General Construction & Buildings

Basic development of gas-chromatic window and façade elements for intelligent control of light and energy transmission

The project involves studies on the construction and optimisation of catalytic switchable insulated glass units. The fundamental research focused on a technology based on gas-chromatic layers, which has a controllable light and energy transmission capability and is an effective solution for use in window and façade systems.


By transmitting radiation, glass façades can contribute to significantly reducing heating costs in the winter months. However, this requires good insulating properties. In the summer months, this effect can lead to overheating, making it necessary to cool the interior space. Thus, constructions both with and without glass façades require energy-intensive measures (heating / cooling). Glass façades generally improve the mood of the building's users and lead to further energy savings by reducing the need for artificial lighting. On the other hand, sunlight can cause glare in the workplace.

One method of overcoming the impediments to large-scale use of glass as an energy efficient façade material is to develop optically active layers. These can be used to intelligently regulate the radiation and heat flows.

Gas-chromatic layers have particularly promising prospects. In this type of glazing, the optically switchable layer is made of tungsten oxide (WO3). Feeding H2 into the cavity between the panes shades them blue. You can still see through but transmission is considerably reduced. Overflowing the active layer with O2 achromatises the glass.

The Fraunhofer Institute for Solar Energy Systems (ISE) had central responsibility for fundamental studies into the shading behaviour of the gas chromatic WO3 layers and into alternative layer constructions and colour-neutral mixed W-Mo oxide layers. Outlining details of a gas supply and generation system was another key area.

More Project Information

Project number: 0327233B

Project period: 1999 - 2001

Project region: Germany (Bavaria)

Project contact:

Herr Dipl.-Ing. (FH) Graf

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Source: German National Library of Science and Technology Hannover (TIB)