It wasn't so long ago that most windows held only a single pane of glass. Nowadays, multiple panes are the norm. By way of example, Lincon points out that many of the window styles installed by Sears Home Services are double-paned—in part for structural strength, but even more so for enhanced efficiency. Plus, Lincon says that between the two panes of glass in Sears Weatherbeater windows, there's a sealed unit of argon gas. Colorless, odorless, and non-toxic, the denser-than-air gas provides an added layer of insulation. "Put your hand to an old window in winter, and it's cold to the touch," Lincoln remarks. "New windows keep the cold out and the warmth in—the way it should be."