SA Roofing September 2017 // Issue: 93 - Page 21

FEATURES A green roof overlooking Pretoria CBD. planned during the integrated design phase. Factors to consider include the sun, wind loading, dead loading and shear forces, waterproofing, drainage, fire, irrigation, safety and access,” says Ferreira. A reinforced concrete roof structure must be waterproofed before a garden can be created on top of it, according to waterproofing experts Penetron. Other considerations include accessibility, structural considerations, roof type and slope, safety and accessibility, types of green roof systems as well as diverse types of drainage materials and technologies. A thorough process of installation is required to ensure the garden has longevity and benefits both the building and its occupants. Benefits of a roof garden Clive Greenstone from Green Roof Designs says that urban greening in the form of green roofs and rooftop gardens offers multiple benefits for the human and environmental components of urban systems. “It includes urban agriculture (food sovereignty), herbal medicinal plant cultivation, aesthetic bio-diverse landscapes and psychological values. From an environmental approach, urban greening offers improvements such as reducing the urban heat island effect (which is a result of replacing the natural landscape with hard, non-porous surfaces found in most cities), storm water attenuation and run off reduction as well as increased spaces for bio-diverse landscapes and habitats,” he says. Ferreira states that a roof garden can be an environmental management tool. “Green roofs contribute to both the building’s environmental welfare as well as the surrounding environments probably more than any other building system or technology available to architects, developers and urban planners wishing to address urban environmental challenges. It can be a sustainable urban drainage system (SUDS),” he says. He also mentions that it has been used by cities across the globe as a valuable tool to counter these challenges. The benefits of roof gardens work towards mitigating the effects of climate change on cities. But the benefits of a roof garden aren’t just environmental. “Green roofs attenuate and filter rainwater therefore ensuring that storm water is released into the system gradually, this protects the building and municipal storm water infrastructure,” he says. Green roofs increase the area’s biodiversity and introduce new species, which supports bird and insects. In addition, green roof surfaces stay cool during hot summer days and keep the ambient temperature cooler than the surrounding area and traditional roof types. “The cumulative effect of this combats the urban heat island effect where dark impervious surfaces heat up and retain heat. Essentially green roofs replace the ecological footprint that was lost due to urbanisation and development,” he says. Green roofs also offer numerous benefits for buildings such as increased amenity space, protection of the waterproofing membrane and insulating the building in summer and winter. “Recent surveys have shown that buildings that incorporate green roofs and living walls may increase the value of the property by as much as 25%. Green roofs also offer the opportunity to practice rooftop farming and so contribute to food security and potential job creation,” Ferreira says. Installing a roof garden The kind of vegetation that is placed on a roof depends on what your requirements are. The plant types that are specified for green roofs can be motivated by RESIDENTIAL // COMMERCIAL // INDUSTRIAL SEPTEMBER 2017 19