In the quest to make buildings more energy efficient, windows present a particularly difficult problem. The U.S. Department of Energy estimates that heat that either escapes or enters windows accounts for approximately 30 percent of the energy used to heat and cool buildings.
Massachusetts Institute of Technology professor Nicholas Fang is part of a large collaboration that is working together to develop smart adaptive control and monitoring systems for buildings. “Our idea is to adapt new sensors and smart windows in an effort to help achieve energy efficiency and improve thermal comfort for people inside buildings,” Fang says. His contribution is the development of a smart material that can be placed on a window as a film that blocks heat from entering. The film remains transparent when the surface temperature is under 32 degrees Celsius, but turns milky when it exceeds 32 C.
The smart window's milky appearance can block up to 70 percent of solar radiation from passing through the window, translating to a 30 percent reduction in cooling load. Fang's team also hopes to embed windows with sensors that monitor sunlight, luminance, and temperature, as part of what Fang calls “an integral solution to reduce the load on HVAC systems.”