In the Clear: Taking Advantage of Glass’ Two-Way Street
By Aaron Seward
The great pursuit in glass architecture, and thus the technology that feeds it, is and has been for energy efficiency. More specifically, it is the elusive quest to design the most transparent building possible while at the same time mitigating heat gain and glare delivered by the sun. The failure thus far to achieve a balance between fulfilling this architectural ideal and creating an environmentally responsible and comfortable built environment was aptly illustrated by the recent backlash against glass condos. The Wall Street Journal ran an article this August chronicling a spate of horror stories from residents who didn’t anticipate what it means to live in a glass house at the beginning of the new millennium. The harrowing details included faded furniture, the impossibility of watching television during the day, peeping Toms ogling daughters, Windex sizzling to an impossible-to-remove gunk, and cooling systems unable to compensate for the unfettered glory of the sun.
Aside from these issues of individual comfort and livability, it seems clear that, when looking at how we might reduce our overall carbon footprint, glass (our most ubiquitous contemporary building material) is a good place to start. A study issued by the Lawrence Berkeley National Laboratory (LBNL), a member of the national laboratory system supported by the U.S. Department of Energy, estimates that windows are responsible for 2.15 quadrillion BTUs of heating energy consumption and 1.48 quadrillion BTUs of cooling energy consumption within the United States annually, or 30 percent of building electrical loads nationwide. The same study estimates that an overnight replacement of the nation’s window stock with existing high-insulating glass technologies, such as low-emittance coatings and multi-pane units, would result in energy savings of approximately 1.2 quadrillion BTUs, while a similar upgrade to future technologies, currently under research and development at LBNL, could save a potential 3.9 quadrillion BTUs.
Oddly enough, these future technologies seek to improve energy ratings by taking advantage of the very quality that seems to be glass’ greatest weakness: its transmissiveness. “Glass is one of the few building materials out there that allows energy to flow both ways at the same time,” said Chris Barry, technical director at glass manufacturer Pilkington. “In the summer that can be beneficial by allowing heat to escape the interior, while in the winter it lets in the sun’s warmth.”
Ever since the oil embargo of the 1970s, when energy costs went through the roof, the industry has been trying to make glass walls behave more like brick walls in terms of insulation values. This has been successful to the point that today people who have installed low-e solutions in their homes are complaining that when they sit in their breakfast nook in the morning they feel cold. The alternative to this approach is what is commonly known as “smart glass” or “switchable glazing,” in other words, a glass unit whose opacity or reflectiveness can be altered to deflect or transmit more or less of the sun’s energy, thus creating a dynamic barrier that can be optimally tailored to environmental conditions as they change throughout the day or the year.
Smart glass has been developed in a number of varieties, including polymer dispersed liquid crystal, suspended particle, and electrochromic devices. Liquid crystal glass has become popular for privacy screening (it was famously used inRem Koolhaas’Prada stores), but it has no energy-saving benefits. Basically, two layers of glass sandwich transparent electrical conductors enveloping a thin layer of liquid crystal droplets. When in the “off” position, the liquid crystals scatter light, giving the unit a milky white appearance, but when an electrical current is applied the crystals align according to the electric field and assume a transparent state. The change between these two states is instantaneous and there is no middle ground between them.
Suspended particle glass is almost identical in its assembly, except that microscopic rod-like particles, rather than liquid crystals, float in a fluid between the conducting and glass layers. Without an electrical current, the rods fall into random organizations and tend to absorb light, whereas when a current is applied they align to allow light to pass through. Unlike liquid crystal, suspended particle devices can be dimmed to allow more or less light and heat to pass through. Both of these systems require a small but constant electrical current to remain transparent, while the third system, electrochromic, requires a current to affect the change in transparency, but once that change takes place the current is no longer needed. This system is currently the focus of most smart glass research at LBNL. The system works by passing a burst charge through several microscopically thin layers on the glass surface, activating a layer of tungsten oxide and causing it to turn from clear to dark. The reverse change takes place when the charge is passed the opposite way. A mirror system has also been developed that transitions from clear to reflective. Electrochromic systems remain transparent across their switching range—between approximately five and 80 percent transmittance—and can be modulated to any intermediate state.
According to Eleanor Lee, a building technology expert at LBNL, electrochromic glass is on the cusp of being ready for large-scale use, but there are still several impediments. “It’s an emerging technology,” said Lee, “people don’t know about it, it costs more than available systems, and there are many unknowns.” The building industry is notoriously sheepish about using new materials, as the cost of a major failure could be ruinous, but what the technology needs to get off the ground is exactly the type of investment that a large project would provide. Lee pointed out the New York Times Building, which significantly boosted the research and development of external and motorized shading systems. “Manufacturers are willing to do a big project,” she said. “That amount of money would give them the start up cost to bring in the people to engineer the product.”
Another sticking point, of course, lies with the architectural leadership, who will have to decide whether or not they’re willing to allow the external aspect of their buildings to be tossed about willy-nilly by the whimsy of occupants and the demands of the passing sun.
Aaron Seward is an associate editor at AN.
Barkow Leibinger Architects with Werner Sobek
Trumpf, one of the world’s leading manufacturers of machine and laser tools, won’t open its 90,000-square-foot expansion in Ditzingen, Germany until mid-2009, but one can get a sense of what’s to come from the spectacular Gatehouse, which was designed by Barkow Leibinger Architects of Berlin and opened on the Trumpf campus in late 2007.
A honeycombed membrane of stainless steel cantilevers 60 feet over and floats above a 400-square-foot rectangular glass box that houses a reception and waiting area. The roof is a pattern of triangles that compress based on the changing structural forces over its surface. The roof, which was fabricated in-house at Trumpf, is an interesting formal experiment and a celebration of Trumpf’s advanced laser technology, but it is the Miesian glass box beneath that endows the sizeable overhang with its dramatic effect.
With engineering consultant Werner Sobek and manufacturer Glaszentrum Schweikert, Barkow Leibinger developed a 12-inch double non-bearing facade of two layers of low-emission float glass that gives the impression that the planar roof hovers in thin air. However, as Frank Barkow explains, the dynamic roof sits on a core of four columns inside the box while connected to the glass facade by an accordion-shaped rubber gasket that was developed by the team of engineers and architects specifically for this pavilion. Between the two glass surfaces of the facade, the architects stacked Plexiglas tubes of varying diameter, which provide subtle shading to the interiors. The team developed a custom detail of dark Plexiglas structural posts that run vertically between the glass sandwich panels, which are stronger than glass and make the whole facade read as a transparent plane. The interior glass panel is operable to allow for the occasional cleaning of the tubes, which are glued together for easy access. Together, the double facade, the tubes, and the screens lower the cooling costs of the pavilion. It is at night, when the honeycomb roof is lit by LED lights and when the Plexiglas tubes trap the light from the interiors between the layers of glass in an eerie-looking blurry effect, that the Gatehouse appears ready to drift off in a world of its own.
David van der Leer is a frequent contributor to AN.
Courtesy Simone Giostra/Arup/Ruogu
Xicui Entertainment Complex
Simone Giostra & Partners with Arup
The buildings designed for the Beijing Olympics hardly lacked in spectacle, but New York architect Simone Giostra created one that is aimed more toward the gallery crowd than gym-goers. The 24,000-square-foot media wall called Greenpix, which covers the entire facade of the six-story Xicui Entertainment Complex, is an all-glass facade that collects solar energy during the day and gives off tantalizing patterns of vibrant colors at night. Unlike many similar (though smaller) media walls, typically used for display advertising, this one was created to showcase video works. For its opening, Greenpix’s lead curator Luis Gui worked with Shanghai-based curator Defne Ayas, who commissioned pieces by artists Aaaijao and Shi Chieh Huang of China, and Varara Shavrova of Russia.
However inspiring it may be from an aesthetic perspective, it is the system’s sustainability that is of most interest to Giostra, who developed the wall in collaboration with Arup. Together with two German glass manufacturers, Schueco and Sunways, they created a technology to laminate polycrystalline solar cells into glass panels. “It is the most radical example of photovoltaic technology applied to an entire building envelope,” said Giostra. The solar panels have been embedded in the glass panels, some of which are set at an angle, in a pattern of varying density that depends on the nature of the spaces inside and their requirements for daylight. These solar cells provide energy to the roughly 2,300 LED light points, which are intentionally distributed at a lower resolution than generally used for media walls, contributing to the wall’s special abstract quality.
The standard media wall is designed to have an even light intensity throughout the course of a day, but the brightness of Greenpix’s diodes depends on the weather. After a gray day the facade glows subtly at night, whereas a sunny day results in a feast of color. Arup tested over 200 different full-scale prototypes on site in Beijing for more than a year to see what combinations of interlayer, treatments, thickness, solar cells, and textures provided the highest possible performance. The combination they finally installed is projected to maintain 80 percent of its nominal efficiency for the next two decades, during which the wall is expected to become a platform for site specific works made by future generations of video artists. DVDL
1099 New York Avenue
Thomas Phifer and Partners
With its strict height limits and bevy of bureaucratic institutions, the District of Columbia has long favored architectural harmony and conformity over innovative design. How refreshing, then, to see a commonplace glass-box office building raise the bar for design in the Capital without disrupting the city’s intended uniformity.
Designed by New York-based Thomas Phifer and Partners, 1099 New York Avenue is an eleven-story, 173,000-square-foot office building, developed by Tishman Speyer, with a crystalline facade that expresses its materiality and, thanks to meticulous detailing, offers what Phifer calls a subtle “sense of surprise.” “Jerry Speyer wanted a special building with a unique skin,” said Phifer, “and he wanted to do it in D.C.” On first glance 1099 might look like a particularly well wrought version of the ultra-glassy office building— at times perfectly transparent, at others so reflective as to nearly disappear—such as SOM’s World Trade Center Seven. As you get closer, however, you see that rather than striving for a pure planar surface, Phifer has created something, literally, more multifaceted.
Rather than using a curtain wall system, Phifer opted for a custom window wall over the building’s thin concrete frame (Washington’s height limits make ultra thin floor plates a must). Each pane of glass is tilted six inches in both plan and section, giving the building a sense of depth and shimmer. “We wanted it to be a detail, rather than a gesture,” Pfifer said. “If it had been a big gesture, that would give away the sense of surprise.” A cast stainless steel clip, visible from below, supports the pane. “The clip expresses the weight of the panes.” The five-inch deep by eight-inch long clips also add to the texture of the facades.
The large twelve-and-a-half-feet long by five-and-a-half-feet wide low-emission Viracon panes function like shingles, allowing water to run down and drip off the facades during storms. At ground level, an installation by artist Matthew Ritchie helps enliven the streetscape. The building, which follows the contour of the lot where the Washington grid is bisected by a diagonal avenue, responds to its site, respecting its context while showing that even a small speculative office building, with the right attention to detailing, can reflect higher ambitions.
Alan G. Brake is an associate editor at AN.
M. Moulinet/Polkop/Courtesy Rolinet & Associes
Chapelle des Diaconesses
Rolinet & Associés
In Versailles, in a park dotted with trees, sits the Chapelle des Diaconesses, a cocoon of superimposed pine wood strips inside a triangular glass structure. The small chapel, which opened to the public in 2007, replaced a large cloth tent that the Protestant Community of the Deaconesses used over a period of 20 years for its largest ceremonies. French architect Marc Rolinet’s modern interpretation of religious architecture subtly refers to this former place of worship. The sisters of the parish requested a chapel that would be firmly rooted in the 21st century, and that “offers modern people an interior that combines beauty, intimacy, and celebration, and that invites them to reflect and find peace.”
Rolinet set out to design a lightweight glass structure that follows the hilly topography of the site and provides an arcade between the wood and glass that is now used for quiet reflection. The envelope, made out of laminated safety glass with a structural interlayer by DuPont and manufactured by Saint-Gobain, protects the wooden chapel from the weather and forms an optimal acoustic barrier to the railroad station close by. Stronger than conventional laminating materials, the interlayers help create safety glass that protects against bigger storms, larger impacts, and more powerful blasts. The layers become an engineered component within the glass, holding more weight, so the glass can serve as a more active structural element in the building envelope. And they do all this while increasing framing system design freedom and improving long-term weather resistance. Marc Rolinet stated, “The structural calculations performed by DuPont and Saint-Gobain Glass enabled us to reduce the glass thickness, increase the pitch, and lighten the supporting structure.” Without the structural interlayer, the glass would have been thicker—and therefore more expensive. It also allowed for a direct integration of the fixing devices into the laminated inner glass layers. The structure spans a large distance, and allows for a minimal number of steel girders. But in the end it was the mirror-like effect that convinced Rolinet to use this material instead of conventional laminated glass—an effect that now at certain points of the day allows for a spectacular reflection of the charming park surrounding the chapel. DVDL
LOFTS @ 655 6th
Lofts @ 655 6th, a seven-story, mixed-use project that opened last December on the edge of San Diego’s East Village and Gaslamp districts, uses an innovative glass system to distinguish what is a fairly simple structure from the city’s many other new residential buildings.
The project is one of the few new rental properties in a city awash in high-end condos. In order to save money, maximize space, and create a more authentic loft-like ambience than the traditional configurations that are dressed up to look like lofts, and which are so common today in San Diego, local firm Public built a huge concrete box at the core of the 106-unit building. The 100,000-square-foot structure then steps down to the east to address the neighborhood.
The infill glazing system cladding the core is made up of a varied pattern of small and large glazed squares. All are very transparent, but highly energy-efficient, with a U-value of .41. To further animate the facade, Public hung an irregularly spaced clear tempered glass screen system over the project’s west-facing balconies. The screen is fitted with a perforated vinyl film—similar to the films used to create many billboards—that displays a sepia-toned photo-abstraction of live oak trees, created by photographer Philipp Scholz Rittermann. Not only does the screen add complexity to the building, but its shading helped the building pass its state-mandated requirements for solar gain.
When the film needs to be replaced in about five years, the firm hopes the developer will hold a call for entries to find a new artist, thus ensuring a new look for the building. “Our only agreement with the city is that the new image not be distasteful or commercial,” said firm principal James Gates. The building has been a hit, and is fully leased, despite being completed just prior to the recent economic doldrums. “We’re very proud of what we were able to get for the money,” said Gates.
Sam Lubell is AN’s California editor.