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Grow ivy, cucumber, passionfruit on walls of city buildings: leafy walls and roofs could lower temperatures by up to 11°C, depending on the city

Posted by gmarkets on 10 October, 2007

The greenest cities should be, well, green. Leafy walls and roofs could help people turn down the air conditioning on hot days, saving huge amounts of energy. It could lower temperatures by up to 11°C, depending on the city. Eleftheria Alexandri and Phil Jones at the Welsh School of Architecture at the University of Cardiff, UK, used computer models to compare the impact of “greening” buildings in nine cities, including temperate London in the UK, humid Mumbai in India, and tropical Brasilia in Brazil, reported The Economist, 6/10/2007, p. 6

The hotter the climate the greater the cooling: Using temperature data from each city’s warmest month, they found that the air would be cooler around every building with green walls and roofs. And the hotter the climate, the greater the cooling effect (Building and Environment, DOI: 10.1016/j. buildenv.2006.10.055).

Riyadh, Saudi Arabia: If, for example, a group of buildings in Riyadh, Saudi Arabia, was clad in vegetation, the average temperature in the gap between the buildings would be 9 °C cooler during the day and the top temperature in these spaces would fall by 11 °C.

London and Montreal: In London and Montreal, peak temperatures would drop by 4 °C. Green surfaces lower local temperatures in two ways. Firstly, the green surfaces absorb less heat than typical building coverings, and so radiate less heat back into the immediate vicinity. Secondly, plants cool the air through the evaporation of water as they transpire.

The Economist, 6/10/2007, p. 6

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