Eco Green Roofs were asked by Westfield, Stratford to help rectify some of their failing green roofs. Originally installed just before the Olympics, several roofs on the shopping centre and on the Holiday Inn hotel had failed to vegetate and in many cases were left looking bare. The original design had used a growing media of demolition rubble and had not been considered appropriately from a biodiversity perspective.
Eco Green roofs therefore put forward several options to improve the roofs – although we were unable to remove any of the original green roof elements. Westfield decided to take out our Gold Package, whereby we fitted the roofs with separation and drainage layers, added 5 different substrates to provide a mosaic of habitat areas and plug-planted/seeded the roofs to provide good vegetation growth.
We used our own extensive and biodiversity substrate blends plus 3 other bespoke mixes designed by our in-house green roof ecologist Dr. Chloe Molineux. In areas that we worked on we created undulations in the growing media to provide the roof with more interesting topography; as well as adding sand piles, log piles, cobbled areas and bird/bat boxes – all to maximise the potential biodiversity of the roofs and encourage many invertebrate, bird and other species to utilise the roof space.
We completed the roofs by adding two types of planting; wildflower plug-plants and seeds which were carefully selected to provide a diversity of local flora that should be a good nectar source for invertebrates over an extended period, and wildflower mats to the hotel’s roofs in order to provide more instant aesthetic value.
The Westfield project was a prestigious re-fit of bio-diverse roofs where substrate originally used had been inappropriate and had failed to yield the requirements originally specified
Bio diverse systems often fail to vegetate because the materials used to form the substrate beds lack any significant water holding capacity to encourage immature plant and seed establishment. This leads to invasive weed development and poor species diversity. Whilst this is deemed acceptable within bio diverse standards, some urban developments require a greater control of species diversity to ensure the roof system does not become a weed bank for the surrounding environment that encourages the wrong species to thrive.
The project brief was to blend and improve the existing roof materials without removal, improve drainage and water retention qualities of the substrate and provide a thriving eco system of surface materials, habitats and bio diverse structure to maximise the establishment of multiple plant, insect, bird and bat species.
Bio-diverse roofing often requirers a functional result but the Westfield project required an immature system to be aesthetically pleasing as well as functional and to establish with minimal intervention. This led to a careful design process of roof contour, component usage and habitat provision to ensure species sustainability was ensured.
The roof situation prevented material removal so Eco Green Roofs blended the existing material with multiple substrates to provide a complex set of bio-diverse eco systems that offered a range of environments for invertebrates, insects and over 30 plant species identified as important to the project directive.
Over 1500sqm of failing roof system was re worked to achieve a highly functional bio-diverse platform for the sustainable development of plant, bird, bat and invertebrate species.
Plug plants and seed were carefully selected and the the roof was contoured with waves of differing substrate that offered and encouraged species development. The roof was extensively designed to provide a range of habitat zones to meet the demands of multiple species of insect, bee and bat species identified in local and site bio-diversity assessments. Complex wildflower systems were used where instant impact was required and the species used were blended with the more diverse roof areas.
All of the green roof substrate blends were scientifically designed to be compatible and improve the existing roof materials. Eco Green Roofs managed and designed all substrate mixes to ensure the roofs provided the most sustainable and ecologically diverse environment possible based on the project product restraints.
Conventional bio diversity and sustainable system construction increasingly conflict and Eco Green Roofs supports the blending of the original bio diverse concepts pioneered by Living Roofs.org and Dusty Gedge with the developing multiple diversity and sustainability requirements of an urban green roof. Roofs must now consider and allow for water management, storage, substrate performance, system, function and aesthetics to meet the demands of the emerging market.
A green roof must be much more than simply a place for reused and recycled materials to be placed. It has a core function in the development of the urban landscape and every system requirers careful blending to ensure its environmental capacity is suited to its location and the demands that may be laid upon it. Eco Green Roofs are passionate about the sustainability of every roof they install and insist on a complex design process that ensures a high quality result every time.