Recap
While the Vikings' owners wanted an outdoor stadium, the state and local governments would only provide funding for an indoor stadium capable of hosting major events like the Super Bowl and the Final Four. A retractable roof was the trend in 2010s football stadiums. However, retractable roof facilities are not typically designed for the roof to be opened and closed in sub-freezing conditions. When built in temperate climates, retractable roofs are generally kept closed throughout the winter months, both to reduce the stress on the roof and its components and also to reduce or eliminate the need to winterize the stadium's interior. In contrast, to be of any competitive on-field advantage to the Vikings, a retractable roof facility would have needed to be designed to operate in a Minnesotan winter so as to allow the Vikings to play a home game outdoors during the NFL playoffs. Eventually, this design was deemed too expensive.
Architecture firm HKS, Inc., also responsible for the Dallas Cowboys' AT&T Stadium and the Indianapolis Colts' Lucas Oil Stadium, decided to go for a lightweight translucent roof and glazed entrances with giant pivoting doors, aiming to get as much natural light from the outside as possible. The roof is made up of 60% Ethylene tetrafluoroethylene (ETFE), a fluorine-based clear plastic, and is the largest in North America, spanning 240,000 square feet (22,000 m2) supplied and installed by the firm Vector Foiltec. ETFE's low R-factor and the roof's slanted design, inspired by Nordic vernacular architecture, allows the stadium to endure heavy snow loads. Snow accumulates in areas that are more safely and easily accessible, and also moves down the slanted roof into a heated gutter, the water from which drains to the nearby Mississippi River.
The translucent roof and large wall panels also give fans a view of downtown Minneapolis. The glass operable wall panels allow the stadium to experience some of the outdoor elements while providing protection from the snow, rain, and the cold winter weather. The stadium is aligned northwest and the elevation at street level is approximately 840 feet (255 m) above sea level.
