Want to save the planet? Then grass over your roof

They may look like homes out of Beatrix Potter books, but houses with grass lawns planted on the roof may be the latest weapon in the battle against global warming.

Green roofs, sewn with turf, trees and even herbaceous borders, are to be promoted by ministers who believe they will not only help to absorb CO2 emissions but also improve house insulation and cut heating bills.

Government ministers want a new wave of sustainable buildings, including office blocks, to have living roofs covered with vegetation. The grass roofs will be a valuable garden space for city dwellers and will absorb rain water, filter pollutants out of the air and provide habitats for wildlife.

They have studied evidence that living roofs, first developed in Germany in the 1960s, not only help the environment but also cool down cities. Green roof temperatures have been found to be up to 26C cooler than traditional roofs, reducing urban temperatures by as much as 6C.

The roofs, distinct from roof gardens with potted plants, are planted on a thin layer of soil and can include grass, mosses and flowering plants. Larger office buildings have roof spaces large enough to support small trees, shrubs, flowers and vegetable gardens, which absorb the rain water that usually runs off roofs.

In Germany about 10 per cent of roofs have been adapted to carry vegetation, but Britain has been relatively slow to catch on.

Keen to promote green roofs, the Department of the Environment is working with Yvette Cooper, the housing minister, about including houses with green roofs in their plans for new sustainable housing.

Lord Rooker, the environment minister, said: "A key element of maximising the energy efficiency of buildings is ensuring that they are suitably insulated. Raising building standards will act as a further driver for improving insulation, and green roofs offer one possible solution for delivering better-insulated buildings. Defra, along with other government departments, has been promoting green roofs as part of a wider sustainable construction and will continue their promotion."

In a sign that green roofs are becoming fashionable in Britain, one was featured at this year's Royal Show. The roofs, built on a waterproof membrane, can include root barriers and irrigation systems. They need weeding about once a year.

Chris Huhne, the Liberal Democrat environment spokesman, said: "We have to be innovative, and there will be places where green roofs will fit in magnificently, helping to save water and provide habitats for local species. By absorbing CO2 we can also show that in a small way we are helping to save the planet."

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