A group of industry experts have concluded that green roofs are best able to cope with the expected impacts of climate change - higher wind speeds, heavier rainfall in winter and longer, hotter summers.

But the design of green roofs should be looked at carefully, says the say the Building Research Establishment Ltd (BRE), who have produced a design digest, Reducing the effects of climate change by roof design.

Green roofs are vegetated roof covers, with growing media and plants taking the place of bare membrane, gravel ballast, shingles or tiles. The number and placement of layers vary, but all generally include a waterproofing layer, drainage, growing media and plants, covering the entire roof deck surface.

A key features of green roofs is the cover given to the waterproofing membrane, which prevents exposure to UV light and extremes of weather. Green roofs cope well with windy conditions, and release rainwater slowly so reducing the risks of flooding.

However, Gerry Saunders of BRE warns, “High quality materials and methods of installation are needed to ensure that the green roof stays watertight for the lifetime of the building.”

The green roof can have other benefits when significant numbers are built in urban areas, such as improved air quality and the filtering of acid from rainwater. But as the initial construction costs are higher than other design options, some form of government incentive scheme may be needed to kick-start the use of green roofs in UK urban areas.

More information is available in a new BRE Digest, produced as a part of a DTI / Industry funded project. Digest 486 Reducing the effects of climate change by roof design is available from BRE Bookshop www.brebookshop.com, tel 020 7505 6622.