Architects: Wilkinson Eyre Architects
Location: Marina Bay, Singapore, Republic of Singapore
The Singapore Gardens are located in Marina Bay, Gardens by the Bay is a key project in delivering the Singapore Government’s vision of transforming Singapore into a ‘City in a Garden’. At a total of 101 hectares, the Gardens by the Bay project comprises three distinct waterfront gardens – Bay South, Bay East and Bay Central. The commission to design the 54 hectare Bay South garden was won in 2006 by a team led by Grant Associates and including Wilkinson Eyre Architects, Atelier One, Atelier Ten, Land Design and Davis Langdon and Seah.
At the heart of Bay South Garden is the Cooled Conservatory Complex which is the focal point of the Gardens. The two main Conservatories cover an area in excess of 20,000sq m and are among the largest climate-controlled glasshouses in the world. They provide a spectacular, all-weather attraction and comprise a 1.28 hectare cool dry conservatory (the ‘Flower Dome’) and a 0.73 hectare cool moist conservatory (the ‘Cloud Forest’). Each has its own distinct character, but both explore the horticulture of those environments most likely to be affected by climate change.
The Flower Dome tells the story of plants and people in the Mediterranean climate zone, and how the plants cultivated in these regions will gradually become endangered as temperatures rise. It has a planted footprint of more than 10,100 sq m and aims to bring alive the experience of seasonal change for visitors more used to Singapore’s eternally tropical climate and lush green vegetation. From the lavender fields and olive groves of the Cultivated Worlds section to the baobab and pachypodium trees in the Strange Worlds area, the visitor is presented with a unique collection of plants. The landform of the conservatories draws inspiration from Mediterranean landscapes and evokes the language of dry, sun-baked hillsides punctuated with rocky terraces and stony outcrops, and the intimate bond between land, geology, vegetation and cultivation. At the centre of this permanent display is the Flower Field – a vast carpet of flowers in bloom which will change seasonally.
The Cloud Forest highlights the relationship between plants and the planet, showing how the warming of the cool tropical cloud forests will threaten biodiversity. With a smaller footprint but greater height than Flower Dome, it has at its heart a planted ‘Mountain’ from which a 35m high waterfall drops. Visitors can experience the forest at different levels from a Cloud Walk, a Canopy Walk and the Forest Floor and Ravine Walks. Within the mountain, a series of exhibition spaces describe the impact of incremental temperature change and the sustainable technologies employed across the gardens, while at its foot is the Ravine – a series of darkened secret gardens surrounded in mist.
Both conservatories have a dual system structure of gridshell and arches to permit as much light as possible through to the planted displays within. The gridshell portion is very fragile (like an egg) and is designed to only support its own weight and the weight of the glass. Wind loads are resisted by the arches that are set away from the surface of the envelope and arranged radially in line with the geometry of the gridshell. This structural combination creates a distinctive, lightweight clear-span structure which, in the shallower slope of the Flower Dome, is thought to be among the largest gridshells in the world.
To maximise the daylight entering the conservatories, the gridshell is constructed from manufactured steel members that are triangular in section. These standard members are linked at plate steel nodes, designed in standardised ‘families’ to lower manufacturing cost whilst efficiently accommodating the changing geometry of the building. The ribs, which are anchored into concrete ‘shoes’ at ground level, are painted off-white to reflect light and heat, their sections tapering along their length in relation to the loads placed upon them.
Bay South Garden is built on reclaimed land, a low lying, flat area on the shore of Marina Bay. In the absence of a natural landscape the conservatories are envisaged as landforms, a pair of artificial landmarks that prominently address the bay and the skyscrapers of dense urban districts around it.
A tiered approach has been taken to the energy design of the Cooled Conservatories with as much environmental control achieved through passive means as possible before resorting to highly efficient, active systems. The principal design challenge of the Cooled Conservatories is the conflicting need to maintain the high light levels required by the plants whilst minimising the associated solar heat gain.
The form of the biomes is optimised structurally (as described above) but also works well environmentally by containing a large volume within a relatively small surface area. In addition to form of the Flower Dome is tilted forward so that it leans over towards the Marina Bay; the north façade is therefore self-shaded and never receives the full glare of the sun.
The envelope is critical to the success of the system: the structure has been designed to cast as little shadow as possible whilst highly selective glass is used to filter out as much heat as possible. Thanks to a low-e coating (on face#2), the glass has a high visible light transmission (VLT) coupled with a low solar heat gain coefficient (SHGC). In practice this means approximately 64% of the available light is transmitted into the building with only 38% of the corresponding heat gain. Singapore is often overcast but even a cloudy sky transmits enough light for the exhibited flowers to bloom. When the sun does come out, deployable shades are used to control the light levels and limit the heat gain. These automated fabric shades are concealed within the arches so as to not cast any extra shadow when not in use.
Inside cool air is delivered at low velocity, trickling in and between the planted displays. This collects in pockets of the shaped internal landscape, providing comfort to the visitors and – most importantly – the right growing conditions for the plants. Only these lower, inhabited levels are cooled. In the space above the planting and people the air is allowed to stratify according to temperature and a reservoir of hot air collects at the top of the dome.
Fresh air is drawn into the plant rooms and dried with a dessicant prior to passing through conventional chillers. The dessicant reduces the amount of energy required to cool the air but itself becomes saturated with extracted moisture. The hot air collected from the top of the glasshouses (along with surplus heat from the on-site biomass boiler) is used to regenerate the dessicant by driving off the moisture. The biomass boiler is fuelled entirely with green waste collected from around the city’s national parks and creates sufficient energy to cool the conservatories.
The conservatories were conceived as an integral part of a wider garden ecosystem in which the main structures and planting work together in tandem, simulating nature at work and minimising the environmental impact of the overall development.