CHALLENGE. Forsyth Barr Stadium is located in Dunedin, New Zealand, at 45 degrees South and is the most southerly professional stadium in the world. With high average annual rainfalls, a cooler climate, and an existing stadium which was falling below standards, the NZ Rugby Union decided it was time for a new stadium. And of course the Rugby World Cup was looming.
When the decision was made to commission a new stadium, an all-weather venue was the obvious choice, but given the modest size of the city (119,000 people), it was difficult to justify the cost of an enclosed venue for a handful of sporting matches. It was eventually agreed that the stadium be used for a variety of purposes, including sporting, cultural, entertainment and educational uses.
The design team was thus faced with the challenge of creating a stadium with a natural grass pitch growing under a fully fixed roof. Populous’ broad experience with covered venues around the world brought valuable insights to the design of the new stadium, and for two years the design and research team studied different materials for roofing the stadium and their effect on optimal grass growth. Eventually ETFE (ethylene tetrafluoroethylene) – a transparent polymer originally developed for the space industry – was developed. Following this research, the stadium design was primarily dictated by the requirement to maximize sun strike levels and natural ventilation. The ETFE covers the roof, and part of the facades, and the stands on the Northern end are lower to allow maximum sun light onto the pitch. The end facades are raised 5m above ground to allow fresh air across the pitch.
INNOVATION. Forsyth Barr Stadium is the world’s only permanently covered stadium to boast a natural turf playing field. Whilst ETFE is not a new product, this is the first time its UV translucent properties have been put to use in a stadium, creating the largest ETFE covered structure in the Southern Hemisphere. Dunedin’s cold and wet climate makes the roof an essential feature of the stadium to encourage crowds to attend live events.
IMPACT. During the research and early design stages, an ETFE test rig was built on site to monitor grass growth both under the rig and outside it. Toward the end of the testing phase, it was discovered that the grass under the rig was stronger and healthier than the grass surrounding it, withstanding several high impact tests by local rugby. In September 2011, the stadium played host to a number of pool matches during the NZ Rugby World Cup and received great critical acclaim for the condition of the pitch and the levels of spectator comfort within an enclosed venue. In November 2011, Elton John was the first entertainer to perform at Forsyth Barr Stadium, this being his only New Zealand show, and a great boost to the Dunedin community.
The innovative use of ETFE and the success of the grass growth sets a new benchmark for North American and Northern European venues for the feasibility of grass growth under an enclosed structure.