In the center of a once war-torn town, the Jerde Partnership has designed a sparkling new mixed-used project with a retail component that incorporates the most modern — and unique — use of glass products and technology to create an open mixed-use complex that lets the sun shine in.

An undulating canopy covers the equivalent of 110 football fields and emulates the copses of trees in the historic urban parks that ring the city. The canopy protects the plaza underneath from the elements yet at the same time creates the feel of a completely open urban shopping center. And with the addition of heating and cooling systems — often elements of the glass itself — it makes a cozy retreat in brutal winters.

The $500.4 million project isn't located in a grand capital of the world.

It's in Warsaw, Poland.

Zlote Tarasy, which translates to Golden Terraces, is being developed by ING Real Estate and Dutch investor Rodamco in a city that still bears scars from World War II bombing raids.

It underscores how architects consider Europe to be the proving ground for advanced glass building applications. One reason is that developers abroad are often less conservative when it comes to design and in spending more up front for perceived long-term gains. Also, the Americans with Disabilities Act in this country has imposed restrictions for width, strength and access to buildings that create design constraints for U.S. buildings, says a spokeswoman for Callison Architecture in Seattle, Wash.

Still, more energy-efficient glass technology, new “green building” mandates popping up across the country and a renewed appreciation of style are providing U.S. architects new opportunities to make glass more important and a more widely used element in retail and mixed-use centers.

Glass enables architects to create unusual spaces; its transparency, reflection and smoothness lets in natural light and does away with concrete mazes. But the experimentation going on today is a new trend, one Boulder, Colo. — based Communication Arts cochairman Richard Foy calls: “the transparency of architecture.”

“The new world of design is being driven by erasing the boundaries between the interior and the exterior of buildings,” Foy says. “Developers increasingly realize the public realm (streets, plazas, open space) is at least as important — and maybe more important — than the architecture of a project.”

Now, glass is being used in much bigger and, many would say, better applications, for everything from energy-efficient external building shells to curved, elegant canopies. Examples range from the giant one at Zlote Tarasy as well as a leafy covering for smaller outdoor passageways employed by Perkowitz+Ruth Architects at Bridgeport Village in Oregon.

In another example, the 88-story Petronas Towers in Kuala Lumpur, Malayasia, designed by New Haven, Conn. — based Pelli Clark Pelli, features at its base Suria, a six-story shopping center with a vast glass dome.

Foy notes that CommArts' contribution has been to push for taller glass storefronts making its designs 16 feet high, compared to the typical 10 to 12 foot heights found in most enclosed malls. “It's so much more inviting,” he says.

George Marshall, associate at Perkowitz+Ruth Architects in Long Beach, Calif., echoes that thought: “Glass allows shoppers to clearly view the products and the see-through walls allow those outside to witness the human energy inside.”

Window on windows

Glass windows, to put it mildly, have been around for a while.

Archaeologists date the first use of glass to 100 AD when Romans installed rudimentary, opaque windows in buildings. By 1902, Tennessee inventor Irving Colburn was churning out sheet glass on a new production machine he invented. And in 1922, Bauhaus director Ludwig Mies van der Rohe designed what is considered the first glass skyscraper, though it wasn't built until the 1950s when a twin pair of his cubist glass towers went up across from Lake Michigan in Chicago.

Through the ages, however, one major problem has persisted: “The weak point in the envelope in buildings as far as temperature transference, has always been windows,” says Tom Dietsche, a director of the Leadership in Energy and Environmental Designs (LEED) program at the U.S. Green Building Council in Washington, D.C., which encourages environmentally friendly construction.

At least 25 percent of building heat loss comes through the windows, says Vivian Loftness, Carnegie Mellon professor, of architecture, LEED-accredited professional, and research faculty member in the Center for Building Performance and Diagnostics. “We could cut that in half or even by four times, by using new window technology given the advances in the last 20 years, which would save an enormous amount of energy in the U.S.

“All of a sudden, we're seeing leaps in development of improved glass characteristic and it's only going to get more inventive,” she says.

With this in mind, some states are legislating energy cutbacks in buildings. California's Title 24, for example, calls for increased fuel efficiency in residences and commercial buildings. The latest amendment to that law, Cool Roof Coatings Performance Requirements, took effect September 11, 2006. And in the state of Washington, the Watson Program is imposing ever more strict rules on energy efficiency.

In recent years, glass manufacturers, including PPG Industries, Pilkington and others — working with architects and developers — have been creating new products that block the heat and retain the cool. PPG Industries, for example, this year introduced Solar Ban 70XL, which increases visible light transmission, cutting back on the need for expensive traditional lighting — while blocking more heat from penetrating the glass through the use of a microscopic film coating. The result: less need for air conditioning and therefore less electricity.

Meanwhile, canopies, including the one designed by the Jerde Partnership, use glass panels up to one-half inch thick in skylight areas. A piece of vinyl inserted between two panes serves as insulation in addition to helping keep the glass from shattering and falling if it becomes broken.

Other new glass technologies include, fireproof glass that shatters at higher temperatures than conventional glass, increasingly sophisticated use of small photovoltaic cells in window panes to generate solar power and, if you will, multiple layer glass sandwiches that can incorporate laminates. Some systems add argon gas between the panes. (Argon gas fills reduce heat loss by slowing down the convection of heat from inside to outside.)

None of this comes cheap.

The argon-filled panes alone cost five times as much as regular glass, which is part of why most usages of the technology to date have been in high-end residential projects rather than commercial buildings.

And David Rogers, Jerde senior vice president estimates the price tag of the dramatic glass at Zlote Tarasy was double or even three times a prosaic flat-roofed mall.

But, Rogers says a long-term outlook ultimately amortizes the added expense — and assures buildings comply with the increasingly stringent state and federal regulations being enacted.

“Look at the cost of a component of a project compared to how it brings people into a project,” said Rogers. “Without [the glass component] it wouldn't be as popular. It's more successful when compared to ordinary structures.”

There are, however, modest alternatives. V-Kool, a clear, heat-blocking window film, for example, saves energy but doesn't change the exterior appearances of existing glass, says a spokesman for the colorless manufacturer. It is priced at about $10 to $12 a square foot, though volume reductions are offered. It's more expensive than traditional tinted glass film, which runs $4 to $6 per square foot, but it offers other benefits.

Conventional tinted film lets in 65 percent of solar energy while V-Kool only transmits 45 percent, according to the company. At the same time, it lets in 70 percent of the visible light while tinted film lets in about 35 percent.

As a result, users of tinted film have to compensate by using more artificial lighting in contrast with the amount of daylight that V-Kool, and other transparent coating systems, let in.

Mostly stand-alone retailers, such as Albertson's, Exxon and McDonald's are customers, the spokesman says. It has also been used at larger non-retail buildngs as well including the former Montgomery Ward headquarters in Chicago, the American Institute of Architects headquarters in Washington D.C. and at the Mumbai Marriott in India.

Apple of My Eye

Apple Computer has turned glass into an art form with its new Fifth Avenue glass cube, rising up from the surface in the shadows of Bergdorf Goodman and Trump Tower between 58th and 59th streets. The 32-foot cube (incorporating 538 sheets of glass) is only the tip of the berg, with the real 24/7 store in a 10,000-square-foot subterranean interior. The architect? CEO Steve Jobs himself, or at least, it's his vision.

Glass has been a vital part of Apple's design in other stores as well. Some sport glass staircases and full-height glass facades are the norm in both urban and suburban settings.
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Raise high the roof

Zlote Tarasy, being developed in Warsaw's downtown district around the train station, is a new mixed-use project that will serve as a year-round destination for shopping, leisure and entertainment. Called Golden Terraces in English, it is uniquely organized into a series of terraces and features an innovative canyon-like circulation path. But the most striking aspect of Zlote Tarasy is the roof design.

With clear spans ranging between 100 feet to 130 feet, the roof covers three levels and about 110,000 square feet designed to help the lively central plaza of Zlote Tarasy feel like an extension of a new adjacent park. The glass (less than 0.01 inches thick) creates the feeling of being outdoors while providing weather protection during the cold winter.

Starting with that design intent, suggesting overlapping tree canopies, the Jerde team said it turned to an inherently digital design paradigm and embarked on an extensive study of gravity and friction. By mimicking the processes of nature, the team knew it could create a roof that would look natural in form and would perform as efficiently as nature itself.

Using computer modeling to manipulate a group of virtual deflector spheres draped with “cloth” eventually produced the appropriate amount of undulation in the roof design.

The placement of the deflectors and drape of the cloth was modified until the sinuous aesthetic was achieved. It was further tweaked to accommodate practical needs such as interior height requirements, structural elements and proper storm drainage.

The team used physics-based computer programs designed for the creation of video game and film animation to determine the proper cloth-type. Knowing the correct properties for the cloth, Jerde could then provide the engineer on the project with a three-dimensional mesh they used to engineer the structural members.

The continuous thin shell of glass is supported by a series of tree-like columns rather than a bulky truss system. Elements of the project's interior architecture reflected the placement of the deflectors, providing a continuity and cohesiveness to the design of the whole.
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