Dynamic windows that can change transparency to manage solar heat gain, glare, and daylighting are building buzz in the green building world. Operating buildings — cooling, heating, lighting — accounts for about 36 percent of our overall energy consumption, according to the EPA, which is why efficiency retrofits and improving building codes have been a big focus of late. Most energy lost, or wasted, drifts through the building “envelope,” its outer edges. And of course, no surface is more leaky than windows.
But dynamic windows go far beyond the abilities of double- or even triple-paned windows to retain energy. John Van Dine is a chemical engineer who founded Sage Electrochromics 20 years ago. His dynamic windows offer value in a variety of ways, he said. They eliminate the need for window shades and reduce the amount of air conditioning equipment needed. They provide energy savings by reducing cooling loads by 20 percent and artificial lighting costs by 60 percent. And more nebulously, but perhaps most important, they enhance “the human experience in the built environment,” he said. “They block heat or let it in, while preserving the views and the connection to the outdoors, which are the reasons why we put glass in the envelope of a building.”
Indeed, studies have shown that human productivity increases with good “daylighting,” the practice of allowing natural light into a building.
This technology has been in development since the 1960s and is only just now reaching viability for manufacturing, said Murray McCutcheon, an analyst at Lux Research who just wrote a report on dynamic windows and advanced insulation.
Market forces are also encouraging the emergence of dynamic windows at this time. Both building owners and governments have been turning their attention to energy efficiency in the last few years. In particular, the European Union’s aggressive standards have pulled the market. “Windows are one of the major pain points in terms of the energy performance of a building,” said McCutcheon.
Interestingly, while the bottom fell out of the construction industry in 2008 and has yet to recover, “the green building sector has bucked trend and seen some growth,” said McCutcheon. Turner Construction, the largest commercial builder in the United States, attributes more than 50 percent of its 2010 revenue — more than $4 billion — to green building, according to the report.
In the dynamic window space there are two main technologies that improve a building’s thermal envelope by blocking solar heat gain. The first is called thermochromic, a passively responsive technology. It’s optical properties change in response to heat. While it appears to darken in the sun like Transitions eyeglasses, the trigger is heat — not UV exposure. Pleotint out of West Olive, Mich., is the leading company in this sphere.
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