The green green grass of… roofs!

The demand for green roofs is growing.

In recent years, green roofing has blossomed into a mainstream flat roofing system. Everyone from architects and contractors, to home owners and especially local planning authorities have recognised its benefits. As a result, green roofs are sprouting up just about anywhere. If you’re keen to know more about Green Roofs read on…


It is now widely recognised that extensive planting within urban areas is a great means of improving air quality. Naturally, that means green roofs can contribute to the reduction of a number of polluting air particles – with plants reducing carbon dioxide in the atmosphere and producing oxygen. They also improve water quality by helping to prevent polluting particles entering the water system through surface run off from the roof.


Green roofs are intrinsically of greater benefit to biodiversity than more traditional roofing methods, and they provide many benefits for wildlife compared to non-green roofs. The biodiversity of green roofs can be enhanced even further by the placing of objects such as dead wood and old branches, and being designed to meet specific local biodiversity needs.


The thermal performance and roof insulation for buildings is recognised as a huge benefit of green roof systems. A green roof not only acts as an insulation barrier, the combination of plant and soil processes reduces the amount of solar energy impacting the building. In winter root activity of plants, air layers and the effect of the entire green roof system create heat and thereby provide a natural insulation membrane.


The urban heat island effect is the difference in temperature between urban areas and the surrounding countryside – in part this is due to large areas of hard reflective surfaces and can be as much as a 5oC difference. Green roofs help to absorb heat reducing urban temperatures, and subsequent improvements in air pollution.


Sound waves are absorbed, reflected or deflected by the combination of soil, plants and trapped layers of air within green roof systems – creating a sound insulation barrier and reducing sound compared with a conventional roof system. The growing medium tends to block lower sound frequencies, whilst the plants block higher frequencies. The amount of sound insulation is dependent on the system used and the substrate depth.


Recycled materials are used in the membranes and growing mediums, making green roofs even greener! By using crushed porous brick or on-site aggregate (which is regularly taken from the original site), green roofs decrease the need for waste disposal to landfill and transportation to disposal of waste.


Green roofs are a fantastic store of rainwater with slower evaporation of water into the atmosphere. As much as 70-80% of rainfall is retained in the summer with between 25-40% in winter. Green roofs also reduce and delay run off during times of heavy and prolonged rainfall. Green roofs, therefore, reduce the impact of run off of heavy rainfall reducing the likelihood of local flooding.


The value of green spaces to people living and working in towns and cities has been increasingly recognised in recent years. Green roofs not only help perform an ecological function, visually soften the built-up environment and support biodiversity – they also provide access to birdsong and seasonal colour changes. These are proved to aid people’s mental and physical health, and are attributed to helping to reduce a person’s heart rate and blood-pressure.