Urban Air Quality, Green Building Envelope

A report from global firm Arup examines impacts of vegetation on the building envelope in cities. Is it more than "architectural window dressing?"

A new report from Arup, a global firm of firm of designers, planners, engineers, consultants, and technical specialists, examines the contribution of “green building envelopes,” such as moss and vegetated walls, vertical farming, and roof gardens, to improved air quality has been underestimated. The report, “Cities Alive: Green Building Envelope,” reviews green infrastructure schemes across five 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.

building envelopeAccording to Arup, green envelopes, often dismissed as “architectural window dressing,” can reduce localized air pollution by up to 20% in some locations, rapidly reducing toxic air at street level.

For the report, 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 U.S. study, urban areas with a population exceeding one million can be up to 12°C warmer in the evening than surrounding areas, and in particularly dense centers, 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.

“Tackling rising air pollution is a priority to help improve people’s health,” said Tom Armour, global landscape architecture leader with Arup. “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.”