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Design

Introduction

This development has sought to provide an all weather multi-purpose public assembly and education facility configured around a rectangular playing field and capable of hosting a range of events such as rugby union, rugby league, soccer, American Rules Football (Grid Iron), horse trials, Highland games, music concerts and other mass assembly events as deemed appropriate.

The development has sought to address allegorical and physical issues on the insertion of a large new highly visible building into the context of Dunedin City and its relationship to the landscape and the predominantly industrial neighbourhood. The aim is to create a modern, contemporary stage appropriate for hosting major events and representing Dunedin and Otago as a whole to the national and international community.

Architecture

The architectural character of the proposed multi-purpose events centre is inspired by both the local culture and its physical context. Set against the harbour and the surrounding hills the large angled roof form is the defining moment of the architecture. The façade and roof enclose the stadium by way of a translucent/transparent veil. This veil allows the building to take on a chameleon character with the skin responding to the changing moods of the day and night. During the day the translucent façade will shimmer in the changing environment from dawn to dusk with the sky contrast subtly altering the appearance of the façade. The daytime view would allow glimpses of the activity within yet provide a veil to the mass and bulk of the building.

Roof

The material proposed for the roof cladding is a transparent membrane technology, formally known as Texlon. Texlon comprises several layers of a space-age thermoplastic called ETFE that will be clamped to the roof structure and then filled with low pressure air to form large ‘cushions.’ The resulting ‘cushions’ are extremely strong and stable, and will allow large amounts of light – particularly in the photosynthetic UV light range – into the stadium, and therefore allow both the grass to grow naturally all year round and provide a sheltered venue.

ETFE is a close relative of the common compound PTFE – also known as Teflon and shares many of the same properties. In addition to having a ‘non-stick’ surface that will keep it clean, it has an extremely long lifespan and is not affected by salt water, acids, alkalis or other solvents present in the environment.

Items of interest:

  • The stadium will be designed to withstand minimum 90 knot winds without damage, which is equivalent toa Category 2 hurricane
  • Texlon ETFE cushions are custom designed and have been used in many public building-types, from airports to hospitals, galleries to youth hostels and, now for the first in the world, it is to be used to fully cover a multipurpose stadium
  • Texlon ETFE weighs less than 3kg per square metre
  • Texlon ETFE cushions are shatterproof
  • A Texlon ETFE system will give roughly the same thermal insulation as double glazing
  • ETFE has a melting temperature of approximately 260°C
  • Texlon ETFE structures can be easily lit using a variety of methods (including projection and LEDs)
  • For the different environments at this multipurpose stadium the simplest way to describe the acoustic effect of Texlon is to imagine that it is not there. The ETFE does not promote reverberation and does not reflect sound. The net effect would be as for an open air stadium.
  • As ETFE does not degrade over time – the material can be fully recycled and re-extruded to form new cushions
  • ETFE is made from a waste product from the mining industry and is not an oil-based product. It also requires very little heat in its manufacturing and is one of the most environmentally friendly materials available in the building industry
  • Can easily be repaired or patched
  • The Dunedin Multi Purpose Stadium will be the 3rd largest ETFE clad building in the world – the two others are the Beijing National Aquatic Centre and the Allianz Arena in Germany. It would be the largest ETFE clad building in the Southern Hemisphere

Turf

The turf that will grow under the ETFE roof will be natural and will be cared for in general terms similar to that of Carisbrook Stadium turf. As the Multi Purpose Stadium will not be exposed to the weather elements, the pitch will require a very carefully controlled watering and ventilation regime.

In conventional stadiums throughout New Zealand and the world, issues that arise for turf growth and management include large areas of the pitch being shaded by the grandstands. In the Dunedin winter, the extent of shading can be so severe that frost remains on parts of the pitch for several days and the impact of this on turf growth is significant.

One of the advantages of growing turf under the ETFE roof is the fact that the ETFE material distributes light much more uniformly over the turf surface and therefore hugely reduces the severe localised shading patterns that typically occur with solid-roofed grandstands.

To further understand the implications of growing turf under ETFE, Carisbrook Stadium Trust commissioned the turf consultant and the ETFE consultant to build a test rig in Dunedin. Inside the test rig, vigorous trials are being undertaken using artificial wear to understand the reaction the turf will have to everyday uses such as rugby matches, concerts etc and the recovery period required. Various light measurements are also being made.

To be able to develop a truly rounded opinion, the consultants set up an identical strip of turf right beside the test rig strip, without an ETFE roof. When tests were being undertaken in the test rig, identical tests were taking take place on the fully exposed turf. To date, results have shown that overall growth and recovery between both test areas has been similar under spring and summer conditions. The current round of testing will continue until the end of February, after which time it is planned that plots of different types of turfgrass will be established in the test rig to test turf performance through the crucial winter period.

Seating

The seating bowl will be organised into 4 stands.

The North, South and East stands will have a permanent seating capacity of 25,000 people and the West stand will have temporary seating for 5,000. However, the Stadium will have the capacity to attain 35,000 people seated and standing should the need arise.

Environmentally sustainable design (ESD)

Listed below are only some of the proposed ideas which the designers are considering to ensure the building is as environmentally sustainable as possible. As the team move into the detailed design phase these options will become clearer and greater certainty will be provided

ESD options which the designers are considering include:

  • Harvesting rainwater, and potentially greywater, for irrigation and toilet flushing
  • Solar hot water heating
  • Increased insulation to occupied conditional spaces
  • Use of materials with low embodied energy and emissions where possible
  • Public transportation initiatives and traffic management planning to reduce car usage.
  • Selection of mechanical and electrical systems to conserve energy
  • Natural ventilation at concourse level and back of the house areas where possible
  • Low energy lighting internally and externally