Energy-Efficient Double Pane and Triple Pane Windows When trying to figure out which window glass is best, Mission Glass Company in San Antonio, Texas, suggest looking past obvious fact that a double pane windows has two panes of glass and that triple pane windows has three panes of glass. Double glazing windows are made up of two panes of glass with a spacer. Double pane windows can keep your energy bill low when combined with fiberglass frames. On the other hand, triple pane windows consist of three panes of glass and two spacers. The triple pane windows offer a great difference in performance vs a double pane window. The triple pane windows are much heavier than the double pane windows, but the extra weight does not affect everyday use.