The ancient phenomenon of green or ‘sod’ roofs go back as far as the 6th century BC. and has become a well entrenched practice in Scandinavian and European countries over the past 30 years. Some of the oldest examples of green or ‘sod’ roofs can be seen in Iceland, with many remaining functional and open to public viewing. A functioning old parish church located in Vidimyri that was built in 1834, is one of Iceland’s six ‘sod’ churches still standing, and has been declared a national monument.
Although Vernacular architecture of the 60’s illustrates this contemporary form of design most prolifically, one of the earliest masterpieces was designed by LeCorbusier, a pioneer of modern architecture. In 1929 this French architect designed the famous house Villa Savoye near Paris, that incorporated a multitude of forward thinking elements including a rooftop garden, featuring both plantings and sculptural shapes.
Green Roofs Australia president, Sidonie Carpenter said at the recent Green Building Council SA convention in Cape Town that converting existing roofs into green roofs, and incorporating green roofs into newly designed structures, is a developing trend globally. Carpenter said that sustainable rooftop gardens are gaining popularity in North America and Europe, where as much as 10 to 15 percent of roofs in Germany are green. She said that modular ready planted green roofs are fitted onto new buildings, and cost effective drainage cells can be incorporated from the outset. Many pleasant green roof surprises include that of Swedish dog owners who plant greenery on the roofs of dog kennels for insulation against freezing temperatures, and perhaps the most unusual being the sight of a green taxi roof in Shanghai.
But, said Carpenter the benefits of green roofs extend only as far as the human interaction required for sustainability, and that greenery often dies or roof leak due to a lack of sufficient human care. When properly maintained, the rewards reaped from green roofs include storm water drainage management, rainwater catchment, insulation, the lowering of urban temperatures, visual aesthetics, design opportunities, and the produce from planting such as herbs, vegetables and fruit.
The nature of green or living roofs are different, with some methods of construction differing between pitched green roofs and flat green roofs, whereas existing roof structures or brown roofs can allow for relatively shallow planting in approximately 300mm, while heavier weight bearing structures require greater maintenance.
Discussing urban roof top gardening at the convention was Cape Town horticulturist Zayaan Khan who showed aerial visuals of the city illustrating the near non-existence of green roofs in urban spaces. Khan said the Ethekwini Municipality green roof pilot project launched by the Kwa Zulu Natal Department of Environment Affairs in 2009 has contributed enormously to increased awareness, education and future benefits of rooftop urban agriculture. She said that through the utilization of unused spaces on top of houses, apartment buildings, industrial parks, hospitals, schools and restaurants, green spaces can be created to produce a number of benefits, including food production, insulation during winter and cooling during summer. Rainwater catchment systems can provide water for irrigation especially on domestic green roofs, while waste water from air conditioning systems can be re-directed to irrigate roofs.
Going beyond the reduced food miles that lowers the carbon footprint of under utilized spaces, Khan said benefits of green roofs that convert space into urban food producing farms, also result in social, economic and health benefits to communities.