Air tightness is important
- Performance grade is important
Northern - Look for a better U-value and insulating value of the window. Triple pane may be a worthwhile consideration to draw the U-value down.
North-Central - Depending on your situation, a good quality double pane glass with a respectable U-value is probably your best investment. Triple pane tends to be an overkill for this geographical climate and adds tint, darkening the view.
South-Central - In this climate, nothing more than double pane would be necessary. A lower solar heat gain rating will begin to be important here to allow less heat in the windows and maintain cold air in the house.
Southern - The solar heat gain rating is going to be essential for this region.