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Clear Roof Mock-Up In Place At New Vikings Stadium

Clear is the new retractable.

On Thursday, construction workers spent the afternoon installing an on-site mock-up of the ETFE roof that will ultimately cover 60% of the new Vikings stadium and provide fans with an outdoor feel in a climate-controlled environment.

Mock-ups are structural models built using the same construction procedures and materials that will be utilized on the final project. The models allow the project team to see the final project in a smaller version and to provide comments and feedback before the permanent installation begins.

Placement of ETFE on the stadium's roof is expected to begin next summer, and the stadium will be fully enclosed by late Fall 2015.

Given that the new material is now on site, we thought it might be time for an ETFE refresher course.

This week workers installed an on-site mock-up of the clear ETFE roof that will ultimately cover 60% of the new stadium, and also began the install of the ring beam.

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 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. 

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.

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.

Will snow/ice build up on the roof of the stadium?

Several characteristics of this roof are designed for Minnesota's climate. First, the slope of the stadium - rising from approximately 205 feet from grade in the east to 272 feet high in the west - will give the building a unique ability to shed snow. Secondly, the translucent ETFE material will allow more sunlight and radiant heat through the roof, which combined with the natural rise of heat from inside the stadium will help melt the snow and ice. Diverters will redirect it into gutters and collection basins located on the edges of the roof, keeping snow and ice from falling to the ground below.

What are some of the most notable facilities in the world using ETFE material?(Photos provided by Vector Foiltec) 

WaterCube - Beijing, China

Eden Project – Cornwall UK

Forsyth Barr Stadium - Dunedin, New Zealand

Allianz Arena - Munich, Germany

Click here to read the New Vikings Stadium Q&A article from the spring of 2013 for more on the roof, including photos of the above surfaces provided by Vector Foiltec.

Another Construction Milestone Reached

This week another construction milestone was reached as installation of the new stadium's ring beam began. Consisting of concrete with steel reinforcement running both horizontally and vertically, ring beams are a type of support used in construction to connect walls and columns together to increase the load capacity. In this case, the ring beam creates a structural diaphragm at the top of the stadium's columns in order to support the roof trusses and transfer the load to the columns.

Watch a video showing the beginning of the installation below:

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