With daylighting more desirable than ever, energy conservation a priority, and privacy never going out of fashion, architects and interior designers are discovering they have a wide range of new options, thanks to rapid advances in glass technology and glazing.
One of the biggest juggling acts for architects is to flood their spaces with natural light without admitting excessive solar heat and ultraviolet (UV) rays that can cause discomfort, fade interior materials, and drive up HVAC-related energy costs. Whether it’s on the exterior or separating conference rooms from hallways, windows that offer the right balance of visible light transmittance, reflectance, solar control, manageability, maintenance - and, of course, cost - can make a world of difference in a structure.
“Far and away, the strongest trend we see is toward the look of clear while maintaining performance in terms of solar heat gain and visible light,” says Mark Fanelli, director of new products for PPG’s Flat Glass Business Unit (www.ppg.com). “There’s a significant desire for that. There are a number of recent examples of sites utilizing clear glass with a high-performance coating. I believe that this move toward a transparent aesthetic was spawned by the green building movement, and it combines the best attributes for architects interested in green as well as daylighting.”
Ideally, a glazing product would transmit 100 percent of the sun’s visible energy and none of its ultraviolet or infrared energy. PPG’s recent introduction of Solarban 60 Starphire architectural glass is an example of manufacturers reaching for that ideal with low-emission (Low-E) glass, blocking more than 60 percent of total solar energy while allowing 70 percent of visible light to pass though. Meanwhile, new manufacturing enhancements have brought down costs, resulting in an extremely clear glass that doesn’t hurt energy performance or the budget. This enables architects to specify it for applications such as vision glass, skylights, entries, and spandrels.
Other manufacturers in the space, such as CP Films’ VISTA Window Films (www.vista-films.com), put heavy R&D into the various window film processes, including laminating, metalizing, vacuum coating, and dyeing, to create ever-improved combinations of solar control and transparency. Products such as VISTA Ambience VE 35 SR CDF have been specified in high-altitude residential applications, for example, where the company claims they block 99.9 percent of UV light and provide a 64-percent reduction in glare. According to VISTA, fully half of home energy bills are the result of heat loss or gain through glass, making solar control films particularly crucial to the ongoing costs and conservation capabilities of homeowners.
While glass with such advanced properties makes a great deal of sense in a wide variety of applications, these products are not necessarily for all tastes.
“If there are options, I don’t like films or anything that changes the color of light that comes through,” says David Ashen, founder of David Ashen Design, a cutting-edge New York City-based architectural firm. “The thing that’s nice about natural light, to me, is it affects the mood of the room. If you play with it or tint it, it tends to have a negative effect. I use treatments that tend to modulate the light: solar shades or vinyl blinds that allow people to see through, or you can open it up for full view without obstruction.”
For architects or clients with similar tastes, or in places where sunlight is an issue only occasionally, the flexibility of transparent window shades can provide the solution. Halcyon Shades (www.halcyonshades.com), for instance, are transparent devices that can be raised or lowered with a cord and roller mechanism but feature solar heat reduction properties similar to glazed windows. Hanita Coatings (www.hanitacoatings.com), likewise, offers a range of reflective two-ply solar shades. When available, solar shade embossing patterns help reduce direct and indirect glare, as well as reduce the direct reflectivity of the shade surface - an aesthetic benefit to both internal and external viewers.
In an increasing number of cases, from residential to retail, clients are seeking an added layer of manageability in their windows. While no longer young enough to be considered revolutionary technology, switchable glass that can have its properties altered with the application of electrical current - including electrochromic (EC), liquid crystal (LC), and suspended particle device (SPD) glass - is certainly still in a state of rapid development. With more players in the space, falling manufacturing costs, growing awareness among architects, and increased customer demand, switchable glass appears to be surging as an architectural component.
According to Greg Sottile, director of market development for Research Frontiers (www.smartglass.com), which produces SPD-Smart technology windows for a wide range of applications, switchable glass is coming on strong for a variety of reasons. “You’ve got a lot of interest in daylighting,” he points out. “There are a limited number of findings that show daylighting in retail environments yields more sales per square foot, and daylighting in office environments is leading to lower absenteeism and higher productivity. From a health perspective, you want to bring the light in, but if you want to control it because if it’s too bright or hot, you’re stuck - then you need shades or blinds, but they’re heavy, collect dust, have moving parts, and take up space. For consumers who want more control over their environment, this is the need that smart glazings will fill: They control light and will do so in any kind of space.”
While manufacturers take various approaches, the functioning of Research Frontiers’ SPD-Smart glass illustrates the working principles of switchable glass in general. By either turning a knob or being triggered by a sensing device like a photocell or thermostat, microscopic particles within the film become aligned when a small electrical current is applied. The greater the current, the more aligned the particles are and therefore the larger amount of light that is transmitted. The film is sealed between two pieces of tempered and laminated glass, then hermetically sealed around all the edges, with all electrical connectors concealed and insulated from the user. Many products in this space are UL-rated.
Depending on the client’s needs, different types of switchable glass offer different types of functionality. “LC glass is mainly used for light diffusion,” says Steve Abadi, chief executive officer of Innovative Glass Corp. (www.innovativeglasscorp.com), a Research Frontiers licensee. “It gives you the ability to have privacy by switching from frosted white to clear, and typical applications are bathroom windows for residences, conference rooms, hospital emergency rooms, theatrical applications, and skylights.”
Likewise, Abadi says, SPD has similar attributes: “In its unpowered state it’s dark, and as you apply electricity it starts getting clearer and clearer. It is infinitely adjustable from a light transmission range of less than 1 percent to as clear as about 70 percent, and can be regulated anywhere in between. Although SPD can go quite dark, however, it doesn’t give you privacy, while LC is either on or off, and gives you privacy.”
Other emerging players in the switchable glass space include the LC film-based PolyvisionT/Privacy Glass from Polyvision (www.polytronix.com), as well as Electric Glass from BEI Automation (www.beionline.com), which offers a variety of material and thickness options, plus some guidelines for architects to keep in mind.
“The maximum size we can make in one piece is 39.5 inches by 10 feet long, although that will change down the road,” notes John Hogg, national sales manager for BEI Automation. “Two other things architects need to consider are they have to run 110 volt current to the windows, and what type of glass they want. There are a lot of options. Most of the time we use a 3/16-inch shatterproof glass.”
Sometimes architectural clients are concerned with blocking out more than just UV rays and big AC bills. Security needs and extreme environmental factors can necessitate explosion-resistant glass to provide a barrier against bomb blasts or bullets - incidents in which 80 percent to 85 percent of injuries or deaths are caused by flying glass - forced entry, seismic events, windstorms, and more.
In such cases, a product such as LLumar Magnum protective films (www.llumar.com), made with DuPont Teijin's Mylar polyester film, is a serious option. Here, the design is intended to provide fragment retention, manufactured using layers of polyester film featuring adhesive on one side and a scratch-resistant coating on the other. Meanwhile, it holds up its end on the thermal front, with high-heat rejection properties that block out 79 percent of solar energy. Available in clear, tinted, or other custom configurations, such films are practically undetectable and can provide peace of mind along with improved views.
No matter what the design or application, glazings continue to undergo rapid development, giving architects unprecedented levels of flexibility for opening up spaces to the rest of the world. Clearly, that’s a very healthy development.