Windows, more formally referred to as glazing or fenestration, affect the daylight that can be effectively used in a building as well as heating and cooling loads. The windows you choose can make a significant difference in your energy consumption—in both new or retrofit situations, they can cut annual energy costs by up to 20 percent in perimeter zones if properly employed.

Cooling represents the major energy load in most large commercial buildings, so glazing that transmits adequate light for daylight activity while minimizing solar heat transmission is usually best. In buildings where heating is the major energy load, glazing should be carefully chosen to minimize heat loss and, in some cases, configured to increase passive solar heat gain while maximizing daylighting.

What Are the Options?
How to Make the Best Choice
What’s on the Horizon?
Who Are the Manufacturers?