A green roof is a lightweight, engineered roofing system that allows for the development of rooftop vegetation while protecting the underlying roof structure. Green roofs can provide some important environmental and human health benefits which include purifying the air, reducing storm-water runoff, lowering energy expenditure as well as a host of other advantages.

In the light of growing concern about climate change, the building industry is working hard towards becoming more environmentally aware and making the most of the ecological solutions on offer. Green roofs have now become one of the key growth areas in this industry’s bid to lower the rising carbon dioxide (CO2) levels in the atmosphere.

One of the main strengths of the vegetation on a green roof is its ability to absorb CO2 as part of the process of photosynthesis. These CO2 emissions will further be cut by the reduced use of air conditioning in the underlying buildings, as green roofs help cool them down naturally.

In the summer months, some cities can be up to seven degrees warmer than surrounding areas, becoming incubators for smog, threatening public health and creating a higher energy demand; this is known as the urban heat island effect. By replacing heat-absorbing tar and other dark roofing materials with plants and grasses, green roofs can lower local temperatures significantly.

At a time when unusually heavy rainfall and flash flooding is becoming increasingly common and damaging, green roofs have also helped reduce their impact on human settlements. This is due to this system’s natural ability to absorb up to 75% of the rainwater falling upon it, helping to prevent localised flooding.

A major source of water pollution is storm water runoff, which carries contaminants, dangerous heavy metals included, from paved surfaces and rooftops to our natural waterways. Another benefit of the absorptive properties of green roofs is that contaminated water is purified as it filters through the layering system and the remaining runoff is therefore pure.

The importance of implementing green roof systems in the urban landscape is finally becoming recognised worldwide as a way of contributing to the economic, environmental and social appeal of a building. Originally inspired by the sod roofs seen in rural Scandinavia over several centuries, green roofs have been adopted by many municipalities as a pragmatic means of ameliorating environmental and living conditions. In Germany, an estimated 10% of buildings now have green roofs. Tokyo implemented the “Tokyo Plan 2000” to ensure useable rooftop space on new buildings larger than 1,000 square meters must be 20% green. Green roofs have also been adopted in the major cities of America and Canada. The UK is now slowly latching on to a concept that is set to become a common sight on the roofs of buildings worldwide.