Green Walls

Walls covered in living vegetation could be coming to a city near you, explains Adolfo Harrison

Our passion for the environment is changing the face of urban design - just look at the explosion in popularity of green roofs in city centres. Instead of dull slate or concrete, architects and designers are increasingly creating roofs covered in living vegetation. Not only do these look incredible, they also boast near impeccable eco-credentials. Little wonder that town planners and mayors are rushing to include them in new developments. But green roofs are often invisible from ground level. And it's the next evolution in sustainable design the lesser known 'green walls' that will leave the most noticeable mark on our cityscapes. In time, it is hoped that these will dramatically improve the health of our cities, indoors and out, from skyscrapers to run-down housing.

Beauty and functionality

It was the sheer beauty of green walls, also referred to as a living wall, which first aroused interest in the 1990s. Today it is their profound sustainable value to buildings and habitats that is exciting designers. The benefits are numerous - green walls cool buildings in summer, retain heat in winter and reduce noise pollution. Green walls can contribute to the 10% of green space city centres need to reduce temperatures by 4 degrees. This is the same amount by which some experts believe temperatures will rise in the next 80 years. Green walls attract wildlife to areas that would otherwise be sterile concrete and glass. They are incredibly efficient at cleaning pollutants outdoors and in. And of course their exuberant displays simply make people happy.

A short history

Green walls started to attract attention in the mid-1990s when Patrick Blanc, an esteemed French botanist, began exhibiting his creations at flower shows. He specialised in plants that grew without soil on the side of rocks and tree trunks, and used this knowledge to conceive the first vertical gardens. Green walls are grown hydroponically- in other words, they don't use soil. The plants are instead grown in pockets of felt or rockwool, and fed by nutrient enriched water. There is a vast plant choice, and this has enabled the subsequent pioneers in France, the UK and Canada to design ever more stunning creations. However, the overall attitude is that beauty is only skin deep, and that the main concern of a green wall should be to deliver environmental and social benefits.

Indoor air pollution

One of the interesting revelations about green wall systems has been the improvement in air quality they can provide. Indoor air pollution is on average 16% worse than outdoors. Green walls have an air conditioning system that draws air through them as part of a biofilter which cleans the polluted air, reducing volatile organic compounds by around 75%. Natural microbes living on and in the plant roots break down the pollution, turning it into food for the plants. This is now being hailed as one of the solutions of Sick Building Syndrome, known to contribute to absenteeism in buildings around the world. Some reports claim that third of absenteeism due to illness stems from poor air quality.

The future

With global energy and food shortages likely to dictate the future of urban life and architecture, buildings that require a lot of energy simply won't be sustainable. With some estimates suggesting that green walls could reduce a building's air conditioning needs by 40%, it's no surprise that town planners are looking to them for solutions. And they are becoming even more efficient. The new green walls being developed today use a quarter less the water than earlier models. This can come from grey water systems, which would also supply the nutrients, and could be combined with rainwater, removing any dependency on mains water. As green walls increase in popularity among architects, the pioneers share the preferred view that the future must involve working with local councils. This way, green walls will reach areas with run-down housing, train stations and even car parks. They also predict that we'll see them used for urban food production too. At present, the high costs of creating green walls make them viable only for commercial buildings. But with demand soaring, it may not be too long before more economical systems are developed for private use. Until then, we can console ourselves with the fact that whenever one is 'planted' in our community we all benefit from it one way or another.