With Summer rolling around, it’s time to drag out the fans, wet towels, and baggy shorts! But keeping cool isn’t just a problem for people – it’s an even bigger problem for our cities.

Cities are affected by what are called Urban Heat Islands. Urban areas are made of materials like concrete and steel, which retains heat and prevents water circulation. As a result, the ambient temperature rises, up to 7°C warmer!

There is hope though. Science as given us some very futuristic ways to cooling our cities down. Below are a list of 5 of those ways, all currently being used by various local councils and developers.

We’ve got another article on how to stay personally cool in summer – we’d love you to check it out!

Why should we cool down our cities?

There are lots of reasons to try and ease the effect of urban heat islands. For one, heat is a real health risk, from sunburn to heat stroke. Climate Change has already increased global temperatures, and an extra 7°C in our cities only makes things worse.

Urban heat islands also affect local geography. Heat islands can change rainfall patterns and local growing seasons. They also decrease air quality through higher production of pollutants like ozone, and decrease water quality by heating up local waterways.

Of course, there are real perks of reversing the urban heat effect. Reducing the temperature of our cities by a few degrees will make them more livable. People are more productive and tend to shop more when they’re not too hot, both of which are good for local economies.


5 ways to reduce the Urban Heat Island effect

Reducing the impact of heat islands is both possible and desirable.

Here are the best ways to keep our cities cool, from the super simple to the super smart.

1. Plant more Trees

One of the best ways to tackle the problem of the urban heat island is simple – plant more trees. Evapotranspiration might sound made up, but it’s a real process that helps cool our cities down. Trees soak up radiation from the sun before it hits the ground, and the heat evaporates the water from the tree’s leaves. That cools the surrounding area.

How much of an impact can this make? A 4 meter high Callery pear tree can provide around 6kW of cooling – around the same as two small air conditioners! There is a catch though. The trees need to be in good health. After all, there needs to be plenty of water in the leaves to be evaporated.

There’s another benefit to planting trees where they cast shade on a building, especially to the east of west. Studies have found this kind of shading can reducing household air conditioning by 20% to 30%. So, money really does grow on trees…

How do we plant more trees? Councils and property developers are largely responsible for that. Central Park in Sydney was designed with hanging gardens, which uses vertical space to increase city greenery. Meanwhile, councils across the country are committing to increasing green space in their city plans.

Central Park in Sydney

2. Reduce reflective surfaces

Here’s a little science hit: Albedo measures how much heat is retained or reflected by a surface. Surfaces with high albedo reflect more heat, so they stay cool.

The problem is we build cities from materials with low albedo, like concrete, steel, and bitumen. But it doesn’t have to stay that way.

Councils and cities around the world are now encouraging the use of more reflective surfaces. Parramatta is one of those cities, where council promotes the use of lighter coloured materials, which reflect more heat.

New technologies like cool pavement are also helping to spread this approach even further.

A skyscraper with reflective surfaces, which reduces urban heat island effect thanks to the albedo effects

3. Cut back on parking

One of the worst offenders when it comes to causing large swathes of high heat absorbing material are car parks. Just check out this satellite image of Dodgers Stadium in Los Angeles.

An aerial shot of Dodgers Stadium in Los Angeles. the amount of parking is remarkable, taking up well over ten times the space as the stadium, which adds to the urban heat island effect.

We can stop our car parks contributing to the urban heat island problem by building them from cool pavement, or by hanging a light coloured shade cloth over them.

But why not reduce the need for parking all together?

Technologies like car share, along with public transport and ride share, make it easy to live without owning a car. With less cars we won’t need as much parking, whether we’re watching baseball or buying groceries.

Eventually, less cars will mean we can convert roads into more footpaths and green space. Reservoir Street in Sydney’s Surry Hills is a great example of this. Thanks to GoGet reducing the need for parking, Sydney City Council was able to convert an entire lane of parking into green space!

A before and after view of Resevoir Street in Surry Hills, Sydney. Thanks to GoGet car share reducing the need for parking, council was able to turn an entire lane of parking into green space

4. Build smart buildings

There are some new heat-reducing technologies at work in buildings across our cities, and some of them are very cool – figuratively and literally!

One example of a small development built with this in mind is The Commons, in Melbourne’s Brunswick. Home to both apartments and a co-working space, The Commons combines a lot of the elements mentioned above, with lots of greenery, reflective surfaces, and a green roof. It also has no parking space included with its apartments – except for a GoGet spot!

To learn more about The Commons project, watch this video, then watch this one.

The roof of The Commons in Brunswick Melbourne, which is an example of a smart building using science to help reduce the urban heat island effect

On a larger scale, the Sony City Osaki Building in Tokyo has a technology called BioSkin that reduces the heat island effect. The building collects water on the roof, then feeds it through ceramic channels on the building’s facade. The water evaporates through the ceramic, emulating the evapotranspiration effect of trees. BioSkin’s developers claim it cools the surrounding air by 2°C, and the building surface by 12°C!

This video is a little dry, but gives you heaps of information on BioSkin from one of its designers. Tomohiko Yamanashi starts speaking about BioSkin at around the 5’30’’ mark.

5. Take better measurements

The previous methods to cool our cities have been fairly simple. However, there are some very futuristic ways the heat of our cities is being managed, thanks to the Internet of Things.

The Internet of Things consists of very small computers connected to the internet, able to make measurements and perform tasks remotely and autonomously. GoGet card readers are a basic example of an IoT technology.

An illustration of the internet of things, and the sort of things that connect to each other through the cloud, from cities to people, wifi to home speakers.

For urban heat islands, IoT heat sensors could be a game changer. We can now affordably install thousands of IoT thermometers on buildings, in trees, on roads, and in cars and buses, to make a living, breathing map of the city’s temperature.

That will help identify where there are heat spikes, and measure the effectiveness of attempts to cool things down. Remote measurement could also trigger responses to sudden heat spikes, by automatically spraying water onto a surface, for example.

They say what gets measured gets managed. Thanks to these massive improvements in how we measure our cities, we’ll be much more effective managers very soon.

Hot in the city? Not for long

As the world gets more urbanised, improvements in the way we run our cities will become even more important. Cooling down urban heat islands is just one part of that, but it’s a problem we’re already working on.

So what can you do as an individual? The best way to make a difference yourself is to get interested in cities! If you see a cool project, tell your friends about it. Then, get engaged with your local council on the work it’s doing to future-proof your neighbourhood.

If your heating problem is a little more local – you might be interested in our article on how to stay cool in summer, cheaply and sustainably.

About Tim Beau Bennett

Tim is GoGet's primary wordsmith. He's an ex-journalist who has written on technology and cities for large and small companies, as well as for news publications including ABC online.