T he air above our cities is hotter than the air above surrounding rural areas. This phenomenon is called the ‘urban heat island’ effect. The primary reasons for this are densely constructed structures, supporting infrastructure and extensive traffic within our crowded cities. In Chennai, for instance, the increase in temperature is as high as 5 degrees Celsius when compared to its outskirts.
The population of urban India is estimated to reach 600 million by the year 2030. Current statistics stand at 450 million. This alarming estimated rate of migration of almost 25 people per minute into our cities means the need for more construction, more traffic and subsequently, more paved areas and less tree cover. This uncontrolled expansion will only lead to further overheating, leading to extremely unhealthy living conditions for city dwellers.
Considering these consequences, it is imperative that we focus on urban development that is smart, eco-friendly and sustainable to mitigate heat and to stay healthy within our cities. So, what can we do to help?
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Plant more
It goes without saying that trees and plants not only provide us shade, oxygen and biodiversity, but also help our cities stay cool. It is unfortunate that one of the first steps taken in any development is to cut existing trees and clear vegetation to make way for our buildings.
We need to be conscious of not cutting down trees mindlessly and instead, plan our construction around them. Roof gardens are an excellent way to add that touch of green as well cool our concrete rooftops, thus reducing radiation from concrete. Vertical gardens are an option for our vertically oriented high-density city construction.
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Minimise paved areas
A major contributor to the urban heat island effect is the extent of impermeable paving in our cities including roads, side walks and other paved areas which absorb and radiate midday heat into the atmosphere during cooler evenings. If this paving was replaced by soil or grass the radiation will be much less. As an added benefit, rain water percolation into the ground would also increase.
Considering that we cannot eliminate paving completely, we could at least minimise the same. We should judiciously plan such surfaces only where we need them and leave the rest of the ground permeable to allow for both, water percolation and reduced temperatures. For example, driveways and walkways should be planned just for the minimum width and length required, and not construct them excessively wide or long. Grass pavers which have a minimum of 30% of openings are also an option for driveways and parking lots. Lighter coloured pavers reflect more and absorb less heat, thus serving as better paving option.
These measures, along with the sensible selection of materials and minimal use of automobiles, will go a long way in reducing urban heat islands within our cities and mitigate global warming.
The author is the founder of Green Evolution, a sustainable architecture firm