ETFE and the New Look of Plastic

Building with Ethylene Tetrafluoroethylene

In daylight, ETFE cladding can look like panels of silver aluminum or like pillow puffs or bubble wrap if not stretched tightly
The SSE Hydro Designed by Norman Foster, Glasgow, Scotland. Photo by Craig Roberts/Photolibrary/Getty Images (cropped)

ETFE is another way of saying Ethylene Tetrafluoroethylene, a translucent polymer sheeting that is used instead of glass and hard plastic in some modern buildings. Compared to glass, ETFE (1) transmits more light; (2) insulates better; (3) costs 24 to 70 percent less to install; (4) is only 1/100 the weight of glass; and (5) has properties that makes it more flexible as a construction material and a medium for dynamic illumination. ETFE is usually installed within a metal framework, where each unit can be lighted and manipulated independently.

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, which deflect light rays. These application patterns can be used in conjunction with layering, moving the location of the "dots" by "stretching or sagging" the material.

Why ETFE Is Used in Tensile Architecture

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.

Plastics, the Industrial Revolution Continues

The famous exchange from the 1960s movie The Graduate comes to mind: "One word. Are you listening? Plastics. There's a great future in plastics."

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 as an insulation coating for the aerospace industry.

The tensile architecture of German 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. Their architectural cladding system can be seen in this YouTube video.

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.

Examples of ETFE Structures

Mangrove Hall (1982) at Royal Burgers' Zoo in Arnhem, the Netherlands, is said to be the first application of ETFE cladding. The Water Cube, the National Aquatic Centre in Beijing, China brought the material to the attention of the world. The biodome Eden Project in Cornwall, England has brought a "green" tinge to the synthentic material. 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 in Minneapolis, Minnesota, are often ETFE - they look like panes of glass, but it is safe, non-rip plastic.

Shown here is the SSE Hydro in Scotland, part of the design portfolio of British architect Norman Foster. Completed in 2013 as an entertainment venue, the ETFE cladding in daylight can lack excitement but be functional by allowing natural light to the interiors. ETFE cladding at night, however, 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.