German Researchers Create Coating to Self-Darken Windows

October 2021

It’s a novel – and ecological – way to get some relief from hot summer days. Researchers at Fraunhofer Institutes in Würzburg and Dresden have come up with a smart coating for windows to make them darken as they heat up. The results of the Switch2Save project promise considerable savings on air conditioning for buildings with large glass exteriors and those in hot climates.

“The electrochromic coating is applied to a transparent, conductive film which can then be ‘switched on,’” said Marco Schott, Group Manager of Electrochromic Systems at Fraunhofer ISC. “Applying an electrical voltage triggers the transfer of ions and electrons, which darkens the coating and tints the window. On the other hand, thermochromic coating works passively. When a certain ambient temperature is reached, it reflects the heat radiation of sun.”

The new technology is currently being tested at a hospital in Greece and an office building in Sweden. The environmental benefits are potentially very significant. The German Environment Agency estimates that buildings are responsible for around 30 percent of the country’s CO2 emissions and 35 percent of its energy consumption.

© Fraunhofer