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Understanding living walls


Dr Hasim Altan.

Research at Sheffield University aims to produce hard facts about the best ways to design living walls, and to assess what benefits they can offer.

Seen by many as embodying the on trend concept of ‘urban ruralism’, living walls loom large in the imagination of developers and designers, and many of the environmentally aware general public, as a perfect way of literally ‘greening’ the built environment, by increasing biodiversity, improving air quality and mitigating traffic pollution.

More cynically, many architects and would-be developers see green walls as a means of boosting a project’s BREEAM credentials in the quest for planning permission.

But just how sustainable vegetated walls and screens really are is a subject for heated debate, particularly given the failures of a number of high-profile examples. Most infamous has to be the 2009 death of the hundreds of plants comprising London’s first living wall, at the publicly funded Paradise Park Children’s Centre in Islington. This welldocumented disaster was attributed to a broken watering system.

While still a relatively new phenomenon in the UK (certainly when compared with living roofs) the seemingly wide variety of living wall systems on the market is bewildering for specifiers, a situation exacerbated by manufacturers’ and contractors’ extravagant claims regarding the environmental benefits their systems can deliver. They are also perceived by many as expensive and difficult to maintain. A research programme now under way at the University of Sheffield will, for the first time, provide much-needed technical data on the performance of vegetated/living/ green walls.

‘Studies have shown that covering the surfaces of buildings in urban environments with green plants results in an improvement in air quality, aesthetics and wellbeing,’ says principal investigator Dr Hasim Altan from the university’s school of architecture. ‘However, most of these studies took place in climates significantly warmer than the UK. Our study will find out how living walls fare in the UK’s weather and how they can be of most benefit in this country.’

It is important to investigate factors that could affect the success and the environmental performance of living wall systems, Altan says, in order to establish practice guidelines. ‘It will encourage people to choose effective ways of incorporating this new concept into practical building design and optimise the benefits.’

The study is being carried out in collaboration with a living roof and wall contractor Scotscape and is funded by the UK Engineering and Physical Sciences Research Council (EPSRC). Altan describes it as ‘the first bridge between the rapidly growing “green wall” industry and academic knowledge’.

It will quantify the long-term effects of living wall systems in the UK climate over all four seasons, says Altan, who as well as lecturing in sustainable environmental design is director of the BEAU (Buildings Environments Analysis Unit) Research Centre and SaBRE, a joint venture between the university and the Building Research Establishment.

He and his team have installed test beds of three different types of living wall systems (container-based, compostbased and hydroponic) and two types of climber-covered screens on the southwest wall of the George Porter Building at the university’s North Campus. One soil module contains the ivy Hedera Helix Green Wonder, while the other has been planted with the black grass Ophiopogon.

The thermal data within each system, wall surface temperatures behind them and the internal and external air temperatures are being recorded for a year, until autumn 2013. The first six month’s data will be processed and published this summer. Detailed analysis will then be carried out to look at how the systems have functioned differently ‘in relation to variation and climatic conditions’. The observational data will also help to validate computer simulation results, enabling the researchers to clarify the benefits of vegetated walls in improving a building’s energy performance and the indoor thermal comfort of its occupants.

As the initially high installation cost of living walls is ‘the major disadvantage of promoting the practice’, Altan explains, ‘it is vital to clarify the benefits for investments’. The Sheffield study will, he says, ‘provide the knowledge of quantifiable data that will help businesses and individuals make informed decisions and choices when they consider building specifications’.

The study is also looking at the consumption of irrigation water required for each system. ‘There have been concerns regarding the maintenance and environmental costs of keeping living walls thriving, especially the requirements for mains water,’ Altan says. ‘The monitoring will provide a good indication as to which system is most efficient and possible ideas for future improvements.’

This is not the only research that is taking place. The charity Buglife is assessing the benefits of living walls in terms of providing habitats for essential invertebrate life, birds and bees, and is undertaking quarterly analytical assessments to monitor the rich variety of ‘birds, bugs and bees’ which gravitate to areas of biodiversity in urban areas. And Juri Yoshimi, a PhD student and Altan’s research assistant, is undertaking research in parallel to the living walls project, exploring green walls and their thermal effects, using a long-term monitoring and simulation study.

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