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Natural approach to preventing building overheating

Indian bean tree (Capalpa bignonioides) Borrelli Yard (copyright Peter Bridgeman)

A natural approach to preventing building overheating

New requirements to limit overheating in new buildings were introduced at the end of last year to tackle a predicted rise in heat-related deaths due to climate change. There are currently 2000 deaths a year in England and Wales, with numbers expected to rise to 6,000 a year by 2050.

The regulations look at factors such as building materials, window sizes and openable windows for passive heat reduction. There are concerns that if houses are too hot to live in they will end up being retrofitted with air conditioning.

External factors such as the cooling impact of trees, plants, grass and water do not form part of the calculations, but are proven to have a beneficial effect on external temperatures and human comfort. Therefore setting aside space for well-placed trees, ponds, and planting when designing new homes would make an additional contribution to cooling.   

Trees prevent buildings warming as they physically block short wave radiation from the sun touching walls, windows and roofs. They also release moisture through their leaves which reduces leaf temperature cooling the surrounding air. Those combined effects have a significant effect in urban areas where heat is stored in hard surfaces and released at night, preventing surrounding homes from cooling down.

Further research has shown that the cooling and shading effects are more pronounced in healthy and fast-growing trees, with a direct link being made to the planting conditions of the trees (Rahman et al, 2011). For example, trees grown in less compacted structural soils grow more quickly, have a better physiological performance and provide five times greater cooling than the same tree planted in a highly compacted soil.

So a properly planted deciduous tree to the south or west of a building would cost a fraction of sun louvres and probably outlast the building.


Part O, 2021 ed.

Tree pit design

Georgina Harvey

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Georgina Harvey

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