Switchable Windows: Efficiency Factor

May 21, 2004
A/V Interiors
For energy-conscious parents, the message to their children may soon be “turn off the lights and window before you leave the room.” That’s because switchable window glazing — glass whose tint can be manually controlled through the use of electricity — has finally become commercially viable. Electronically switchable windows are now finding their way into general use, everything from privacy screens in office interiors to skylights that darken and lighten automatically.Two different switchable window technologies — electrochromic (EC) and suspended particle device (SPD) — can not only darken and lighten tints at the flick of a switch, they can also control and reduce the amount of solar energy transferred to the interior of a building. As a result, these windows will have a major impact on energy conservation.“Our simulations indicate we can expect around 20 percent to as high as 30 percent reductions in total energy use in commercial buildings through the use of switchable windows,” says Eleanor Lee, research scientist at Lawrence Berkeley National Laboratory (LBNL), Berkeley, Calif. Researchers at LBNL have been putting electrochromic windows through their paces for the past few years to determine exactly what kind of savings can be achieved in office buildings.Using both state and federal funding, Lee and her colleagues are also looking for ways to fine tune the balance between automated control of variable tint windows to maximize energy savings and the need for some form of manual control of the windows by the people who work in these office environments. “The objective of the human factors testing is to determine not only if the people are comfortable in the space with electrochromic windows, but whether they are willing to accept the technology if it is fully automated,” says Lee.“We know that when it comes to windows and offices spaces people know what is best to make them comfortable, so you need to provide some user autonomy — the question is how much.”“Initially, we are not going to see skyscrapers in this glass in the next couple of years,” warns John Van Dine, president and founder of  Sage Electrochromics, which manufactures EC glazing and is a sponsor of LBNL’s research. “There is still too much learning from an engineering and HVAC perspective to accomplish that right now. Engineers and architects simply don’t have the experiences with the dynamic skin of the building.”Instead, Van Dine anticipates use of electrochromic windows to occur strategically over the next few years — in atriums, cafeterias, conference rooms, and executive offices. “This will allow for more learning about the product and once this starts happening we expect a geometric progression of adoption from there,” he says.One purpose of the research being conducted at LBNL for Sage Electrochromics is to establish logarithms that will enable building automation systems (BAS) to operate the windows for optimal energy efficiency. Sage also sells a limited amount of its EC glass to Velux, which is using it in its residential and commercial line of VSE skylights. Currently, the company ramping up its production capabilities to meet what it expects will be strong demand from both the commercial and residential arenas.Of the two competing switchable systems, it appears that SPD glazing, from Research Frontiers, Inc., is the more readily available technology on the market. Research Frontiers has been aggressively licensing its technology to window manufacturers and glazers in the past year. One such licensee is Innovative Glass Corp. of Jericho, N.Y., which sells its SPD glass under the brand name of eGlass.Owner Steve Abadi is no newcomer to the switchable glass industry. He first became interested nearly twenty years ago in using liquid crystal technology to create an electronic window shade. (LC windows do not significantly reduce the amount of light transmission, but only the transparency of the windows.) He reentered the window market last year after tracking the progress Research Frontiers made with their SPD technology and became a licensee in November.For now, Abadi is focusing his efforts on the high-end residential market for his SPD windows. “I know the mentality of the affluent consumer and if I can reach them and interest them in the product, I know they are going to demand it,” he says. Innovative is making some sales in the commercial market, but those installations are primarily inside the office to provide privacy screens for board rooms, executive offices, and a smattering of retail showrooms.“I haven’t reached out to the architectural trade in terms of selling them on energy efficiency,” he adds. “They need to know that there are installations out there and guarantees in place. They don’t like to take a chance without having all the information.”Using electrochromic windows on the skin of buildings will require a new understanding of how windows work. “It’s not just a window anymore. It’s a window with a wire in it and architects need to plan for things like junction boxes to power the windows,” says Tom Mifflin, research and product development manager of Wausau Window and Wall Systems, another manufacturer sponsor of the LBNL research.While the power needed for each window is quite small — from less than 1 volt to 3 volts — a building covered with windows all needing electricity will require significant electrical planning. “It is essential that upfront coordination happen with the architects and the trades that will be installing these windows,” says Mifflin. “To work with Lawrence Berkeley Lab and learn these pre-installation issues allows us to provide that information to our customers and architects to explain exactly what is required for these types of installations.”Information gleaned from LBNL’s work on energy usage from lights, available pass-through lighting (instead of turning the lights on), cooling loads, and the effect of the human factor will be rolled together to create operational guidelines for these next generation windows. Lee expects that the California Energy Commission and the U.S. Department of Energy will create incentive programs to help move the products into the market.“They can design market transformation activities, building demonstrations,” she says, “and they will start to change the building codes and standards — all the structure that is needed to make it easy for architects and engineers to specify these windows.”At market maturity —   which could be as early as seven years from now — Sage has calculated payback times for an entire building fitted with electrochromic windows as being just a couple of years, with actual cost savings the longer the building operates. Mike Kyser, Sage’s vice president of sales and marketing, says, “Savings come from reduced need for some HVAC equipment, shades and blinds, and the operating cost savings from less energy needed for heating and cooling and lighting. There is also reduced maintenance because you are not cycling cooling equipment on and off as frequently.”“This product will be valuable not just in areas where the climate is hot,” adds Sage president Van Dine. “The beauty of the glass is that in the winter in places like Minneapolis you can lighten the tint of the windows to let the heat come in and when it gets hot in the summer you can keep the heat out.”Still in their infancy, EC and SPD technologies carry the hefty price tag you’d expect from new technologies — more than $100 per square foot of window space. But while the products may be expensive today, Lee says she anticipates these kinds of window systems will be affordable in the future.“Our goal (and DOE’s) is to achieve a zero energy commercial building by the year 2025,” she says, “and we are betting on switchable window coatings to get us there.”Chris Anderson ([email protected]) is a freelance writer and editor based in Portland, Maine, who writes about the construction industry.

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