How Green Roofs can Improve our Cities

The smartest designs are an active part of local ecosystems: they harness heat from the sun, facilitate the flow of fresh air, or take advantage of trees and hillsides for shelter. And they give back, too: habitats for wildlife, drainage for stormwater, greenery to keep a dense city block cool.

The value that local ecosystems offer urban areas is just beginning to be recognised. A recent study in New York City found its trees to be worth $122 million thanks to their part in reducing pollution, improving aesthetics, and keeping inner city temperatures comfortable [see 'What's a tree really worth?']. But these ‘services’ are rarely factored in when planning teams get to grips with a retrofit project. Their rigorous assessments may cover a whole range of technologies, assessing their potential energy savings, costs and returns, but they may not take into account the benefits a green roof could offer. They try to minimise the cost to the planet through carbon emissions, but may not account for the cost of a newly sealed loft to any bats hanging out in the ’hood.