Beat the Urban Heat

As the mercury is set to hit whopping 30˚C on this mid-May day it feels like it might be the right time to talk about urban heat.

Have you ever been walking through a park on a warm day enjoying the cool shade then stepped out into a streetscape filled with tall buildings and felt a distinct rise in temperature? If you have, you’ve experienced first hand what climate scientists have termed the ‘urban heat island’ effect.

Heavily urbanised areas within cities are on average 1℃ – 3℃ hotter than other areas, and can even reach up to 10℃ hotter.

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Image showing the various temperatures in an urban environment

Why does it happen?

The consequence of high populations within cities is higher urban density; we build taller buildings closer together to accommodate large amounts of people in a small area. We replace vegetated areas with buildings and streets that are constructed with dark materials that retain heat like asphalt and concrete.

On a warm day the sun heats the dry and exposed urban surfaces to well above air temperatures – natural cooling processes like evaporation from moist soils or cool breezes are blocked by our infrastructure – the result is urban heat islands. And it doesn’t stop when the sun goes down! The effect lingers into the night as building materials radiate stored heat.

On top of that dense urban areas also generate a lot more heat through ‘waste heat‘. People and their machines – cars, lawn mowers, air-conditioners, fridges etc. – are always burning off energy as heat. Unfortunately, because of the dense urban environment the heat has no way of escaping so it lingers between buildings contributing to the urban heat island.

What’s the problem?

The flow-on effects of urban heat are significant. The perfect storm of global warming, the urban heat island effect, and a poorly timed heat wave can pose a serious health risk – people are more frequently being hospitalised or even killed as a result of heat related stress. Not to mention soaring energy costs associated with the installation and operation of air-conditioning (which in a cruel twist adds to the urban heat effect).

What’s the solution?

There are changes that we can make in the way we plan and develop our cities that can have enormous impacts. Simply, it’s building with lighter more reflective materials and more considered urban planning that calls for more parks, natural spaces and trees.

Trees provide a range of social, environmental and economic benefits that increase the quality of urban life – but most importantly they provide shade and help filter the air to reduce the urban heat island effect.

And it’s not that difficult to incorporate them into our urban streetscapes. Check out how the City of Melbourne took the opportunity to combine tree planting with a new bicycle lane in La Trobe Street.

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La Trobe Street bicycle path.

Some local governments have strategies in place to conserve established trees and encourage the planting of new trees. The City of Perth has an Urban Forest Plan that is focused on promoting the long-term health and resilience of trees in the urban environment.

We are very fortunate here at Urbaqua to have some beautiful trees outside our office in Leederville that do a great job of keeping the street nice and cool.

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From everyone at Urbaqua have a great weekend!

Sources:

https://theconversation.com/making-cities-cooler-is-a-no-brainer-so-why-are-we-doing-so-little-about-it-95607

http://www.growinggreenguide.org/technical-guide/introduction-to-roofs-walls-and-facades/green-roof-definition/

https://www.telegraph.co.uk/news/2017/08/05/european-heatwave-kills-five-temperatures-soar-40c/

https://theconversation.com/we-calculated-how-much-money-trees-save-for-your-city-95198

https://www.epa.gov/heat-islands/learn-about-heat-islands

https://www.nationalgeographic.org/encyclopedia/urban-heat-island/

https://www.perth.wa.gov.au/planning-development/city-initiatives/urban-forest-plan

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