TFE is the acronym for Ethylene-TetrafluoroEthylene Copolymer, which is a fluorocarbon-based material. It's a durable, adaptable and transparent plastic related to Teflon, which is opening new horizons for architects like at the Beijing Olympics (a swimming arena made out of bubbles, though to me it looks like a gigantic mattress, or a stadium knitted from steel framework seeming a weaver's nest) and beyond, like the massive tent -over 100.000m2- for the Khan Shatyry Entertainment Center located in Astana, the capital of Kazakhstan.

It was originally designed -around the 1970s, when DuPont invented a fluorocarbon-based polymer to be used as an insulation material in the aeronautics industry- to solve the needs of a material with high corrosion resistance and strength over a wide temperature range. DuPont did not initially care about marketing ETFE to architects. It was Stefan Lehnert -a German mechanical engineering, in his search for new sailing technologies- who saw building-material potentials in its transparency, and its self-cleaning and structural properties. In 1982, he founded Vector Foiltec -a design and manufacturing company specializing in the use of ETFE- in Bremen, Germany. The company's first project was the roof of a small pavilion at a zoo in Arnheim, Holland. Since then, ETFE has become increasingly popular, especially in Europe, and ETFE was widely used in office atriums, some educational buildings, medical facilities, exposition halls, and zoos across Britain and Germany. In 2000, the Eden Project, an environmental complex in Cornwall, Britain, designed by Grimshaw Architects and containing two gigantic geodesic conservatories covered in ETFE, was completed. The construction was acclaimed as an engineering marvel and created a wave of global interest.

The interesting property for architects is that the resin can be spun into a thin, durable film, which manufacturers such as DuPont (also Asahi Glass Company, which calls its version Fluon ) pack in rolls. It can be used in sheets or inflated into cushions. An example of its actual use is as pneumatic panels to cover the outside of the football stadium Allianz Arena in Germany or the Beijing National Aquatics Centre - the world's largest structure made of ETFE film (laminate). The panels of the Eden Project in Cornwall, England are also made of ETFE. Compared to glass, it's 1% the weight, transmits more light and costs 24% to 70% less to install. It's also resilient (able to bear 400 times its own weight, with an estimated 50-year life-span), self-cleaning (dirt slides off its nonstick surface), and recyclable. It is also able to stretch to three times its length without losing its elasticity. But sharp implements can puncture it -reason why it's used mostly for roofs. If the film tears, it can be patched with other pieces of ETFE. Strips can be heat-welded together like. This "sewing" method enables ETFE to be installed in pieces much longer and wider than glass: a strip of ETFE could be 54,90m long and 3,66m wide. When exposed to fire, it softens and shrinks away from the heat, naturally venting smoke out of a building.

In its typical usage, two or three layers are welded together and shipped flat to the job site, where they are inflated into panels or "pillows". These cushions require semi-continuous air pressure -to keep them stable and give them thermal properties- so most systems include thin hoses that plug into the cushions' sides. These air-supply lines connect to a computerized system that monitors the pressure within the cushions. This system can also feed air into, or eject air from, particular chambers or layers to let in more light or create more shade. In some installations, this is done automatically using light sensors. As many projects don't call for such a complexity Architects will have to evaluate, project by project, the convenience for using ETFE. It's certainly not advised to use it for small-scale or residential projects.

Acoustics can be another drawback. The cushion system, when used on a roof, can amplify the sound of rain because the tension in the cushion acts like a drum. Manufacturers have developed several noise-suppressing techniques, including layering polycarbonate sheets within ETFE cushions, but their use isn't widespread yet. Interior applications, such as walls within an office, present other sound issues. ETFE transmits more sound than glass or wood, making it not convenient for meeting rooms -or conference centres. In opposition, ETFE can be beneficial for self-contained, noisy areas like aquatic parks -sound bounces off the walls and floor and escapes through the roof.

Examples of brand names of ETFE are Tefzel by DuPont, Fluon by Asahi Glass Company and Texlon by Vector Foiltec.

Eden Project, 2001

(photos 1 to 10 of the Image Gallery)
These huge geodesic-domed greenhouses, part of an environmental complex in Cornwall, England, were originally supposed to be made of glass. But ETFE gave designers Grimshaw Architects a flexible, lightweight, and durable alternative. The result was an environment capable of housing plant species from around the world in tropical rainforest -and Mediterranean-style climates. With its 30.000m2 Eden was, at the time, the world's largest ETFE project and remains a defining image of "ETFE architecture".

Basel Stadium, 2001

(photos 11 to 16)
Home to Swiss soccer team, Basel FC, St Jakob Park was designed Herzog & de Meuron. The stadium gets its puffy shape from air panels made of ETFE film that surround its exterior. To create these panels (sometimes called pillows or cushions) dehumidified air is pumped between layers of film, which are heat-sealed. Here, the name of the city has been pieced in permanently using red ETFE film, but the rest of the translucent façade can be illuminated like a movie screen with projections of other images, even rival team logos.

Art Center College of Design, South Campus, 2004

(photo 17)
This unique space houses studios and galleries for Pasadena (Calif.) art students in a recycled wind tunnel. Printed ETFE film was used to clad three "sculptural skylights" that filter light to the underground facility. Foiltec, a leading ETFE manufacturing and design company, worked with Santa Monica (Calif.) firm Daly Genik Architects and graphic designer Bruce Mau to print the custom pattern. During the day, the pattern regulates the amount of light and heat transmitted below; at night, the skylights glow like lanterns.

Allianz-Arena, 2005

(photos 18 to 27)
This football stadium in Munich built for the 2006 World Cup is another Herzog & de Meuron's creation. Its nickname -"inflatable boat"- stems from its distinctive shape and the more than 2.800 ETFE-film air panels that cover its exterior. Like the Basel stadium, the arena's skin can be illuminated at night, glowing red, white, or blue depending on which team is playing.

Duisburg Meiderich Theater, 2005

(photo 28)
This outdoor theater built at a former steel foundry in Duisburg, Germany, needed a unique canopy roof to cover spectator seats in inclement weather. The clear ETFE panels rotate and slide from one side to the other using an electric motor -a neat trick that wouldn't be possible with a heavier and less flexible material like glass. ETFE's acoustic transparency meant that closing the roof would have not affected the performance or the audience's experience.

Beijing National Aquatics Center, 2007

(photos 29 to 32)
This building, dubbed the Watercube, will host swimming, diving, water polo, and synchronized swimming events at the Beijing Olympics in 2008. Sydney-based PTW Architects say they've echoed their design on patterns of cells and soap bubbles and used an iridescent box -covered in ETFE pillows- to create the bubble effect, though it really looks more like an out-of-scale mattress to me. With 70.000m2 and 4,000 ETFE pillows cladding its walls and roof, the Watercube houses five pools and seating for 17,000 spectators -the biggest project yet to use the material. It will also be one of the most energy-efficient buildings in the world. The blue film bubbles will help heat the building much like a greenhouse, trapping 90% of the solar energy that hits the building and recycling it to heat the pools and interior. ETFE was chosen over glass or fiberglass because it satisfied the project's engineering needs. Some bubbles in the design span 9m without any internal framing. Once the games start next year, officials will be able to transform the walls into a giant TV screen showing simultaneous projections of the swimming activities taking place inside.

Beijing National Stadium, 2007

(photos 33 to 40)
The Herzog & de Meuron-designed Olympics stadium is crafted out of woven steel and resembles a sturdy but intricate bird's nest. It's located about a half-kilometer from the Watercube. The project is one of contrasts, combining a muscular skeleton of entangled steel with soft ETFE cushions. The red ETFE pillows will fill the spaces between the framework's branches, helping to weatherproof the structure and to protect spectators from rain and wind.

han Shatyry Entertainment Center, 2008

(photos 41 & 42)
This 100.000m2 cultural complex located in Astana, the capital of Kazakhstan, will also lay on ETFE for its huge tent-like structure. The center, which is currently under construction, will include a wide range of shops, cafes and movie theaters, as well as a terraced park. Its top section, which resembles a gigantic tent upon a manmade mountain, will be covered by a vast curtain made of ETFE. London architecture firm Foster + Partners says the ETFE will let in light while protecting people from the area's harsh climate and enabling the park's use throughout the year. Although horrible, when finished, Khan Shatyry Entertainment Center will be the world's largest structure in ETFE.

LeMay Museum, 2009

(photos 43 & 44)
The new home for the Tacoma (Wash.) Harold E. LeMay Museum will house the largest privately owned collection of automobiles, motorcycles, trucks, and vehicle-related memorabilia in the world. The building's design will visually echo the curved roofs found on vintage cars and will incorporate ETFE in its ceiling and walls. Los Angeles-based Grant Architects says the cavity between the ETFE and the museum's exterior glass layer will function as a "smart wall," circulating air to increase the insulating properties of the building.

Earthpark, 2010

(photo 45)
The $155 million Earthpark project in Pella, Iowa, is an American-style Eden Project from the original Eden designers, Grimshaw Architects. ETFE will be used for the roof of this massive indoor rainforest biodome, which will house three Amazonian climates on 28.33 hectares. ETFE's natural insulating properties considerably enhance the project's green factor, too.

Properties for Ethylene-Tetrafluoroethylene Copolymer (ETFE)

Source: www.goodfellow.com