By Curt Brown
Air Quality Leader, Sustainable Merton
Why Living Roofs?
I remember completing my first living roof several years ago. I had connected a water butt to the down pipe in anticipation of the usual high volume of rain water after a typical Spring downpour. Several downpours had occurred, so, with my watering can in hand, I meandered down the garden path to the water butt and turned the tap. Half way through the second fill the water slowed to a trickle. Suspecting a blockage, I removed the lid to find the container almost completely empty.
The previous winter had been the first time since moving in, over a decade ago, that I had seen the storm water levels on my street rise to cover the pavement and lap against the step up to my front garden. Staring into the empty water butt I began to realise the important role that green infrastructure, and living roofs in particular, had to play in the urban environment.
I had just completed a degree in architecture. It had been enjoyable, but through the inevitable difficult periods, the garden environment had often been just as important to me as my time in the campus classroom and workshop.
I have no doubt about the ability of nature to nurture our wellbeing, and have come to realise that good architecture and urban design can, to an extent, do the same. However, such success depends on the way architecture relates and facilitates our access to the natural environment. The two are not mutually exclusive.
Living roofs are just one form of combating the climatic challenges we face in urban environments. With so many flat roofs that increase volumes of storm water run-off and intensify the heat island effect, the benefits of employing living roofs far outweigh any perceived disadvantages.
Living roofs can:
- Reduce and slow rain water run-off, reducing localised flooding and the strain on storm water systems.
- Reduce the heat island effect, reducing urban temperatures in hot weather, and in turn reducing the need for environmentally unfriendly forms of air conditioning.
- Aid improvement of air quality. In reducing the heat island effect, green roofs help tackle a source of exacerbation of ground level pollution. They can also help to filter airborne particles and heavy metals from the atmosphere and surface water run-off.
- Be designed as habitats that cater for local wildlife, often displaced by urban developments.
- Prolong the life of the supporting roof structure by protecting the waterproof layer from the damaging effects of the elements.
- Help reduce noise pollution.
- Be more aesthetically pleasing and interesting, directly affecting the wellbeing of the observer.
Potential disadvantages include:
- Increased initial capital cost of roof (both supporting structure and actual living roof).
- Increased maintenance (though this depends on the type and design of the living roof).
Living roofs have increased in popularity in the UK over the last decade. Sedums are at the forefront of plants used for living roof installations due to their ability to withstand harsh environments. However, situations often permit designs which accommodate a more diverse palette of planting that can be of more interest and benefit to both us, and the local biodiversity.