Singapore has long been known to be a city of ‘green’ – when the term was still seen as revolutionary and unique, Singapore’s Government pursued the vision, believing it “would mitigate against the harsh urban environment as Singapore developed (and) improve the quality of life for Singaporeans.” The Gardens by the Bay precinct was born from this vision, pushing Singapore to become a City in a Garden, rather than a Garden City. In 2006 an international design competition was run by National Parks Singapore with the aim of finding an innovative master plan that would contribute to the redevelopment of the Marina Bay area and become an eco-tourist destination, showcasing sustainable practices and plants from across the globe. A team led by Andrew Grant of Grant Associates, involving Wilkinson Eyre Architects and Atelier Ten as environmental designers and building services engineers, won the competition. Opened in its entirety in 2012, the site comprises of 52 hectares of landscaped gardens, highlighting the ethnic makeup of Singapore, as well as a 20,000 square-metre complex of cooled conservatories and 18 enormous structures, known as Supertrees, supporting vertical gardens and the energy production and ventilation systems associated with the complex. As one visitor to the site commented; The cocktail of architecture, engineering and turbo charged nature presents an extraordinary vision, something surprising, surreal and, on occasion, truly breathtaking. It is strikingly original in its strangeness yet it also creates a landscape which builds on familiar precedents. Primarily concerned with recreating nature, the site has been developed as an advanced ecosystem, offering visitors an insight into a compacted environment they may never get to experience anywhere else, especially in the face of climate change. Furthermore, the project demonstrates how design optimisation and cross-discipline integration can result in environmentally responsive buildings even in very demanding climatic conditions. Marked as the fourth most popular tourist destination in the world, Gardens by the Bay serves as a green lungs in an urban jungle, successfully rekindling “human instincts about the beauty and wonder of nature.”
The conservatory complex consists of two large biomes, strategically designed to contrast interior environments and visitor experiences. Located on the waters edge to ensure maximum sun exposure and minimal interference from future development, the larger dome and been dubbed the ‘Flower Dome’, while the taller of the two is known as the ‘Cloud Forest’. The Flower Dome structure contains the cool, dry climate of the Mediterranean, exhibiting a range of colourful flowers and plants that would otherwise not be seen in the tropical climate of Singapore. Housing a number of function spaces and restaurants, the interior design draws on the Mediterranean landscape – dry hillsides, rocky terraces, stony outcrops – each highlighting the affiliation between land, geology, vegetation and cultivation. The Cloud Forest on the other hand is an immersive vertical journey through a bio diverse, tropical green forest that even includes an artificial mountain. More focused on the educational aspect of the entire precinct, the Cloud Forest integrates multi-media interpretation to emphasise the relationship between plants and the planet, and how the warming of tropical landscapes is threatening biodiversity. Internally, the biomes are worlds apart, but on the exterior both are contained within a grid shell, as light as possible and stiffened by a series of ribs that stabilise the grid. The grid shell supports large double-glazed units, the key to the environmental modulation of the buildings and falling in line with the team’s intent to achieve as much environmental control via passive measures. Prior to the project NParks constructed 6 prototype glasshouses to determine the ideal conditions for plants to thrive in various environmental conditions. The results were applied to both biomes facades, implementing double glazed units that allow for approximately 65% of the incident daylight to pass through, with only 35% of the solar heat. Additional low e-coating on the glazing acts as an infrared light reflector, distributing unwanted heat from daylight spectrum. Further to this, an external shading system has been developed to modulate internal daylight levels. Each shade can be individually activated to provide patches of shade for visitors, and as a collective provides additional resilience to sun exposure in case of a cooling system failure. Both elements work in tandem to provide comfort for visitors, reduced need for energy consuming cooling mechanisms, reduced solar thermal heat transmission and optimal environments for the plants.
Even with the use of high performance glass and external shading, the interior of both biomes needed additional cooling to ensure human thermal comfort. Four methods of cooling were decided upon after careful research throughout the early conceptual stages through to construction. The four methods include:
- Displacement ventilation air conditioning: Introducing the conditioning air at low level within the occupied zone to limit the volume of the building that requires conditioning, thereby reducing plant capacities and energy use.
- Radiant Cooling: Integrated into pathways and pavements within the biomes to absorb and remove incident absorbed radiation. Reduces the amount of heat gain to be dealt with by the air systems and reduces mean radiant temperature for occupants.
- Desiccant dehumidification: Removes the need for refrigeration based dehumidification of air. The desiccant regeneration process allows waste heat to be used as a regeneration energy source.
- Direct evaporative humidification: Used within the cloud forest dome to provide the very high humidity levels required and enhance cooling performance.
The main mode of cooling for both biomes is displacement ventilation, supplying air from diffusers integrated into the vertical surfaces of the planter beds and through displacement diffuser terminals positioned throughout the structure. The system uses dehumidified fresh and recirculated air supplied from units located in plant rooms below the surface, as well as fresh air drawn in from the outside. The mountain within the Cloud Forest is in fact a giant air displacement unit – cold air spills out of the holes and disperses down the mountain, in conjunction with fogger sprays, keeping both the plants and people efficiently cool. Beyond maintaining comfort, the displacement ventilation system in conjunction with chilled water supplies also alters the interior temperature of the biomes at different times of the day and during the year to replicate conditions in the wild and stimulate plant development and flowering.
Committed to applying intelligent and integrated building responses, the team behind Gardens by the Bay developed a system that utilises biomass as the primary source of energy for cooling the biomes. Using up to 70tons of tree cuttings from the streets of Singapore, the biomass boiler is part of a system that powers absorption chillers that convert the generated heat into chilled water. The chilled water is fed to the conservatories for use in cooling the fabric, lowering the temperature of all concrete paths and subsequently lowering visitors perceived body temperature. The power generated is used to run the conventional chillers in the plant room, a place where fresh air is drawn in and dried with desiccant prior to passing through the chillers for delivery onto the planted displays. Whilst the desiccant reduces the amount of energy required to cool the air, it itself becomes saturated with extracted moisture. In response, hot air collected from the top of the glasshouses (where the air is at its highest temperature), is used to regenerate the desiccant by driving off the moisture, and ultimately increasing the efficiency of the system. Although technically challenging, the end result of implementing such a system has resulted in a zero carbon conditioning system for both glasshouses. The other defining feature of the Gardens by the Bay precinct is the enormous and iconic Supertrees. Between 25 and 50 metres in height, the vertical gardens number 18 in total – two clusters of three trees and one cluster of twelve trees. Constructed of concrete and steel, each Supertree has a hollow core surrounded by a diaphanous steel cladding to which the vertical garden attaches. At the top of several Supertrees are evacuated tube solar collectors and when heated accordingly can partially drive the desiccant regeneration process. In addition to solar collectors, photovoltaic panels have also been strategically placed on the heads of the Supertrees to further offset the site’s carbon emissions and provide solar energy sources. Maximising space, the hollow cores of specific Supertrees have been utilised for various purposes including; a chimney for the biomass boiler, a storage facility for the discharges from the regeneration unit of the liquid desiccant dehumidification system and as a vent for the hot moist air generated from the dehumidification process. Lastly, the Supertrees provide abundant shade for visitors roaming the gardens, as well as spanning views of the precinct, aerial walking platforms and rooftop bars and restaurants. The seamless integration of visual masterpiece, functional structures for both sustainable energy and water technologies and leisure space for engagement with the natural environment, makes the Supertrees an iconic landmark for Singapore, and an integral element of the precinct as a whole.
Gardens by the Bay has won 16 awards since it’s opening in 2012, including the Landscape Institute Award, Design for Asia and the RIBA Lubetkin. It stands as a beacon for the application of sustainable design in the Southeast Asia region, emphasising the fact that with research, innovation and cross-discipline partnerships, highly complex processes and systems can evolve to meet environmental and climatic demands, without the sacrifice of visual appeal or modernist design. The large scale sustainable cooling techniques implemented open the door for future opportunities of application in high density urban centres, supporting the idea that development can be sustainable, structures can be symbiotic and comfort can remain at the forefront of tropical design but not necessarily produce environmental degradation. Igniting people’s interest in the natural world and raising awareness of the benefits of greenery, was always at the forefront of the precinct’s master plan. As Andrew Grant commented “in order for people living in cities to have a holistic and well adjusted quality of life, they must have meaningful physical and emotional encounters with nature… however successful we are at sorting out the mechanics of sustainability through innovative technologies and systems, it will be worthless if all it does is create a banal, sterile world. Thus, Gardens by the Bay is more than just a technological masterpiece, it is a means to encourage relationships with natural landscapes, to promote social and environmental sustainability and uncover the potential ways cities can maintain greenery and respond to climate change.