Gasochromic glass speaks to what is gasochromic gas and why use gasochromic gas.
It is another developing switchable technology for altering the light transmittance of glass. In this way the transparency of a reactive coating on the number 2 surface of the insulating glass unit is altered by the pumping of gas into or out of the interstitial space of the unit.
These windows produce a similar effect to electrochromic windows, but in order to color the window, diluted hydrogen (below the combustion limit of 3%) is introduced into the cavity in an insulated glass unit. Exposure to oxygen returns the window to its original transparent state. To maintain a particular state, the gap is simply isolated from further changes in gas content.
The optically active component is a porous, columnar film of tungsten oxide, less than 1 micron thick. This eliminates the need for transparent electrodes or an ion-conducting layer. Variations in film thickness and hydrogen concentration can affect the depth and rate of coloration.
Visible transmittance can vary between 0.10–0.59 with a SHGC range of 0.12–0.46. Transmittance levels of less than 0.01 for privacy or glare control are possible. An improved U-value can be obtained with a triple-pane, low-E system (since one gap is used to activate the gasochromic). Switching speeds are 20 seconds to color and less than a minute to bleach.
The gas can be generated at the window wall with an electrolyser and a distribution system integrated into the facade. These windows with an area of 2-by-3.5 feet are now undergoing accelerated durability tests and full-scale field tests and are expected to reach the market in the near future.
The technology of this type of glass is at this time quite expensive and may be justified as it is yet another example of the amazing range of physical properties and variations in appearance with unique characteristics.