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Green roofs and living walls can keep the city cooler, shows new IITB study.

Read time: 2 mins
4 Jun 2018

Researchers from Indian Institute of Technology Bombay, Mumbai are studying the strange phenomenon known as urban heat islands, which leads to a sharp temperature difference between urban and metropolitan areas and the surrounding rural areas, due to human activities. The study also proposes measures to reduce the dire effects of the phenomenon.

Urban Heat Islands (UHI) is a phenomenon where the temperature in urban and metropolitan areas gets significantly higher than the surrounding rural areas. “Heat island forms when the temperature difference between urban area and rural area temperature is significant. The temperature differences are often largest during calm, clear evenings because rural areas cool off faster at night than cities” explain the authors of the study.

Several factors lead to such a disparity in temperatures, like larger stretches of tarred roads absorbing more solar radiation, extensive use of materials like concrete and asphalt, and decrease in amount of vegetation. Adding to these woes is the factor of urbanization, where a population slowly shifts from rural areas to urban areas. Such a mass movement of population has also had an adverse effect on the climatic patterns in our environment.

“It (urbanization) is impacting the temperature profile of the region, the rainfall pattern, the albedo (a measure of the amount of solar radiation reflected), relative humidity, and the radiation pattern” remark the authors of the study.

Changes to the micro –scale environment due to concretization, urban activity and increase in vehicular density are known to cause changes in the macro-scale environment, in urban pockets.

For their study, the researchers studied the outdoor thermal environment at the micro-scale in the metropolitan areas of Mumbai. Using ENVI-met software, the researchers simulated the micro-climate, and explored measures to mitigate the effects of UHI. The study also explores the importance of greening or increasing vegetation cover in mitigating the harmful effects of the temperature disparity.

The study reveals the importance of vegetation in controlling the rising temperature in cities. It recommends the use of vertical walls, also known as living walls or green walls-- which are self sufficient vertical gardens attached to the exterior or interior of buildings. Apart from the green walls, the study also suggests dense vegetation cover and presence of forests in cities to avoid effects of UHI.