Continuing Education: Dynamic Glass
Three design teams explore the potential of electrochromic-glazing technology to enhance building-envelope performance and aesthetics.
Designed and built in 2010 and 2011 by architect Dan Rockhill with Studio 804 (a graduate program he directs at the university's school of architecture), the super-insulated, wood-frame building is LEED Platinum and Passive House'Certified. Unique to a passive building is the lack of shading devices on its butt-glazed south-facing curtain wall. To escape the strictures of a typical 'green' building envelope, the architects employed a relatively new glazing made by SageGlass on that elevation'one that uses electrochromic (EC) technology to modify the glass, so it tints dark to block the brutal Midwest sun in summer and remains clear during the winter to capture solar heat on a limestone trombe wall 2 feet behind it.
Electrochromic glazing is gaining traction with an increasing number of architects and sustainability professionals for its ability to manage solar heat gain, visible light transmission (VLT), and glare. One of two architectural dynamic glazing technologies, this 'active' system has been commercially available for just a little more than a decade. It comprises a double- or triple-pane insulated glazing unit (IGU) with an electronically chargeable metal-oxide coating applied to the interior side of its outermost pane. When activated by a low-voltage current, the coating shifts from a clear to a dark state, varying among four VLT levels. Programmed by the manufacturer to tint in response to location and orientation, EC systems include sensors that monitor existing sky conditions and manual overrides for specific needs. (The second dynamic option, thermochromic glazing, uses a film that tints when warmed by the sun. While effective for managing heat gain, it cannot be controlled and does not block glare well in cold weather.)
The ability to simplify the architecture and still satisfy Passive House criteria by tailoring the controls of the CDR's facade is what most appealed to Rockhill and his crew. Meanwhile, in northern California, Sharp Development, working with green engineering consultants Integral Group and RMW Architecture, used the material to transform a 1970s tilt-up structure'located at 435 Indio Way in Sunnyvale'into a net zero energy'cost spec office. To do this, the design team wrapped the 30,000-square-foot, one-story building with a highly insulated envelope that operates in tandem with rooftop photovoltaics, precisely configured motorized skylights that diffuse daylight for maximum spread, and a pattern of EC fenestration from View Dynamic Glass'including operable, motorized windows'on the south, east, and west elevations. This glazing was critical to the scheme, says Integral Group principal John Andary. 'Controlling the glazed areas so no direct sunlight penetrates the building allowed for a small and simple HVAC system'much smaller than we would normally put into a building like this.'
On the recently completed headquarters of the Connor Group, a real-estate investment firm in Dayton, Columbus, Ohio'based Moody Nolan used more than 4,800 square feet of View's EC glass over the atrium and in the west-facing conference room and east-facing curtain wall to reduce heat and glare. The firm is also about to complete a technology center for a Louisiana-based telecommunications company, which features 37,000 square feet of EC glazing.
Manufacturers of the glazing continue to improve its quality and performance'with progressively smarter controls, gradations, and variations of VLT and hue, larger panels (up to 5 feet by 10 feet, to date), and more shapes than rectangles. Ultimately, says Moody Nolan partner Daniel Pickett, quite aside from aesthetics and comfort, 'the secret to this technology is going to be demonstrating the savings on energy costs. Once that can be documented, we will see other projects."