Film-coating gives windows temperature control

The research to develop energy efficient windows was undertaken at Oxford University and the University of Pittsburgh and funded as part of the EPSRC Wearable and Flexible Technologies Collaboration. The team’s findings were recently published in ACS Photonics.

“The major innovation is that these windows can change according to seasonal needs,” said Nathan Youngblood, assistant professor of electrical and computer engineering at the University of Pittsburgh and first author. “They absorb near infrared light from the sun in the winter and turn it into heat for the inside of a building. In the summer months, the sun can be reflected instead of absorbed.”

The film is said to be made up of an optical stack of materials less than 300nm thick, with a very thin active layer made of phase change materials that absorb invisible wavelengths of the sun’s light and emit it as heat. That same material can be ‘switched’ so that it turns those wavelengths of light away.