ETFE and the New Look of Plastic

Building with Ethylene Tetrafluoroethylene

In daylight, ETFE cladding can look like panels of silver aluminum
The SSE Hydro at Scottish Exhibition and Conference Centre, Glasgow, Scotland. Craig Roberts/Getty Images (cropped)

ETFE is an abbreviation for Ethylene Tetrafluoroethylene, a translucent polymer sheeting that is used instead of glass and hard plastic in some modern buildings. ETFE is usually installed within a metal framework, where each unit can be lighted and manipulated independently. Light sources can be on either side of the plastic cladding.

Compared to glass, ETFE transmits more light, insulates better, and costs 24 to 70 percent less to install. ETFE is only 1/100 the weight of glass, and it has properties that make it more flexible as a construction material and a medium for dynamic illumination.

Key Takeaways: ETFE

  • ETFE (Ethylene Tetrafluoroethylene) is an industrial-strength construction plastic used for exterior cladding since the 1980s.
  • ETFE is strong and lightweight. It is often applied in layers that are welded together around the edges and held by a metal framework.
  • Because it is safer and more adaptable than glass, non-rip ETFE is often used as a replacement for glass.
  • Commercial uses of ETFE include many sports arenas and entertainment venues. Dynamic lighting of this plastic has been a successful feature of ETFE architecture.

Uses of ETFE

The SSE Hydro in Scotland, part of the design portfolio of British architect Norman Foster, was completed in 2013 as an entertainment venue. In the daylight, the ETFE cladding may lack excitement but be functional by allowing natural light to the interiors. After dark, however, the building can become a light show, with interior lighting shining out or exterior lights around the frames, creating surface colors that can be changed with the flip of a computer program.

For other venues, rows of lights surround the plastic panels. The ETFE cusions on the Allianz Arena in Germany are diamond shaped. Each cushion can be controlled digitally to display red, blue, or white lights — depending on which home team is playing.

Close-up of small red lights surrounding ETFE plastic panels
ETFE Exterior Panels on the Allianz Arena. Lennart Preiss/Getty Images

This material has been called a fabric, a film, and a foil. It can be sewn, welded, and glued together. It can be used as a single, one-ply sheet or it can be layered, with multiple sheets. The space between the layers can be pressurized to regulate both insulating values and light transmission. Light can also be regulated for local climates by applying nontransmittable patterns (e.g., dots) during the manufacturing process. With dark dots imprinted on the translucent plastic, light rays are deflected. These application patterns can be used in conjunction with layering — using photo sensors and computer programs, the location of the "dots" can be strategically moved by controlling the air between layers, by "stretching or sagging" the material, which positions the dots to block where the sun is shining through.

white by day, sculpted exterior of Allianz Arena glows red at night
Allianz Arena Dynamic Lighting. Lennart Preiss/Getty Images (cropped)

Computer systems can also regulate dynamic lighting effects for ETFE structures. When the exterior of the Allianz Arena is red, FC Bayern Munich is the home team playing in the stadium — their team colors are red and white. When the TSV 1860 München soccer team plays, the colors of the stadium change to blue and white — that team's colors.

Characteristics of ETFE

ETFE is often called a miracle construction material for tensile architecture. ETFE is (1) strong enough to bear 400 times its own weight; (2) thin and lightweight; (3) stretchable to three times its length without loss of elasticity; (4) repaired by welding patches of tape over tears; (5) nonstick with a surface that resists dirt and birds; (6) expected to last as long as 50 years. In addition, ETFE doesn't burn, although it can melt before it self-extinquishes.

Because of its strength and ability to transmit UV rays from the sun, ETFE is frequently used in sports venues that desire healthy, natural turf athletic fields.

Disadvantages of ETFE

Everything about ETFE is not miraculous. For one thing, it is not a "natural" building material — it's plastic, after all. Also, ETFE transmits more sound than glass, and can be too noisy for some places. For a roof subject to raindrops, the workaround is to add another layer of film, thus decreasing the deafening drumbeats of rain but increasing the construction price. ETFE is usually applied in several layers that must be inflated and require steady air pressure. Depending on how the architect has designed it, the "look" of a building could drastically change if the machines that supply the pressure fail. As a relatively new product, ETFE is used in large commercial ventures — working with ETFE is too complex for small residential projects, for the time being.

The Full Life Cycle of Building Materials

How is it that a synthetic plastic film has come to be known as the building material of sustainability?

When choosing building products, consider the life cycle of the materials. For example, vinyl siding may be recycled after its usefulness, but what energy was used and how was the environment polluted by its original manufacturing process? Concrete recycling is also celebrated in the environmentally friendly construction world, but the manufacturing process is one of the prime contributers to greenhouse gasses. A basic ingredient in concrete is cement, and the U.S. Environmental Protection Agency (EPA) tells us that the manufacturing of cement is the third largest industrial source of pollution in the world.

When thinking of the life cycle of glass production, especially compared to ETFE, consider the energy used to create it and the necessary packaging to transport the product.

Amy Wilson is "explainer-in-chief" for Architen Landrell, one of the world's leaders in tensile architecture and fabric systems. She tells us that manufacturing ETFE causes little damage to the ozone layer. "The raw material associated with ETFE is a class II substance admitted under the Montreal treaty," Wilson writes. "Unlike its class I counterparts it causes minimal damage to the ozone layer, as is the case for all materials used in the manufacturing process." Reportedly creating ETFE uses less energy than making glass. Wilson explains:

"The production of ETFE involves the transformation of the monomer TFE in to the polymer ETFE using polymerisation; no solvents are used in this water based procedure. The material is then extruded to varying thicknesses depending on application; a process which uses minimal energy. Fabrication of the foil involves welding large sheets of the ETFE; this is relatively quick and again a low energy consumer."

Because ETFE is also recyclable, the environmental culpability is not in the polymer, but in the aluminum frames that hold the plastic layers. "The aluminium frames do require a high level of energy for production," Wilson writes, "but they also have a long life and are readily recycled when they reach their end of life."

Examples of ETFE Structures

A photo journey of ETFE architecture quickly dispels the notion that this is a simple plastic cladding material you might put over your roof or boat on a rainy day. The Swiss architecture team of Jacques Herzog and Pierre de Meuron created a sculpted look for the Allianz Arena (2005), one of the most beautiful ETFE structures in München-Fröttmaning, Germany. Mangrove Hall (1982) at Royal Burgers' Zoo in Arnhem, the Netherlands, is said to be the first application of ETFE cladding. The Water Cube venue (2008) built for the Beijing, China Olympics brought the material to the attention of the world. The biodome Eden Project (2000) in Cornwall, England created a "green" tinge to the synthetic material.

side view of curved sports stadium, sculpted exterior of inflated ETFE plastic panels, looking like a white treaded tire on its side
Allianz Arena Designed by Herzog & de Meuron, 2005, Munich, Bavaria, Germany. Chan Srithaweeporn/Getty Images (cropped)

Because of its flexibility and portability, temporary structures such as the summer Serpentine Gallery Pavilions in London, England have been of late at least partially created with ETFE; the 2015 pavilion in particular looked like a colorful colon. The roofs of modern sports stadia, including the U.S. Bank Stadium (2016) in Minneapolis, Minnesota, are often ETFE — they look like panes of glass, but the material is really safe, non-rip plastic.

Colorful ETFE plastic forms the walls and ceiling of a small cafe
Temporary Summer Pavilion in London's Hyde Park by Spanish Architects José Selgas and Lucia Scano, 2015. Lionel Derimais/Getty Images (cropped)

Plastics, the Industrial Revolution Continues

The du Pont family emigrated to America shortly after the French Revolution, bringing with them 19th century skills in making explosives. Using chemistry to develop synthetic products never stopped within the DuPont company, creators of nylon in 1935 and Tyvek in 1966. When Roy Plunkett worked at DuPont in the 1930s, his team accidentally invented PTFE (polytetrafluoroethylene), which became Teflon.® The company, who considers themselves a "pioneer of polymer science with a legacy of innovation," is said to have created ETFE in the 1970s as an insulation coating for the aerospace industry.

The tensile architecture of Prizker laureate Frei Otto in the 1960s and 1970s was an inspiration for engineers to come up with the best material to use for what builders and architects call "cladding," or the material that we might call exterior siding for our homes. The idea for ETFE as a film cladding came in the 1980s. Engineer Stefan Lehnert and architect Ben Morris co-founded Vector Foiltec to create and market Texlon® ETFE, a multi-layered system of ETFE sheets and architectural cladding. They didn't invent the material, but they did invent the process for welding together sheets of ETFE — and giving a building the layered look.

Sources

  • Birdair. Types of Tensile Membrane Structures. http://www.birdair.com/tensile-architecture/membrane
  • Birdair. What is ETFE film? http://www.birdair.com/tensile-architecture/membrane/etfe
  • Dupont. History. http://www.dupont.com/corporate-functions/our-company/dupont-history.html
  • Dupont. Plastics, Polymers, and Resins. http://www.dupont.com/products-and-services/plastics-polymers-resins.html
  • EPA. Cement Manufacturing Enforcement Initiative. https://www.epa.gov/enforcement/cement-manufacturing-enforcement-initiative
  • Wilson, Amy. ETFE Foil: A Guide to Design. Architen Landrell, February 11, 2013, http://www.architen.com/articles/etfe-foil-a-guide-to-design/, http://www.architen.com/wp-content/uploads/architen_files/ce4167dc2c21182254245aba4c6e2759.pdf