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SWITCH - Green and Brown Roofs

Green and Brown roofs are roofs covered by a growth substrate where plants grow, thus providing some environmental benefits to the urban environment. Brown roofsare a type of extensive green roof trying to mimic brownfields. Green roofs have been shown to be effective for insulating buildings and cooling cities, as well as for increasing roof longevity and improving urban aesthetics.

Among the abundant demonstration activities of the SWITCH project, two brown roof demonstrations were carried out in Birmingham (United Kingdom). The main objective of these projects was to deepen the ability of brown roofs for substituting brownfield habitats, reducing roofs run-off and regulating the thermal energy balance of buildings.

International Convention Centre (ICC): this brown roof had a 300m2 area, and was designed to provide demolition site brownfield type habitat for a rare bird, the black redstart (Phoenicurus ochruros) and other birds, plants and invertebrates. The area was covered by a mix of cobbles, quarried gravel, sand and recycled demolition aggregates. Sand piles were added as a nest site for bees and wasps, and large rocks were used as refuge by invertebrates. Along the roof development, 47 plant species were identified to grow there, among which Viola tricolor (Wild pansy), Viola persica (Common field-speedwell) and Lotus corniculatus (Common bird's-foot-trefoil). Also, 30 beetle and spider species were identified. Only three birds were identified to live on the roof: carrion row, wheatear and pied wagtail.

Birmingham Voluntary Service Council (BVSC): this roof occupied a 100 m2 sub-section of the building. Like the ICC brown roof, it was initially conceived to serve as habitat for the black redstart and a wide range of brownfield associated birds, plants and invertebrates. From bottom to top, this area was composed of the existing mastic asphalt, an anti-root barrier and a mat. This mat was intended for retaining water, but also for protecting the established horizons arrangement from water. A mix of quarried gravel, sand and recycled demolition aggregates was added on the top, and once again log and sand piles were added to shelter invertebrates, insects and birds. Additionally, the roof was seeded with a wildflower mix. To make the evolution of the roof more accessible to people, the BVSC installed a glass paned door to view the roof, and a video camera to display live images in its web. The BVSC brown roof was also filmed for a programme for Teachers TV in 2008. 52 plant and 31 insect species were identified along the roof development. Only three bird species (wood pigeon, carrion crow and starling) were identified to use the brown roof.

Dissemination of information represented a key task for both projects. Thus, diverse activities were organised around these brown roofs: several tours for visiting different Birmingham green/brown roofs, and different presentations and seminars. Additionally, the University of Birmingham brown roof research facility is being used as a teaching resource for the “Landscape and Urban Ecology”, attended by Geography, Environmental Science and Environmental Management students.

 

Source:
SWITCH-Sustainable Water Management in the City of the Future. Deliverable D2.3.1.e: A demonstration facility for the dissemination of green and brown roof techniques and value