Tackling urban heat with smarter design

By Alistair Jones

SMU Office of Research & Tech Transfer – It’s known as the Urban Heat Island effect, the way big cities experience hotter outdoor temperatures than nearby rural areas.

Cars and concrete canyons are obvious culprits, but other factors are more complex and the effect is exacerbated by a warming global climate. Implications for public health and sustainable prosperity are considerable.

Singapore is particularly vulnerable. As a metropolis on a low-lying island near the equator, with few cooling breezes, year-round high temperatures and daunting humidity, outdoor conditions are often sweltering and likely to become more so. Already the retail heart of Orchard Road can be 7 degrees Celsius hotter than the farmland of Lim Chu Kang.

Enter the Cooling Singapore (CS) project, a research initiative funded by the National Research Foundation, bringing together a multi-disciplinary team of experts to assess and measure cooling strategies, develop a decision support system and design climate-responsive guidelines.

The study launched in 2017 as CS 1.0, which identified possible mitigating strategies from existing research along with knowledge and technology gaps to guide future R&D activities. Next came CS 1.5, which has just concluded with the collection of practical data from case studies, on-site measurements, technical reports and community feedback.

“[With CS 1.5] we broadened our understanding in terms of looking at how heat is not just an urban or a building problem, or a traffic problem, but also a people problem – how an individual responds to exposure to warmer conditions in the city,” explains Winston Chow, an Associate Professor of Science, Technology and Society at Singapore Management University (SMU) and one of the Co-Principal Investigators on the CS project.

The researchers will soon create a computer-based Digital Urban Climate Twin (DUCT) – a virtual simulation of Singapore that will assist government and planners in considering a development site and generate scenarios to predict the impact of design options, informed by a detailed analysis of factors affecting outdoor thermal comfort.

“I wouldn't just call it a tool kit,” says Professor Chow. “It's [more] an approach to help with smart climate design possibilities. We see this sort of approach as potentially useful for other rapidly developing cities in Southeast Asia.”

All interconnected

In the past, planners in Singapore have had difficulty considering the climatic aspects and implications of their decisions.

“Urban planners tend to focus on their area of interest, their particular spatial skill or within a certain boundary. But urban climate change goes beyond a certain neighbourhood,” Professor Chow says.

“Let’s say that there’s a new parcel of land available for residential development. People may say, 'Hey, it's an exciting greenfield site, let's make it into an eco-town, or an eco-friendly neighbourhood with park connectors, with shaded spaces, green spaces everywhere and roof-top gardens, all of which is a great thing,” he notes. 

“But that existing green space has a cooling effect on the surrounding neighbourhoods. So what would be the influence of removing this green space on these other areas as well?

“The concern is that if urban planning is too segmented and just focuses on one precinct you might miss the bigger picture in terms of overall sustainability across spatial scales.”

Professor Chow concedes that planners are following their remit in concentrating on a specific location.

“It's a great thing that precinct design is so small-scale and focused, but we're just saying there might be other larger-scale issues you want to consider. Our project has architects, building design people, engineers, urban scientists, climatologists, mechanical engineers, environmental engineers and so forth. We approach it as a multi-discipline problem.”

No one size fits all

While it may seem that the more trees you plant the better things will be, the study has turned up a surprising finding.

“If you make things too green, you get a humidity problem because comfort for an individual is not just how hot it is, it's also how humid you are. If you make it too humid, people will complain, particularly with Singapore's low wind speeds.

“There's a fine balance between finding out what sort of trees you're going to put in, how many and their profile, so that it won't make it too uncomfortable, even though you reduce temperatures,” Professor Chow observes.

“Vegetation is not homogenous. You can have tall trees that have huge amounts of shade at high levels but with empty space at the bottom; that is great for certain places. But then with most of the trees you can also have shrubs at the side which protect from the radiation from the road.

“And you can orientate the buildings in a way that maximises the very small-scale wind flow. Marina Bay’s one example. So whatever small sea breeze comes from the coast, together with the monsoons, the buildings are orientated to allow breezes to make it cool for pedestrians and will also flush out air pollution.

“The point is that there is no one size fits all solutions, it depends on the urban context,” Professor Chow says.

Something tangible

The business community has been reaching out to the CS project for ideas – from power companies, to firms interested in more efficient air-conditioning, to landscape architects who know that certain vegetation improves micro-climate conditions for a private house.

“It's not from the goodness of their hearts or corporate social responsibility, but because it makes sense [and also] they know there's money to be made in urban sustainability,” notes Professor Chow.

The CS public campaigns have revealed an “overwhelming willingness” among Singaporeans to do what they can to help mitigate the city's rising heat.

“The general worry is that this is a big problem, it's going to get worse, and is there something we can do about it,” Professor Chow explains. “Singapore could get to the point where it's too bloody hot to do anything.”

Public awareness and discussion was boosted by Prime Minister Lee Hsien Loong at the 2019 National Day Rally, where he affirmed that climate change is one of the gravest challenges the human race faces and Singapore is already feeling its impact.

“So let's translate the concern into something tangible, and the CS project is on the way to trying to help stakeholders, such as the government and the private sector, figure what's the best course of action,” says Professor Chow.  

“[And] it's one thing to have the nice computer [model] that has the attractive inputs and the very sexy outputs, but let's not forget that there are discernible, viewable impacts to people, to animals and to vegetation within Singapore,” he adds.

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