Consider These Window Factors
Special coatings. A variety of special coatings can be applied to the glass pane during manufacturing to further reduce the amount of heat transferred through the glass. Low-emissivity glass (or Low-E glass, in industry jargon) is designed to reflect infrared heat back in the direction it came from. In the summer, it keeps the infrared heat out. In the winter, it keeps the infrared heat in.
Multi-pane glass. Double-pane windows incorporate two parallel sheets of glass with an insulating dead air space between them. Because of the extra pane—and more importantly, the space between the panes—double-pane windows greatly reduce the amount of heat transferred through the window.