Science and Technology

Cool coating for windowpanes

| Updated on September 12, 2021

Windows that darken intelligently to prevent rooms from heating up

Researchers at the Fraunhofer Institute, Germany, have developed an intelligent coating for glass windows that darkens in the sun. This uses electrochromic and thermochromic materials, which react to electricity and heat, respectively. In buildings with large glass façades, the coating prevents rooms from heating up due to solar radiation, thereby reducing the demand for energy-intensive air conditioning.

The building sector is one of the biggest emitters of greenhouse gases. Large glass façades and roofs are particularly problematic, as they heat up in the sun. Air conditioning, increases the carbon footprint of the building.

The Fraunhofer Institute’s transparent coatings add a variable, transparent dark tint to the outside of windows, keeping rooms cool. The electrochromic coating is applied to a transparent conductive film, which can then be “switched on”. Applying an electrical voltage triggers the transfer of ions and electrons, which darkens the coating and tints the window. On the other hand, the thermochromic coating works passively. When an ambient temperature is reached, it reflects the heat radiation of the sun.

With electrochromic elements, sensors can transmit readings such as brightness and temperature to control systems. This sends a voltage pulse to the film, triggering the window to darken. The glass surface gradually darkens with rising temperature or brightness level.

Published on September 12, 2021

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