The window industry has witnessed revolutionary changes during the past two decades. Advances in physics and engineering sciences have resulted in many improvements in window design, performance, and construction. Emerging window and glazing technology and research offers exciting potential for development of new and innovative windows and glazing products. The following is a selection from some of the examples presented at the window seminar. Glazing A typical double glazed window loses heat by convection, by conduction, and by radiation.
Radiation accounts for two thirds of the heat loss.
The use of thin films or coatings of metals or semiconductor materials can alter the transmittance, reflectivity, and absorptivity of a surface. Films can be designed to either absorb or reflect various ranges of wavelengths to achieve specific design criteria. Residential windows installed in a cold climate, for example, should admit visible light as well as short wave radiation from the sun but reflect long wave radiation from objects inside the house. Low emissivity coatings applied on glass or on an independent film are used for that purpose. In commercial buildings, where cooling loads are most critical, short wave solar radiation should be reflected to the outside in order to minimize solar heat gains.