With hot summers and cold winters, Minnesota’s location in the upper midwestern US means it experiences some of the widest variety of weather in the United States.
The dramatic slant of the Minnesota Vikings new stadium – featuring the nation’s largest translucent ethylene tetrafluorethylne (ETFE) roof – should enable NFL games to continue irrespective of the weather.
Five times in the history of the Vikings’ current home, the Metrodome, heavy snows or other weather conditions have significantly damaged the roof and in four instances caused the air-supported roof to deflate.
The steeply lofted steel roof of the Vikings’ new home is the result of collaboration between architects HKS Sports & Entertainment Group and structural engineers Thornton Tomasetti.
Eschewing the network of overhead beams that would have been necessary with a traditional ceiling will give the new stadium one of the lightest hard roofs in the world.
A single monumental steel ridge truss spanning 970 feet along the length of the field will provide the primary support for the roof structure. On the south side of the ridge, the roof will be clad with a clear ETFE system covering a massive 240,000 square feet.
This transparency will afford panoramic views of the outdoors, allowing natural light to infuse the interior of the stadium and produce additional solar gain to warm the stadium.
Excess heat will be vented out of the stadium’s peak as part of a coordinated sustainability strategy. The other side of the ridge will be a traditional steel deck and membrane roof, while the angled cantilever should let nature and gravity take its course and cause falling snow to simply slide off.
The twofold strategy to prevent snow accumulation on the old Metrodome roof was significantly more complicated. When snow accumulation was expected, hot air was pumped into the space between the roof’s two layers.
Workers also climbed onto the roof and used steam and high-powered hot-water hoses to melt snow. Although the inside of the stadium was also heated to nearly 80 degrees Fahrenheit to combat an incoming storm, it was unable to prevent a collapse in December 2010.
The new venue features a series of 95-foot-tall glass doors – the largest operable panels in the world, in a glass endwall that pivot to provide natural ventilation and access to the west plaza.
The seven-level superstructure will consist of precast concrete seating units and cast-in-place concrete frames and concourses. It will include 115 suites and 9,000 club seats, while a lower suite level will be the closest to the field of any NFL venue.
The Minnesota Sports Facility Authority is the developer and Mortenson Construction is the general contractor for the 1.7 million square foot, 64,000-seat stadium, which has already broken ground. Scheduled for completion in time for the 2016 NFL season, the project will seek LEED certification.