‘Living walls’ can play a significant role in tackling toxic air hot spots in cities, says the report. It highlights the contribution of ‘green building envelopes’, such as moss and vegetated walls, vertical farming and roof gardens.
Worldwide, 3.7 million premature deaths in 2012 were attributed to exposure to poor air quality. Approximately 200,000 of these were in Europe and 900,000 in south-east Asia.
Green envelopes, often dismissed as “architectural window dressing”, can reduce localised air pollution by up to 20% in some locations, rapidly reducing toxic air at street level, says Arup.
“Tackling rising air pollution is a priority to help improve people’s health,” said Arup global landscape architecture leader Tom Armour. “As our cities continue to become built up, ‘grey’ structures, such as walls and roofs, are a source of untapped potential for adapting into green spaces. When well-designed, green envelopes can have a positive impact on tackling air pollution, but can also deliver a wide range of social, economic and environmental benefits to make cities more attractive and healthier places to be.”
The report called Cities Alive: Green Building Envelope reviews green infrastructure schemes across five global cities; London, Los Angeles, Berlin, Melbourne and Hong Kong to quantify the benefits of ‘green building envelopes’. It is the fourth report in the ‘Cities Alive’ series which looks at ways to help shape a better world.
Advanced computer software was used to provide a visual representation of the flow of gasses, and help determine the effectiveness of green building envelopes to reduce pollutant concentrations. The report highlights plant species, such as pine and birch, that are particularly effective because of their ability to capture large quantities of particulate matter, including during winter when pollution concentrations are highest.
The study also highlights that green envelopes can reduce sound levels from emergent and traffic noise sources by up to 10 decibels in certain situations. To the human ear, this could make traffic sound half as loud. Increasing the quantity of vegetation in a city can also reduce temperatures. According to a US study, urban areas with a population exceeding 1 million can be up to 12°C warmer in the evening than surrounding areas, and in particularly dense centres, green infrastructure could reduce air temperature by up to 10°C. Green envelopes can also reduce peak energy consumption in traditional buildings by up to 8%.
As cities become more densely populated and increasing pressure is put on existing parks and open spaces to make way for further development. The report shows how green buildings can play a significant part in reducing urban stress and keeping people connected with nature. Vertical and urban farming are also highlighted as great ways of being able to create community spaces.