In years to come, electrochromic (EC) windows, which control the amount of solar heat that passes through window glass, are likely to change the way consumers think about the function of windows.

EC windows allow solar heat–gain through the glass in the winter, reducing the amount of energy needed for home heating. They also significantly limit the amount of solar heat–gain in the summer and still allow visible light to pass through the window, reducing the amount of energy needed for cooling.

In recent years, homes that did not traditionally incorporate air conditioning, mainly located in northern climates, have added air conditioning and increased their energy demand. Utilizing EC windows in these climates may reduce the need for air conditioning completely, while increasing the use of free solar energy for heating. And using EC windows in hot climates reduces demand for cooling energy.

The NAHB Research Center is testing EC glazing in window assemblies at a home in Houston with support from the DOE and in collaboration with the national Partnership for Advancing Technology in Housing, Andersen Windows, and EC glazing manufacturer Sage Electrochromics. The evaluation compares prototypical and control window systems in a production home. The primary goal is to evaluate the home's energy performance as it relates to the cooling system's operation.

It is expected that EC windows will be available commercially in the next few years in the form of specialty windows and skylights. Other types, sizes, and shapes of EC windows will likely reach the market in the next three to five years.

To learn about EC windows, visit, e-mail, or call the ToolBase Hotline at 800-898-2842.

Learn more about markets featured in this article: Houston, TX.