Single pane, double pane, thermo pane, triple pane windows, plain glass, leaded glass, low "e" glass, wired glass, and tempered glass, too. WOW - There's a lot to know!
Some children have been known to shatter a window or two. Tempered glass can prevent this. Fogged thermal pane windows might need to be replaced if their seals are broken. New argon gas filled windows work well to insulate, while low-e coatings reduce the heat transfer for south facing rooms.
There is a lot of information available on the web, but this site seems to be one of the best ones out there. We will be happy to show you the different types of windows and glass as we show you around homes, so be sure to ask us.