Switchable glazings can help reduce energy usage. Switchable glazings can lower energy costs for cooling a home by reducing direct solar gains, especially in the summer. They can block UV rays and radiant heat (particularly useful for skylights) and lower cooling loads. In cooler northern climates, electrochromic windows can effectively eliminate the need for mechanical air cooling systems altogether.
By decreasing the solar heat gains, electrochromic windows can also help eliminate the need for window coverings such as shades or blinds. That means that homeowners can not only enjoy their surroundings more (keeping a room comfortable, and not too hot), but they can also enjoy their views during the day.
Switchable glazings can also protect a home's interiors from damaging UV rays, so that carpets, furniture, and artwork don't experience fading from the sun. Electrochromic windows also offer more control than windows that are photochromic or thermochromic (these are windows that turn opaque when exposed to light or warm temperatures).
While many might think that the electricity required to operate the switchable glazings is a negative attribute, manufacturers and supporters point out that the energy required to run the windows is minimal. Low-voltage products use less power than line voltage products. Plus, they use virtually no energy to maintain a clear state. Moreover, the energy that is saved by reducing cooling needs and energy expenditures far outweighs the energy use by electrochromic windows.
Solar powered windows go a step further, requiring no purchased electricity to operate the windows whatsoever. In either case, electrochromic windows do not make any other energy demands during their lifetimes – just what's necessary to make the switchable glazings functional.
What are the downsides to switchable glazings and electrochromic windows?
Electrochromic windows can reduce energy usage and sun damage, but they are complex windows that aren't exactly a piece of cake to install. Electrochromic windows that utilize electricity require a non-standard electrical hookup and unconventional wiring (including a switch). That means that homeowners may have to hire an electrician as well as a window installer, or a general contractor or other tradesman who can handle all facets of installation.
Switchable glazings are commercially available, but inconsistently. Few can be found at major retailers such as home improvement stores. Some are for residential use only, some are only available through the manufacturer or select vendors, and so on.
Probably the biggest disadvantage of all is the cost. Electrochromic windows cost significantly more than a standard window, as much as 2 to 3 times more. Liquid crystal glazing can add as much as $90 per square foot to the glazing! As with most 'new' technologies, the price point for these high-tech windows is expected to drop to more reasonable levels as supply and demand increase, technology improves, and manufacturing becomes less involved.
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