Why is ETFE the material of choice for U.S. stadia?
"Ethylene tetrafluoroethylene" doesn't exactly roll off the tongue. Thankfully "E-T-F-E" does. The material—commonly referred to by its acronym—is all the rave within the architecture world right now, mostly notably seen in contemporary stadia design.
A Project Engineer at New York firm, Thornton Tomasetti, Alloy Kemp spoke to The Architect's Newspaper about the material's key role in stadia projects such across the U.S. These included: the Banc of California Stadium (for the Los Angeles Football Club, MLS) and the U.S. Bank Stadium (for the Minnesota Vikings).
With regard to the latter example, the stadium makes use of a 240,000-square-foot transparent ETFE roof—the largest of its kind in the country. Here, transparency facilitates clear views outside and bathes the playing field in natural light. This also aids climate control within the space, a key factor when growing pitch-perfect grass. While the ETFE system facilitates solar gains, excess heat vents at the stadium's peak supplement ventilation requirements.
The latter meanwhile uses the material expose the structure as a roof clad with 190,000 square feet of ETFE film reveal long-span cantilevers. Kemp pointed out that the material lets a full spectrum of UV light through, something "which aids in plant growth." She also cited the material's "high span to weight ratio" and "its ability to warp" that allow "lighter and sparser structure," as a main reason for its selection. Additionally, kemp added that a low friction coefficient means with regular rainfall, it is capable of cleaning itself with little maintenance necessary.
Another stadium, this time for the LA Rams team, also makes use of ETFE. The stadium, designed by New York–based HKS, features a giant triangular roof supported by thick columns and made of the material. This super-roof also spans across an adjacent outdoor lobby called “champions plaza” to be used as a communal gathering spot for game day spectators. For year-round events, the stadium features a transparent ETFE canopy covering nearly 19 acres. The canopy allows all sides of the building to remain open to the air, allowing natural breezes to pass through while protecting the up to 80,000 patrons from inclement weather.
Alloy Kemp will be speaking at the next Facades+ conference in New York on April 6 There she and Edward Peck of Forum Studio will discuss ETFE's use in the LA Football Club and Minnesota Vikings stadiums as well as in the DS+R's Hudson Yards Culture Shed. Seating is limited. To register, go to facadesplus.com.