Smart Glass Appeals to Green Community
October 15, 2007
FEATURE ARTICLE | Energy Efficiency, Segments
The architectural community is increasingly committed to the sustainable design goals of lower energy consumption and greater levels of building occupants’ well-being and productivity. With the emergence of the green building movement, the window, door and glass industries can expect to see increased demands for higher performing products, including, notably, smart glass. The U.S. Green Building Council’s Leadership in Energy and Environmental Design rating system assesses buildings in terms of their sustainability and performance, and accredits individuals involved in the design and operation of these buildings. In February 2007, my company conducted a first-ever study of LEED accredited professionals on the subject of smart glass, also commonly referred to as dynamic glazing. The results from more than 450 professionals are in, and they point to a future where smart glass plays a significant role in the architectural environment. What follows are some of the study’s key findings.
More than 80 percent of those surveyed said they are aware of smart glass, but just 2 percent report they have specified smart glass for a residential project. This relationship—high awareness, low specification—is consistent with the pattern observed for many other emerging product categories and is due likely to the relatively recent commencement of production of smart glass for architectural applications. What is most telling, though, is how the accredited professionals feel about the future. Usage levels seem poised for a marked upturn, with almost 93 percent of respondents saying they are likely to recommend smart glass for a project if it is priced reasonably and meets specifications (Fig. 1).
DYNAMIC GLAZING TECHNOLOGIES
Smart glass represents a category of glazing materials that visibly change their properties in response to a stimulus. In doing so, smart glazings in windows, doors, skylights and partitions offer varying levels of dynamic control of light, glare and heat. Passive smart glass operates with no electrical interface and is typically found in small-format applications. Self-dimming eyewear that reacts to the presence of ultraviolet light is an example. The most exciting development in the architectural arena is active smart glass products, including those using liquid crystal, suspended particle device or electrochromic technology. Active smart glass requires an electrical stimulus to change its light-control properties, and power consumption levels are very low. Smart glass using suspended particle technology, for example, uses approximately 0.06 watts of power per square foot.
The operating performance of active smart glass depends on the type being considered. Switching speed and the consistency of a tint change are among the most important attributes to potential users of smart glass technologies. Liquid crystal smart glass changes its properties the most quickly of all—from translucent to transparent in milliseconds—and tint changes occur consistently regardless of panel size. Liquid crystal smart glass does not offer a shading benefit, but the view through the glass is blocked when in its translucent state. As such, this product is primarily used for interior needs (e.g., bathrooms) where privacy is required.
Smart glass using SPD technology takes several seconds to change from dark to clear, and tint changes are consistent regardless of panel size. The switching speed of electrochromic glass is slowest overall and varies depending upon the size of the panel (larger panels typically take many minutes to switch). The consistency of tint changes also varies, with larger panels sometimes exhibiting tint changes that begin at the glazing’s outer edges and then move inward (known as the “iris effect”).
Both SPD and electrochromic glass technologies block light and provide shading, making them applicable for exterior windows in addition to interior privacy applications. These smart glass products are particularly well suited for settings where sunlight intensity is strong and view preservation is desired.
Strong interest in smart glass is driven by a belief that green building is here to stay. The LEED professionals surveyed reported that 25 percent of the residential projects they worked on in the past year involved sustainable design. The leading factors driving interest in sustainable design are the potential for greater energy savings (cited by 61 percent of those surveyed), client demand for sustainable solutions (48 percent), the need for lower lifetime operating costs of buildings (35 percent) and advances in sustainable materials (20 percent). More than 98 percent of those surveyed expect the proportion of their projects that involve sustainable design to increase over the next five years.
When evaluating residential glazing, the most important items to this group are energy efficiency, daylighting and aesthetics. Also of note, most (90 percent) of those surveyed said that demand for architectural glazing is on the rise and 97 percent believe that glazing plays an important role in sustainable design.
The recent survey found there were a number of issues related to smart glass that were important to LEED professionals. With their interests in sustainability, it is not surprising that chief among these is energy efficiency. Others include durability, integration with other coatings such as low-E, glare reduction, consistent-looking tint changes, light-control that is tunable to any point between dark and clear states and UV light blockage. Survey respondents were asked to comment on the maximum price per square foot that their clients would be willing to pay for smart glass. While the median maximum price expressed for residential projects was $50 per square foot, 15 percent said their clients would pay $75 per square foot or more.
The architectural professionals surveyed are very committed to the green building movement and eager to apply new technologies to meet sustainability goals. This is a welcome perspective. As recently as 2006, the U. S. Department of Energy reported that buildings’ share of total energy consumed in the country reached nearly 40 percent, a level that extends an upward trend over a period of more than three decades. Smart glass will be an increasingly important arrow in the quiver of green building technologies.
High-performing smart glass products provide unprecedented levels of advanced light-control while also making instant and dramatic design statements. Sleek and innovative, smart glass is tremendously empowering. Just as significant are its array of functional benefits (tunable shading, privacy, glare reduction and remarkable energy efficiency) that support the sustainable design goals of resource conservation and the well-being of building occupants.
Gregory M. Sottile, Ph.D., is director of market development with Research Frontiers Inc. Based in Woodbury, N.Y., the company develops and licenses suspended particle device (SPD) technology used in VaryFast SPD-Smart controllable glass and plastic products. He can be reached at 516/364-1902 or via e-mail at email@example.com.