Sustainable Roofs and Facades for Sports Structures

Summary

In broad terms, 'sports facilities' are structures built for the conduct of sports activities. Permanent, semi-open or enclosed structures (stadium, sports hall, arena, velodrome, indoor swimming pool, etc.) that provide the sports venues necessary (field, course, etc.) for team sports (football, basketball, baseball, ice hockey, etc.), athletics, gymnastics, cycling, winter sports, swimming and other sports competitions, together with the spatial arrangements required for their viewing and conduct, are grouped under this heading. In the world, particularly following 1990, as a result of globalizing world economics, larger budgets have been allocated to sports, particularly football, and sports facilities, especially stadiums, have begun to transform. Today, with the "sustainable architecture" approach gaining support across all areas of architecture as a solution to increasingly global environmental problems, the concept of "sustainability" has begun to gain importance for sports facilities as well. Particularly in the last decade, sports facilities referred to by many adjectives such as "sustainable", "environmentally friendly", "energy efficient", "ecological" and "green" have been constructed. In this study, notable examples of structures defined as "sustainable sports facilities" are examined chronologically in terms of the sustainable properties of roof and facade systems. In the structures examined, 'sustainability qualities' for roof and facade use have been established in outline and examined with reference to existing structures.

1. Introduction

In broad terms, 'sports facilities' are structures built for the conduct of sports activities. Permanent, semi-open or enclosed structures (stadium, sports hall, arena, velodrome, indoor swimming pool, etc.) that provide the sports venues necessary (field, course, etc.) for competitions in many sports disciplines including team sports (football, basketball, baseball, ice hockey, etc.), athletics, gymnastics, cycling, winter sports and swimming, together with the spatial arrangements required for their viewing, are grouped under this heading. In the world, particularly following 1990, as a result of globalizing world economics, larger budgets have been allocated to sports, especially football, and sports facilities, particularly stadiums, have begun to transform. Today, as the importance and prevalence of global sports organizations increase, sports facilities are becoming increasingly diverse and prestige structures in line with the professionalization of sport. With the "sustainable architecture" approach gaining support across all areas of architecture as a solution to increasingly global environmental problems, the concept of "sustainability" has begun to gain importance for sports facilities as well. Particularly in the last decade, sustainable sports facilities referred to by many adjectives such as "environmentally friendly", "energy efficient", "ecological" and "green" have been constructed. In this study, these structures will be examined in outline with a focus on the sustainability qualities of their roofs and facades.

2. Sustainable Roofs and Facades in Sports Facilities

Today, around the world, there are many sports facilities, both completed and under construction, that are described architecturally as "sustainable". Notable examples of the roof and facade systems of these structures, which can be defined as "sustainable sports facilities" by general consensus, will be discussed below in chronological order in terms of 'sustainability' qualities. 2.1. Allianz Arena (Munich, Germany, 2005, Herzog & de Meuron) is a football stadium with a capacity of 71,137 (Figure 1.a). The structure, which has the world's largest membrane shell [1], features 2,874 diamond-shaped pneumatic ETFE (ethylene tetrafluoroethylene) panels on its facade and roof (Figure 1.b). The pneumatic ETFE panels are made of 0.2 mm thick ETFE film with a weight of 350 g/m², UV transmittance of 95% and visible light transmittance of 93%. In the building's design, providing the necessary sunlight for natural grass was an important criterion. Because Munich is located at high latitudes, solar rays arrive at an angle. For this reason, ETFE was preferred on the roof and facade to protect spectators from external elements while making effective use of daylight [2]. Transparent ETFE with 98% UV light transmittance was used in the southern sections to promote grass growth. During matches, retractable roller sunshades are embedded in the roof to protect spectators from the sun. ETFE panels can be illuminated in white, red and blue according to the home team [1]. 2.2. Beijing National Swimming Centre (Beijing, China, 2007) is a swimming sports complex built for the 2008 Summer Olympic Games. More commonly known as the "Water Cube", the structure employs 100,000 m² of pneumatic ETFE cushions covering the roof and facade. Swimming pools are buildings with high heating requirements. The structure's ventilated cavity ETFE shell transmits 90% of incident solar radiation, facilitating the heating of interior spaces and pools and thus reducing the building's heating costs. To provide resistance and insulation against wind loads, pneumatic ETFE cushions inflated with low-pressure air are stretched within aluminum frames supported by a lightweight steel structure. The working principle of the ventilated cavity between the inner and outer ETFE cushion walls is shown in Figure 2.a [3]. The facade appearance of the ETFE cushions (Figure 2.b) is designed on the basis of the natural geometry of adjacent soap bubbles. ETFE material use in sustainable sports facilities is examined in the conclusion section together with other examples. 2.3. Richmond Olympic Oval (Richmond, Canada, 2008, Cannon Design) is a multipurpose sports hall built for the 2010 Winter Games. The LEED Silver-certified structure's 25,900 m² wooden roof was constructed with ecological materials. The roof uses Douglas fir trees that were cut and discarded from regional forests due to an outbreak of the 'mountain pine beetle' that damages North American forests (Figure 3.a). The use of this wood in the structure has been beneficial in reducing the economic damage that the local economy suffered from the beetle infestation [4]. The roof design is reminiscent of the curved wings of the heron, the city's symbol; it consists of 15 glued laminated timber beams spanning 100 metres wide and 452 corrugated wood panels passing between them. The roof also features a rainwater collection system. The building's facade is designed to be transparent to light (Figure 3.b). 2.4. Kaohsiung Dragon Stadium (Kaohsiung, Taiwan, 2009, Toyo Ito) is the world's first stadium to meet its entire energy needs from solar energy (Figure 4.a). Completely covering the roof of the structure, 8,844 dragon-scale-like arranged BIPV (Building-integrated photovoltaic) panels cover a total of 14,155 m² (Figure 4.b). This PV system generates up to 1,000 kWh per hour [5] with an annual output of 1.14 GWh, preventing 600 tonnes of CO₂ emissions per year [6]. In the 55,000-capacity structure, another sustainable feature of the roof is the energy-efficient, lightweight roof structure made of spiral high-strength steel beams and prefabricated concrete that optimizes material use. All materials used in the structure are recyclable/reusable materials and were manufactured in Taiwan [6]. Photovoltaic (PV) system use in sustainable sports facilities is examined in the conclusion section together with other examples. 2.5. Aviva Stadium (Dublin, Ireland, 2010) is a football and rugby stadium with BS8901 sustainability certification, with a capacity of approximately 50,000 people (Figure 5) [7]. To allow continuous daylight into the interior and field, the roof and facade employ transparent polycarbonate cladding. The undulating and transparent design of the building's roof ensures that neighboring residential and commercial buildings also benefit maximally from daylight. The roof also collects rainwater in a 320,000-litre storage system for use in field irrigation and toilets – capable of meeting 7 days' watering requirements. In the stadium building, ground granulated blast furnace slag was used instead of Portland cement in concrete, reducing CO₂ emissions in the building's production process by 4,000 tonnes [7]. 2.6. Marlins Park Baseball Stadium (Miami, USA, 2012, Populous) is a LEED Gold-certified baseball stadium. The structure consumes 22% less energy than similar buildings due to its energy-efficient building envelope – and mechanical, electrical, heating and cooling systems [8] (Figure 6.a). The 8,000-tonne retractable roof of the structure, designed to withstand the region's strong storms, is operated by a 'regenerative motor system' (a motor that generates electricity by utilizing system load instead of consuming electricity during braking, stopping, etc. and supplies power source), which significantly reduces energy consumption. The electric cost for opening and closing the roof is less than 10 dollars due to this energy-saving system [8] (Figure 6.b). The surface area of the moveable portion of the roof structure is 31,400 m². The building's facade uses large windows and sliding glass panels to provide abundant natural lighting and views of the city.   2.7. Brasilia Stadium (Brasilia, Brazil, 2013, Castro Mello) is the world's first stadium to be a candidate for LEED Platinum certification – the review process is ongoing (Figure 7). The most important feature of the building's roof is its titanium dioxide (TiO₂)-coated photocatalytic membrane. In addition to its 'self-cleaning' property with rain, the photocatalytic membrane demonstrates 'air-cleaning' properties by neutralizing nitrogen oxides that cause air pollution [9]. The facade, which also collects rainwater, is designed with abundant openings to provide air circulation to circulation areas and into the stadium. Materials from the previous stadium built in 1974 that was replaced have been recycled and used in the structure. PV system use is also planned for the roof. At the outer edge of the building's circular roof, there is a 6.7 m wide ring-shaped reinforced concrete slab. Serving as a pressure ring for the photocatalytic membrane, this reinforced concrete slab accommodates 9,600 PV panels of 2,500 kW capacity [10][11]. The PV system, with polycrystalline silicon PV modules installed over 15,000 m², is calculated to reach up to 3,000 MWh/year capacity [12].

3. Conclusion

The main sustainability-related qualities of roofs and facades in the structures examined in the study are: 1) Rainwater collection on roof, 2) Use of ecological materials, 3) Lightweight, energy-efficient roof/facade structure, 4) PV system use, 5) Effective daylight use, 6) Energy-efficient retractable roof, 7) Self-cleaning/air-cleaning. The evaluation of the examined structures in terms of 'sustainability qualities' is presented in Table 1. As can be seen, "lightweight, energy-efficient roof/facade structure" and "effective daylight" use are the primary sustainability qualities for sustainable sports facilities. Another notable point is the increasing prevalence of PV (photovoltaic) systems in sports facilities for electricity generation. Significant examples of sports facilities using PV systems worldwide are reviewed and listed in Table 2 with system characteristics, ranked by annual power generation capacity. In all these structures, PV systems are integrated into the roof; no examples of PV systems integrated into facades were found. The structures feed electricity generated while not in use for sports activities back to the grid. Among sports facilities with PV systems, the largest in terms of energy production capacity is Kaohsiung Dragon Stadium (Kaohsiung, Taiwan, 2009) examined in this study, and the second is Stade de Suisse Wankdorf (Bern, Switzerland, 2005) (Figure 8.a). Both structures were built with roof-integrated PV systems that played an important role in design criteria. While active integration of PV systems into the design process is becoming increasingly common, retrofitting PV systems to existing sports facilities – particularly stadiums – is also a widespread practice. For example: Bentegodi Stadium (Verona, Italy), built in 1963, was renovated with PV system installation in 2009 (Figure 8.b), and Easy Credit Stadium (Nuremberg, Germany), built in 1928, was renovated with roof-mounted PV system in 2006. Bentegodi Stadium currently ranks third among sports facilities with PV systems in terms of energy production capacity. The Brasilia Stadium examined in this study has not been included in the list due to incomplete PV system installation; when it becomes operational, this structure will rank among the top in the list. ETFE (ethylene tetrafluoroethylene) material use is also becoming widespread in sports facilities today because it permits the creation of lightweight roof and facade structures where daylight is used effectively. ETFE is a plastic material with high chemical and mechanical resistance over a wide temperature range. Used in thin layers, the material is employed in the form of pneumatic (inflatable) membranes or envelopes, worked with their shapes like these types of plastics [16]. While the light transmittance of normal glass is around 80%, the light transmittance of ETFE films exceeds 90% [2]. Advantages such as light transmittance, durability, robustness, the non-stick property of its surface allowing it to self-clean with rain, and resistance to fading under UV light or atmospheric pollution – thus requiring no maintenance – make the material's sustainable use in roofs and facades possible. Significant examples of sports facilities using ETFE in the building envelope are listed in Table 3, ranked by the area of ETFE surface used. In recently completed and ongoing examples, it has been observed that the 'sustainability qualities' identified in the study are increasingly being used together. Associate Prof. Ahmet Vefa Orhon / Dokuz Eylül University - Faculty of Architecture Associate Prof. Müjde Altın / Dokuz Eylül University - Faculty of Architecture

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Note: This study was prepared by developing the paper titled "Sustainable Roofs and Facades in Sports Facilities" presented at the 7th Roof and Facade Symposium held at YTU, Istanbul on 5-6 April 2014.