Green roofs reduce energy output, create habitat and protect building materials.
Benefits of living rooftops
By the time I reached the observation deck on the 124th floor of Burj Khalifa my mind was buzzing with superlatives. Like Charlie in the great glass elevator, I had just travelled at a speed faster than free-fall to a 360-degree viewing platform almost 650 metres above Dubai. There, I had entered a world that belonged more to the grandiose plans of property developers than the reality I had left a minute earlier.
Buildings that I knew to be real looked like the architectural models I was used to seeing at Cityscape, while the usual traffic free-for-all on Sheikh Zayed Road had assumed the character of a calm processional. From such an elevated perspective, everything seemed possible and I found myself daydreaming about how the view might look if one of Dubai Municipality's more adventurous and contentious schemes became a reality and every roof in the city was turned into a vegetated oasis.
A city full of living roofs may sound like the stuff of eco-fantasy but in many cities around the world it is slowly becoming a reality. Green roofs have recently been installed on high-profile buildings such as the Museum of Modern Art in New York, the California Academy of Sciences in San Francisco and Al Shaqab Equestrian Centre in Qatar. Dubai Municipality launched its Green Roofs initiative in 2008 and, since then, has been conducting a public awareness campaign about the benefits associated with them. These range from helping to reduce the money and energy spent on air conditioning, to air purification, heat and sound insulation, and the creation of valuable habitat for birds and other animal species. A living roof will also act as a protective layer for the constructed roof below - a serious issue in the UAE, where extreme heat and solar radiation cause roofing materials to deteriorate far faster than they do elsewhere. The widespread installation of living roofs would also help to combat overheating in urban and suburban areas and this is one of the main reasons why governments, designers and environmentalists are so keen on them.
Dubai Municipality kick-started its campaign by testing different systems on the roofs of its own offices, and vegetated roofs are now also starting to make an appearance in new developments such as Wafi City Mall and Mirdif City Centre in Dubai and the Central Market development in Abu Dhabi. For the programme to be a real success it will have to tackle the issue of how living roofs can be retro-fitted onto older buildings and how this can be implemented when most properties are rented.
Given that many more of us have access to our rooftops than to open space at ground level, it's not surprising that I'm often asked for advice about rooftop gardening.
Weight, access, water and shade are the key criteria and you should ask yourself some very basic questions about each before deciding to create your own Hanging Gardens of Babylon.
Most roofs will be strong enough to support a modest collection of plants in carefully selected containers; however, if your ambitions extend beyond this it is very important to consider the strength of your roof. If in any doubt, seek expert advice from a landscape designer, architect or structural engineer. Access is also key, as it will determine your ability to build, maintain and ultimately enjoy your roof garden. Just how easy will it be to get your pots, plants and soil onto the roof and how easy will it be for you to reach them on a daily basis? (This is essential in summer when your plants require frequent check-ups and TLC.)
The issue of irrigation is inextricably linked with your roof's orientation and the availability of shade. Without an external water supply, an automatic irrigation system and a means of providing shade for your plants you will struggle to maintain a roof garden because the extremes of heat and wind up there are even more severe than at ground level.
Even with regular irrigation and shade, you will need plants that are extremely heat-, drought- and wind-tolerant for them to thrive on a south- or west-facing roof. Most tropical plants will struggle and never establish themselves sufficiently to really flourish.
In the next column I will look at how best to reduce weight, provide shade and select the right plants and outdoor furniture for your roof garden.
* Nick Leech
Useful resources and links: Dubai Municipality Green Roof Manual, www.dubaibuildings.dm.ae; Al Yousuf Agriculture and Landscapes, www.alyousuf.com; a DIY guide to creating your own living roof: http://livingroofs.org