Urban Heat Island

Tonight, in a lecture on Urban Microclimate, Jonathan Fox expressed the concept of Urban Heat Island to us as an equation. In his explanation, Jonathan put forth the very interesting suggestion of a relationship between Urban Heat Island and the ageing population. Whilst my mind immediately made the link that significant climatic differentiation in urban areas was particularly dangerous for the elderly who are particularly susceptible to the heat, Jonathan went on to explain that the elderly, being more highly affected by the heat, are more reliant on mechanical heating and cooling and thus likely contributing to the heat island effect even more.

The contribution of mechanical heating and cooling to the urban heat island was illustrated in a graph which highlighted HVAC use as the perpetrator of 40% of our total energy usage.

The close but not identical nature of my first thought as compared to Jonathan’s explanation got me thinking further. Urban Heat Island is not an equation. It is a cycle. This means that the tools we use to mitigate the symptoms** of Urban Heat Island in fact contribute to and worsen the problem. This is not good. As our surroundings get hotter, more stuffy and more polluted, we rely on air conditioning more and more to improve the temperature, flow and quality of the air inside our buildings. Unfortunately, air-conditioning units emit CO2 and heat to the air immediately outside our buildings, increasing our reliance upon them. Hot and dirty city air not only makes us uncomfortable, it makes us sick. Obviously the best defence against urban heat island is the incorporation of green surfaces in our cities.

Chua, G & Hadley, E 2014, 'Sydney tower named world's 'Best Tall Building' by CTBUH', Architecture & Design, November 2014, accessed 2 May 2016, <http://www.architectureanddesign.com.au/news/one-central-park-sydney-named-the-world-s-best-tal>.

Hopefully this is just the beginning and we see our buildings start to move from the now very overused and rarely accurate term ‘green’ to a more literal interpretation, physically covered in greenery. Unfortunately, introducing greenery can only come slowly and it has limitations. More immediately, we need to stop the everyday air-conditioner. There are so many alternatives out there now. Evaporative cooling, trigeneration, chilled beams. Many examples of passive thermal design in which no active cooling system is required at all sans for maybe a simple fan.

Unfortunately HVAC is not our only heat source in the city. And a big one is producing even more heat and pollution and odorous fumes. I’m sure we’ve all had the experience of jumping out of plane in a foreign city to be overwhelmed (and sickened) by the city smell. Despite travelling to some pretty dense parts of Asia, I remember this most vividly upon arrival in Los Angeles - one of the most car-dependent cities in the world. The fumes and heat generated by all that traffic was unbearable.

Groves, M 2013 'Elon Musk hates 405 Freeway traffic, offers money to speed widening', Los Angeles Times, 25 April 2013, accessed 2 May 2016, <http://articles.latimes.com/2013/apr/25/local/la-me-ln-elon-musk-405-freeway-20130425>.

Interestingly enough, the 2013 article written by Martha Groves from which this image was grabbed discusses the need for further road-widening due to major traffic problems in LA. Unfortunately it seems LA is stuck in its own cycle - it has been developed so entirely around cars that residents rely totally on cars and thus, road infrastructure needs to further developed, further cutting out the place for public transport within their system.

Phasing out cars from our cities would be hugely beneficial to mitigating the urban heat island due to its triple-fold outcome. Firstly, in that the impact of a significant generator of heat, air pollutants and greenhouse gases would be lessened. Secondly, moving people outside reduces their dependence on a controlled, air-conditioned environment and we would undoubtedly see behavioural change within our buildings as an outcome. And finally, that there would be less need for roads and thus smaller surface area of a particularly high-heat emitting surface.