The NFL’s Minnesota Vikings franchise is aware what a heavy accumulation of snow can do. Late in the 2010 season, the Twin Cities were hit by a blizzard, and 17 inches of snow came to rest on the Metrodome’s air-supported Teflon and fiberglass roof. All the weight and moisture caused the roof to puncture and collapse. The stadium was repaired the next summer for $22.7 million.
For the team’s new stadium, which was designed by HKS Architects and is set to open next fall, the team is ensuring that the roof will hold up to rough northern conditions. U.S. Bank Stadium will have an ETFE (ethylene tetrafluoroethylene) pneumatic roof, a durable, flexible material made of a polymer similar to Teflon, as the Minneapolis Star-Tribune reports. ETFE is 1/100th the weight of glass and can stretch three times its length without losing elasticity.
The ETFE pillows are still supported by air, but they are also backed by a steel structure and won’t sink due to a loss of air pressure. The panels can be punctured by sharp objects but are easy to patch, and the nonstick surface and steep angle will help prevent snow from piling high.
ETFE also is lightweight and translucent, allowing natural light to enter for a sense of openness. Domed stadiums of the past, like the Metrodome, were known for being dark and cavernous.
Roughly 248,000 sf of the roof will be composed of ETFE; the remaining portion will be a steeply-pitched hard roof, but sunlight will still angle over the entire field. According to the Vikings’ website, ETFE will not degrade when exposed to UV light. Altogether, U.S. Bank Stadium will cost just more than $1 billion to build.
ETFE has previously been installed at venues like the Beijing National Stadium in China, the Eden Project in Cornwall, U.K., and Allianz Arena in Munich.