A thin, natural fibre mat created in Dubai is encouraging the bloom of rooftop gardens in the city by radically reducing cooling bills due to the double insulation they provide for homes and high-rises.Green roofs are recognised worldwide for helping to reduce urban heat island effect, the term given to the overheating of urban and suburban areas due to increased paved, built-over and hard surface areas.With this in mind Emirati Khalfan Al Rahoomy, chairman of environmental solutions company Landex, spent six years devising Green Mat, made in part with coconut and date palm that traps a lot of water in small amounts of soil.The flat brown mesh could help built-up areas like Dubai which lack natural vegetation grow gardens on rooftops, or any other hard surface in need of greenery, without adding to the country\'s water scarcity.In 2008 Dubai Municipality launched the ‘Green Roofs Initiative\' and announced that at least a third of the surface area of roofs should be green. The new green building code will make it mandatory for all new buildings to have a roof garden. \"Green roofs provide double insulation for the buildings, save on air conditioning, reduce the carbon footprint and can save up to 60 per cent of water compared to a regular garden,\" said Al Rahoomy. \"You can grow grass, organic vegetables on your balcony — you can grow anything on it.\"The lightweight Green Mat looks and feels like a brown, wiry doormat. Shallow five centimetre layers of soil sandwiched between swathes of Green Mat help trap water and keep soil moist, reducing the need to irrigate. It can reduce the weight of a traditional green roof by 500 kilograms, Al Rahoomy said.One square metre of soil, 25cm deep weighs 600kgs. However a Green Mat sandwich of the same size weighs 100kg.In Silicon Oasis, what was once a sandy soil garden in Cedar Villa D1 today is a lush green carpet of grass. The grass sits on a concealed sandwich of Green Mat. Daily drip irrigation for the 100 square metre plot started with nine minutes of watering and dropped to one minute over a year.In 12 months just 4,500 gallons of water was used on the garden compared to 12,000 gallons that would normally be required for a regular plot. \"This is a cost effective ingenious solution,\" said Al Rahoomy. Priced at Dh25 per square metre, return on the investment in terms of water saved is six months, he added. \"We all have to be careful about our water use. Now that UAE nationals are being charged for water, some have done away with gardens and covered them with tiles. Green Mat can replace soil and create a new garden,\" he said.Green roofs protect buildings from extreme solar radiation and help regulate internal building temperature, reducing the need for cooling. Green Mat can be the first step towards installing a green roof. The natural fibres trap water in small soil beds, reducing the need for fertilisers, minimising surface run-off, and reducing water consumption. From / Gulf news