WHY WE NEED MORE GREENER ROOFS
Green roofs: they’re more than just ornamental finishes to a building. As we face challenges like warmer cities and decreasing biodiversity, green rooftops are proving to be part of the solution.
In the 1970s Germany showed the world the potential of rooftop gardening. The country was facing severe stormwater problems and adopted green roofs as one part of the answer. Now it is estimated that 15 percent of Germany’s flat roofs are swathed in plants.
More recently, cities like Copenhagen and Toronto have followed suit, with Copenhagen adopting a mandatory green roof policy in 2010 and Toronto now boasting 444 green roofs across the city. Just last year, France also legislated that all new buildings in commercial zones must have plants or solar panels.
Given the Australian climate is so accommodative to green roofs, and so susceptible to severe weather events and higher temperatures from urbanisation, why hasn’t this innovative and increasingly necessary way of gardening taken root here?
The benefits of green roofs
The future of our cities hinges on the commitment to sustainable infrastructure we make today. Not only do rooftop gardens improve biodiversity – an important consideration, particularly for our dwindling bee populations – they also combat other key issues that have arisen from urbanisation.
Around the world, green roofs have proven effective at offsetting the impact of the Urban Heat Island effect and reducing stormwater runoff. In fact, a shallow green roof that’s only 10 cm deep can absorb up to 50 percent of rain that falls on it. The deeper the garden, the more this increases.
Interestingly, New York City is now investing in the creation of more green roofs, in order to mitigate the impact of severe weather in the future. This decision came after Hurricane Sandy caused widespread flooding in 2012.
In terms of sustainable architecture, an irrigated green roof reduces the need for heating and cooling – especially in buildings with poor insulation – which can go a long way to reducing the energy demands of our cities. These types of green roofs also prolong the lifespan of a building, as they provide an extra layer of protection.
Each of these considerations is vitally important, but so are the human benefits of increasing nature in the city. Cleaner air, more spaces for relaxation and beautified cities are all benefits of rooftop gardens that result in an enhanced lifestyle and optimal physical and mental wellbeing.
Case study: M Central, Sydney
M Central in Sydney is one of the most prominent examples of a successful rooftop garden in Australia. Constructed in 2005, it set a new standard for rooftop gardens in Australia. Today, it is still thriving and plays an important role in creating a sense of community amongst the building’s 400+ residents, with many residents admitting the rooftop garden was part of the reason they chose to buy at M Central.
While there are challenges of structural capacity, waterproofing, drainage and plant selection to consider in gardens like this, the environmental and cultural impacts play a significant role in the big picture: creating more liveable cities.
Creating your own rooftop garden
There is a perception that rooftop gardens are expensive to install and maintain. And while that’s true for gardens like M Central, it doesn’t need to be the case. Take the rooftop garden at San Francisco’s The Fairmont Hotel as an example. Installation for a garden like this is relatively simple and extremely cost effective, particularly if you are able to harvest your own produce as the chef does here.
If ornamental gardening is more your style, imagine planter boxes like these teeming with lush grasses, colourful wildflowers or sculptural succulents. For greater vibrancy, consider plants like rhipsalis baccifera (mistletoe cactus), which will flow over the sides of a raised planter.
Generally, the plants that are best suited to rooftop conditions are low maintenance. Grasses, cactus, succulents and natives are all hardy species that will thrive in the exposed conditions.
If every flat roof contained plants, beehives or solar panels, just imagine the impact we could create for generations to come.
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