The technology that’s used in homes has improved immensely over the last several years, leading to appliances and technologies that we would have never imagined possible. Homes are becoming more high-tech and the technology used for windows is no exception. There’s a new type of window with technology known as switchable glazings that’s hit the market and increased in popularity. These windows are considered smart windows and the glass can do some incredible things. The windows detect environmental factors and determine how much heat or light to allow through the window. Here are the four basic types of switchable glazes that can be used in new windows.
A liquid crystal glaze is the first type of window that was available commercially and has been mainly used to enhance privacy. This type of glaze uses two layers of thin film that hold another layer of small liquid crystals. The two layers of film are placed between two layers of heat-treated glass. Both sides of the film are covered with a transductive metal coating that is also transparent. The glass is typically opaque, but when an electrical current is sent through the glaze, the window becomes clear. The window lets in the same amount of heat and light, whether it’s on or off, so it’s main benefit is privacy and preventing people from seeing inside a home or building.
By using a switch, these windows can go from completely clear to fully dark in an instant. Two layers of a traditional glaze are placed in a unit of insulated glass and in between these layers are various layers of electronic conductors, counter-electrodes, and ionic conductors. The windows change color because of low-voltage currents that trigger the ions. Reversing the voltage will cause the windows to revert back to their original color. The windows only use energy when changing color, and only use one to three volts, making them fairly energy efficient.
These smart windows detect changes in light and then tint themselves accordingly. This type of window succeeds at controlling glare, but doesn’t do so well with solar heat gain. The lower sun in the winter causes the windows to darken more than they do in the summer, which is the opposite effect you want to happen if you’re looking to control heat gain. This technology is still being developed, because it’s worked well with smaller pieces of glass, but not for the size of glass that goes into a window.
Gel-based coatings are the best to produce great results in thermochromic windows, which move from clear to diffused to white and reflective according to how much or how little heat occurs. Response temperatures can be adjusted based on where the windows are located. Currently, there are a few products commercially available that utilize thermochromic technologies, mainly because the gel coatings can be used on nearly any window assembly.