Blazing the EC Glazing Trail Will the Next Office Development Wave Mainstream Dynamic Electrochromic Glass?
- Mar 01, 2012
Commercial window experts have great expectations for a budding technology known as “dynamic electrochromic glazing.” Considering that so-called “EC”-coated glass allows property operators to optimize solar heat gain for prevailing conditions—without losing daylighting benefits—experts expect the so-far scantly used technology to gain prominence as hard times dissipate and another development wave progresses.
EC’s main attraction is that—properly installed, operated and integrated with a property’s building management system—the technology can be downright Scrooge-like when it comes to energy consumption. Manufacturers and federal agencies are projecting that commercial developers opting for EC installations can reduce cooling-, heating- and lighting-related energy costs by 20 to 40 percent—or maybe more. And EC’s higher first costs are at least partially offset by the corresponding reduction in the sizes of HVAC systems required to meet peak loads—and also by the elimination of shading-system expenditures.
The new-wave technology offers new flexibility. Powered by low-voltage electric wiring connected to metal-oxide layers “sputter-coated” on the exterior panes, EC glass panels can near-instantly adjust from clear to darkly tinted (mostly bluish to date) or any of various intermediate tint levels to suit the situation at hand.
EC shares tintability characteristics with the somewhat less-sophisticated new thermochromic glazing technology that is also utilized more and more these days. However, it offers far more capability for control. Building managers can switch tinting levels with the push of a button or even make automatic adjustments via integration into modern building management systems, thereby providing optimal solar heat gain coefficient and foot-candle light levels dynamically, depending on variables such as daylight hours, sky conditions, sun position—even personnel time schedules. And as EC technology reduces HVAC loads and eliminates any need for exterior shading devices—or even interior blinds—installations will likely pencil out increasingly favorably for developers as costs continue to fall.
Add it all up and integrated systems utilizing EC glazing technology “can provide solar heat gain optimization we don’t realize today,” observed glazing systems veteran Stanley Yee, a building enclosure specialist with consultant The Façade Group. “Ultimately, we’ll have the capability of controlling daylight, glare and heat gain simultaneously.”
In addition to comfortable temperatures, EC glazing embraces the health, productivity and economic benefits of daylighting and pretty much eliminates glare issues—all while maintaining views as panels remain transparent at all tinting levels. Tinted glass also blocks rays that fade colors of and otherwise damage building materials, furnishings, carpets and artwork. In fact, a study by the Lawrence Berkeley National Laboratory indicates occupants prefer the ambiance of spaces with tinted EC windows over regular static glass with shades.
Yet considerable challenges continue to block more widespread introduction. Costs of course are an issue, but the nation’s two manufacturers of EC-coated panels—both of which have new plants underway—expect increasingly competitive pricing ahead. They are also planning to produce panels in sizes meeting most commercial building needs, which has not been the case to date.
Installation of glazing featuring electrically powered tinting is also a bit trickier than is the case with traditional windows. Experts expect this issue to be resolved, but more advancements may be necessary to make EC viable with operable windows, key components of today’s popular passive-ventilation strategies. And with respect to energy retrofits, costs and complications associated with accommodating EC systems’ somewhat heavier weights and (mostly) dual-pane configurations are not yet entirely clear.
Still, the consensus appears to be that as cost differentials narrow and experience improves installation and operating efficiency—and demonstrates savings potential—EC’s multifaceted benefits will ultimately outweigh any competitive disadvantages.
“The potential for electrochromic glazing installations in commercial markets will continue to expand,” predicted longtime building designer Randall Vaughn, director of architecture with Gray Construction. Vaughn led the design and engineering team helping green-building technology giant Siemens erect its new LEED Gold wind turbine facility— featuring an EC-equipped office façade—in Hutchinson, Kan.
The system installed on the office portion’s 4,900-square-foot west-facing curtain wall, allowing for variable tinting in 30 distinct “zones,” is performing as expected about a year into operation. In other words, it is confirming the initial analysis indicating an EC installation would be “the most cost-effective system for the given condition,” Vaughn related.
While integrated with the facility’s BMS, the Hutchinson installation is automatically controlled mostly by manufacturer SAGE Electrochromics’ proprietary automation system, which includes commands based on light sensors, time of day and seasonal sun patterns and angles, Vaughn explained.
“The system allows flexibility in system zones and controlling sunlight in occupied areas,” he added. Not surprisingly, the Gray team is actively assessing prospects for additional installations at client projects.
Ditto for the highly active and sustainability-minded development team at the Hines organization, added vice president of conceptual construction Jerry Lea. “These glazing technologies are improving in performance as they also become more reliable and more affordable,” Lea stressed. “So as they continue to get less expensive over time, they may well become a viable means of dealing with energy in curtain walls.”
Yee concurred. “The technology is there; it’s now a matter of establishing critical mass, of developers and users demonstrating will and desire—and of course the availability of financing,” he observed.
Early indications are that EC is more effective cooling buildings when needed than warming structures on cold days. Thus, it is likely to be more effective in hotter climates, with larger windows and narrower floorplates. Of course, in addition to weather patterns, any particular development’s related energy savings will also depend on window orientation and size, as well as BMS configuration.
But with HVAC and lighting accounting for anywhere from about 40 to 60 percent of energy consumed in a modern office building, the two domestic manufacturers of dynamic EC panels—SAGE and Soladigm—say their products can reduce such expenditures by about 20 percent, in addition to other economic and operational benefits.
McGraw-Hill Construction cites even more ambitious estimates from the federal Department of Energy: reductions in energy expenditures amounting to perhaps 40 percent, along with general-operating cost reductions of 20 percent. And because an EC-equipped development should be able to meet its peak air-conditioning load with a 25 percent smaller cooling plant relative to traditional commercial glazing, the up-front HVAC equipment bill should decline by 30 to 35 percent.
As Yee also emphasized, the elimination of shading installation and maintenance costs should likewise be factored into longer-term life-cycle and shorter-term payback-period economic analyses. He has encountered projections of an EC installation paying for itself through multiple savings mechanisms in as little as a year, but suspects three to five years is probably more realistic even in stronger cases.
Those savings are important to keep in mind, since EC panels are running somewhere in the vicinity of 50 percent beyond standard commercial offerings today. A report by Lux Research specifies current EC pricing at $50 to $80 per square foot, although it projects annual declines of 5 percent (and perhaps as much as 10 percent) in the near future. And SAGE is anticipating it can get its pricing down to the $30 to $50 per-foot range fairly soon.
Frank Burdette, project manager for the Southface regional green building organization’s LEED Platinum Eco Office demonstration and training facility in downtown Atlanta, finds the technology cost effective. “You don’t need to invest in an exterior shading system, and it’s much more effective limiting solar heat gain than interior blinds.”
EC is really the only technology being demonstrated at the Eco Office that cannot yet really be considered “mainstream,” Burdette said. The relatively small and simple installation, at the eastern end of corridors on the project’s first and third floors, is programmed to tint during morning hours and thereby limit solar heat gain.
It is one of Eco Office’s most discussed features, as visitors watch tour guides flip the manual-override tint switch, then return to the spot after seven minutes or so to observe the dramatic difference. “It always draws a lot of interest,” Burdette noted.