The Welsh School of Architecture at Cardiff University found that leafy walls and roofs could help people turn down the air conditioning on hot days, thus saving energy.

Professor Phil Jones and PhD student Eleftheria Alexandri used computer models to compare the impact of “greening” buildings in nine cities, including London, Mumbai, and Brasília.

Professor Jones said using temperature data from each city’s warmest month, the research found that the air around every building would be cooler by up to 11C with green walls and roofs.

He said, “The hotter the climate, the greater the cooling effect.

“Greening buildings will not only make cities more comfortable to live in, but could also save energy by significantly reducing the demand for air-conditioning on hot days.”