Some Window Factors to Consider
Double-pane glass. Double-pane windows are superior to single-pane windows. 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. Additionally, to make double-pane windows even more efficient, the space between the panes is often sealed and filled with an inert gas, such as argon or krypton.
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.
Double-hung windows. Double-hung windows are designed to tilt in to allow easy cleaning from inside the house. This feature is especially nice if a ladder is needed to clean the windows from the outside. Double-hung windows also give the ability to vent from the top as well as the bottom of the window, allowing increased airflow.