Glass is a very common material in building construction that combines more than a few advantages, such as transparency, natural day-light, blending of exteriors with interiors and acoustic control. In order to achieve better energy performance of buildings, several types of glass are used, low –emissivity glass and glazed glass are the most common, but new technology has been under development for the past few years.
Smart glass, also referred to as switchable, dimmable, or dynamic glass or glazing, varies the light transmittance and thermal properties of windows across a spectrum. As opposed to static high specification glass, which is designed to improve the thermal and daylight performance of buildings but is restricted to set parameters, the properties of smart glass can be varied depending on changing ambient conditions through programming, automation or user controlled to suit needs of occupants. Projections of building performance show significant gains from the use of smart glass, as do other important metrics that are harder to quantify, such as occupant comfort and satisfaction.
The main smart glass technologies available for exterior/façade applications in buildings are:
– Electro-chromic: Change light transmission properties in response to voltage and thus allow control over the amount of light and heat passing through.
– Thermo-chromic: Heat causes thermo-chromic windows to alter their properties. In response to changes in the ambient temperature, a clear thermo-chromic glazing becomes diffused.
– Suspended Particles: A thin film laminate of rod-like particles suspended in a fluid is placed between two glass, or plastic layers, or attached to one layer. When no voltage is applied, the suspended particles are arranged in random orientations and tend to absorb light, so that the glass panel looks dark. When voltage is applied, the suspended particles align and let light pass.
Others glass technologies are still in development stage, like photo-chromic (response to light), micro-binds, and nano crystal.
Finally, despite some problems, smart glass hold the promise of reducing energy demand and cutting air conditioning and heating loads in the future. They offer the next major step in windows that are increasingly sophisticated and energy efficient.