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New Vikings Stadium Q&A: The Clear Roof

Posted May 20, 2013

Following the unveiling of the new Vikings stadium design, we've received numerous questions from fans and members of the media regarding various design elements and specifics. While we cannot answer all of your questions at this time because discussions continue about some of the final design details, we will do our best to do a Q&A series to address as many questions as possible. You can submit questions for future Q&As here.

For this first installment, let's dive into some details of ethylene-tetraflouroethylene, or ETFE, which will be used for the entire south side of the new stadium's roof. I'm clearly not an engineer, so big thanks goes to Jay Caddell, vice president at HKS, and Edward Peck, vice president at structural and building skin engineering firm Thornton Tomasetti, for providing the following information.

What is ETFE?

ETFE is a co-polymer resin that is extruded into a thin film. The plastic-like material is transparent but can be treated to be translucent, is extremely light-weight, very durable and resistant to corrosion. In an architectural application ETFE is typically used in a multi-layer pneumatic system.

What is the life/longevity of ETFE?

ETFE does not degrade with exposure to UV light, atmospheric pollution, harsh chemicals or extreme temperatures. The material has withstood extensive testing within extreme environments, and is expected to have a 30-50 year life expectancy while requiring minimal maintenance. The true life-cycle of ETFE is not known as the oldest applications are just hitting the 30-year mark with little to no replacement of system components.

How does ETFE handle weight/pressure?

Despite its weight (1/100 the weight of glass) ETFE handles snow/wind loads very well. In sheet form, it can stretch three times its length without losing elasticity. For an example of ETFE's strength, view this photo of a Volkswagon being lowered on a multi-layered pneumatic ETFE system.

How do you clean ETFE?

ETFE systems are extremely low maintenance. The surface of the foil is non-stick and non-porous, which allows the natural action of rain to clean the surface. Deposits of dirt, dust and debris remain unattached and are washed away in the rain, meaning ETFE effectively self-cleans with virtually no need to clean externally.

What are some of the most notable facilities in the world using ETFE material?

WaterCube - Beijing, China (Photo provided by Vector Foiltec)

Eden Project – Cornwall UK

Forsyth Barr Stadium - Dunedin, New Zealand (Photo provided by Vector Foiltec)

Allianz Arena - Munich, Germany (Photo provided by Seele Cover)

New Stadium ETFE Facts

  • The new stadium will have the largest transparent ETFE roof in North America, spanning 240,000 square feet. 
  • This will be the only stadium in the nation with a clear ETFE roof. 
  • Because of the angles of the roof, ETFE material on the south side will make up 60% of the entire roof, while hard metal deck on the north side will account for the remaining 40%. 
  • The ETFE will cover approximately 60% of the field but the angle of the roof will allow sunlight over the entire field. 

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