We live in a country where nature is unfortunately quite scarce, and where land is a very expensive commodity. The urban sprawl is replacing the natural environment with paved and concrete structures at an alarming rate, leading to a loss of the drainage layer found in nature, and contributing to more frequent and intense flooding events. Furthermore, traditional roofing materials absorb the sun’s radiation, raising the temperature of the roof surface faster than the surrounding air temperature, making the overall ambient temperature soar and leading to the heat island effect.

One way of reversing the negative effects of these two phenomena is by reducing the amount of hard surfaces on our buildings and replacing them with landscaping and roof gardens, which our flat and accessible roofs are ideal for. Green roofs can help with controlling storm water runoff which is the main cause of flooding, reduce storm water runoff and enable the rainwater management system to be reduced in capacity, resulting in a reduction of construction costs.

Other benefits of green roofs include:

Water retention

The drainage layers in a green roof system consist of water retaining troughs which collect and store water that is available for the plants to grow. Drainage elements can store up to 27 litres of water or more, depending on the type.

Improvement of microclimate

As rainwater evaporates, it humidifies the air above it, cooling the air. Ambient air temperature is reduced, improving the microclimate and significantly reducing the heat island effect, and making life more comfortable for residents.

Reduction in energy costs

A green roof buffers temperature extremes and improves the building’s energy performance. As the rooftops become cooler, the building’s AC units become more efficient, and electrical demand is reduced.

Dust and toxic particles binder

Green roof vegetation helps purify air by filtering out 10-20 per cent of dust and smog particles from the air. Additionally, nitrates and other harmful materials found in rainwater are absorbed by the plants or bound in the substrate, improving the quality of the storm water.

Protection from noise pollution

Planted areas are natural sound insulators, absorbing more sound than hard surfaces. Green roofs have the capability to reduce the reflective sound and improve sound insulation. This is very effective for buildings near airports, nightclubs, factories or busy roads.

Reduced renovation costs

A green roof protects the waterproofing from climate extremes, UV exposure and mechanical damage, greatly increasing the life expectancy of the waterproofing and resulting in reduced maintenance and replacement costs.

Recyclable materials

Recycled and recyclable products such as rubber, polyethylene, expanded polystyrene rigid foam, and more recently, biomass materials such as sugar cane are used in the production of drainage elements.

Provide natural biodiverse habitats

Landscaped roofs compensate for the green spaces lost to building development acting as breathing spaces for the urban areas. Green roofs also provide natural habitats for wildlife and help bring nature back into the cities and to our lives.

As society strides relentlessly towards larger urban centres with taller bigger and more complex buildings, green roofs represent one of our best hopes of an environmentally friendly and sustainable architecture.

Frank Muscat is RIBA chartered architect – International Green Roof Association Member.

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