Architects and engineers in temperate regions have thought of many ways of designing low-energy buildings. Trouble is, they don’t work in an equatorial climate, and nobody has come up with any alternatives – until Singapore asked Ken Yeang to design a library …
The next time the G8 leaders discuss carbon emissions and climate change, they should do it in Singapore. The temperature here is a sweltering 31°C in the day and a sticky 24°C at night, all year round. And if the politicians don’t succeed in curbing emissions, then building designers might want to come here to learn a little about how to deal with the consequences of that failure.
The star architectural attraction of the island is the New National Library Board Building. This project was intended to show how a low-energy building could be built in an equatorial climate, and it seems to have succeeded: it is the first building to win the Singaporean government’s Green Mark platinum award, which makes it the most sustainable building on the island.
The Green Mark, which was introduced at the beginning of this year, is an indication that Singapore, that most planned of societies, has started thinking about how it will cope with a century in which energy prices and temperatures both rise to uncomfortable levels. The mark is similar to our own BREEAM and takes into account energy efficiency, water consumption and environmental innovation.
The library was designed by architect Ken Yeang’s practice, Hamzah & Yeang. Yeang, who has become famous in Europe for his green towers, is passionate about environment-friendly buildings – and as he has just joined UK firm Llewelyn Davies, we are likely to see more of his ideas popping up over here.
But Yeang’s library is much more than just a green building – and more than just a library. It also houses noisy multimedia facilities, as well as an auditorium and exhibition space in a small, curved block. A second, larger rectangular block contains the more traditional library collections. An internal street open to the elements fills the gap between the two blocks – bridges are used to link these at the upper levels. Underneath the library block is a large plaza with a cafe. “We wanted to make it a cultural building,” says Yeang. “It’s people that make the culture so we created this cultural plaza.”
Low-energy principles that have become standard in Britain do not work in Singapore. “If you take the external temperature and humidity and compare that to a chart showing comfortable temperatures and humidity levels, you will find 100% of people will be dissatisfied every day of the year,” says Russell Cole, an assistant director at Arup, who was responsible for the facade engineering. This means natural ventilation will not work – it is always too hot to cool down the building’s structure using cool night air. The only area where natural ventilation is used is the plaza. The space between the two blocks creates a stack effect that pulls the air from outside and through the plaza. “When you get moving air you get a cooling effect even in areas of high humidity,” says Cole. The internal areas are all fully air-conditioned 24 hours a day for comfort, and to keep the books in good condition.
The strategy is to prevent direct sunlight entering the building, thereby minimising the need for mechanical cooling. “The form of the building took into consideration the orientation of the sun,” says Rajiv Ratnarajah, Hamzah & Yeang’s project architect. “We wanted to block out the hot, western evening sun, so the solid cores face west and alternating terraces protect that corner of the building.”
However it was important to get as much useful daylight into the building as possible to cut down the need for artificial light. The answer is what are probably some of the biggest sunshades to have been fitted on a curtain wall. These wrap around the library, shading both blocks and the internal street, and are up to 6 m wide in places. “We didn’t want any reflective tint whatsoever on the glass, so the only way we could do this was to have these huge overhangs,” says Ratnarajah. “The aesthetic of the building derives from the careful planning of the daylighting, sun angles and terraces and the position and size of the sunshades.”
Getting the sunshades to bridge the two blocks was challenging, as they move independently of each other. These shades are 6 m wide and 24 m long, yet are only 400 mm deep as they form a continuum with the smaller shades attached to the blocks. The shades have an internal frame covered with aluminium sheets and each level of the shades is linked together using an arrangement of cables and columns similar to those used to link the wings of a triplane. This is attached to each block using special bearings that accommodate any movement.
Plain double-glazing, coated to cut down glare and heat gain from solar radiation, completes the facade. Some areas of the building have automated drop-down blinds to cope with the 2% of the year when the sun is too low for the sunshades to be effective, and lights are automatically turned off when daylight levels are high.
The building has two huge gardens that contain 12 m high trees at the 5th and 10th floor levels. “The planting increases biodiversity and also helps retain water on the site,” says Yeang. It also provides a pleasant outdoor space and an attractive view for the library users.
The library has also been designed to minimise the energy embodied in its construction materials. Recycled and recyclable flooring and wall finishes have been used and the timber comes from sustainable sources. Because natural ventilation doesn’t work there is no advantage in having a concrete frame to act as a thermal heat sink. Steel was selected for the frame as it contains less embodied energy than concrete and is 100% recyclable.
Because the library was constructed using a design-and-build contract, some aspirations have been watered down. The final structure is a concrete-encased steel frame – this saved money on fireproofing. Ratnarajah says sustainable building design and construction is still a novel concept in Singapore. “The mindset isn’t there yet,” he says. “When we come up with a green specification most contractors don’t understand it, so you have to explain everything to them.”
Ratnarajah, it seems, faces hurdles similar to the more enlightened members of the G8 countries. “The question is whether the construction industry is willing to meet these standards, as Singapore has the infrastructure in place,” he explains. “It’s now a matter of persuading the construction industry this is the way to go.” Does that sound familiar?
client National Library Board architect Hamzah & Yeang
structural and services engineer Buro Happold facade engineering Arup
embodied energy of materials Battle McCarthy and BRE cladding Permasteelisa contractor Nishimatsu Construction Co and Lum Chang Building Contractors
New National Library key points
- Library in Singapore designed by architect Ken Yeang’s firm Hamzah & Yeang
- First new building in Singapore to win the top rating in the city state’s green awards
- A fully air-conditioned green building – natural ventilation doesn’t work in a tropical climate
- Key challenge to maximise natural lighting but minimise solar gain
- Energy consumption minimised by using extensive sunshading
- Building environmental impact minimised by careful material selection
16 storeys high, with three levels of basements
Total gross area (excluding parking): 59,030 m2
Total net area: 30,797 m2
Green space: 6300 m2
Embodied energy (calculated)
Typical office building: 10-18 GJ/m2
New National Library: 17 GJ/m2
Note: The specifications for a library are generally of a higher standard than office buildings. No figures exist for a typical library.
Energy consumption (calculated)
Typical Singapore commercial office building: 230 kWh/m2/annum
New National Library: 185 kWh/m2/annum
General library areas: 150 W/m2
Archival areas (book stacks): 10 W/m2
New National Library offices: 20 W/m2
Annual wind speed average (calculated)
Public plaza: 0.814 m/s
Sky gardens: 0.532 m/s