Gold has been used as a thin coating in building glazing to reflect heat radiation, keeping buildings cool in summer and warmer in winter.

Ordinary window glass is almost completely transparent to solar radiation (from the ultra violet to the infrared wavelengths). Thus large glazing areas of many buildings can cause over heating of interior rooms and offices and increased loading on air conditioning installations. The design of glazing to reduce this affect has sometimes used thin gold coatings on the glass, because vacuum deposited films of gold have excellent infrared shielding capability.

In making these materials, it is obviously important that the amount of visible light transmitted by the glass is acceptable and this can be controlled by the thickness of the gold film and the glass itself. Double glazing, with gold coatings, is also effective in reducing heat loss to the outside of buildings during winter.

The use of gold in architectural glazing is illustrated by the Royal Bank Plaza building in Toronto. The building has 14,000 windows all coated with pure gold (70,000g in total). The gold reduces heating and ventilation costs inside the building, thereby making it cost effective. Eureka Tower, the second tallest residential building in the world, has 24 carat gold plated glass windows on the top 8 floors of the building, and was officially opened in October 2006.

For more information on the science and technology of this application download this paper from the archives of the journal Gold Bulletin. Manufacturing gold-coated glass is rather an expensive process (due to the use of vacuum technology rather than precious metal cost) and so research is currently underway to develop new techniques to make these materials. They may involve the use of gold nanoparticulate coatings to accurately ‘tune’ the reflective capability of the glazing. An added advantage of this emerging technology is that a more appealing range of glazing colours can be obtained Read more.