How can glass be insulated and still let sunlight in and allow us to see out?
Insulated vinyl replacement windows were first comprised of thermal panes, or two or more pieces of glass sealed together to form an airtight center. They stopped most of the heat from escaping in the winter and much of the heat from entering in the summer. Next, thermal window panes were coated with an invisible film that enhanced their insulating properties. They kept even more warm air inside in the winter and more cool air inside in the summer. Most recently, the insulating properties of thermal panes have been further improved by filling the spaces between the layers of glass with special gases.
