SUSTAINABLE BUILDINGS
ANCE TO THE BUILT ENVIRONMENT Tracie Reed, Bauder Ltd
and the reduction in industrial equipment associated with these activities. Further evidence comes from the experiences gained by a building services manager in London, who discovered that the application of a retrofitted green roof on a building which he was responsible for had significantly reduced the need to use the cooling and heating plant on the floor beneath. Since the green roof was installed, the use of both cooling and heating fans had significantly reduced and it is estimated that about 25.9 MW per year is now being saved, which at current electricity rates represents a saving of over £4,300 per year. If the insulating benefits of the green roof to the floor below had been identified and it had been installed as part of the original design for the building, it is estimated that there would have been a capital saving of £10,000, due to reduction in heating and cooling equipment needed for the floor below. For the forward thinking Facilities
Manager, a green roof could well be feasible for the refurbishment of a currently failing roof or indeed for any additional buildings being considered for the expansion of current premises. When considering if a green roof could be successfully included, it is important that a number of preliminary questions are answered: • Is the site suitable for a green roof? – an understanding of the factors affecting a green roof must be understood: climate, building structure, plant requirements.
• What performance is required from the landscape? – is it to mitigate storm water, maximise water retention, offer additional energy savings, provide recreational space, etc
• How is the preferred green roof system to be specified? – is the type of green roof to be extensive for a low maintenance visual effect that will improve the air quality and rain water run off, intensive for recreational use or biodiversity where a particular species of wildlife is to be supported?
• Where do you go to get meaningful advice? – with many people professing to be green roof specialists, who really are the experts with a proven track record and which system will deliver the
technical credentials required?
• How do you obtain meaningful guarantees? – a green roof needs to be able to survive for a long time, and assurances for this are crucial.
SO, HOW IS A GREEN ROOF SUCCESSFULLY INSTALLED? Everyone must be involved and fully support the project! Regardless of the type of roof selected everyone must be involved: client, architect, specifier and the local planning authority. The planner should determine if the chosen roof is feasible at the location and make it clear in the planning constraint the wildlife which is to be targeted for a biodiversity roof. The architect’s main objective is to specify the landscape and its support system, to ensure the structure of the building is not placed at risk. A knowledgeable planning department will pick up any anomalies to the application and insist that all factors be suitably considered. The Local Authority planner will previously have seen numerous applications which simply state that an extensive green roof is required; which can be a problem as there are at least six different variations of this type of green roof. Each variation will need a different balance of growing medium type and depth combined with a range of differing drainage characteristics, to support the proposed vegetation and other elements of the planned micro-ecology. A biodiversity roof needs to specifically state which type of wildlife is to be targeted and which particular plants and habitat items are required, otherwise you cannot be sure what you will end up with.
ESSENTIAL FACTORS TO BE CONSIDERED FOR ALL GREEN ROOFS The first consideration for any green roof installation is the waterproofing system, which should be of high quality and robust; the capping sheet will often be a root barrier to prevent penetration, although this is not always the case, and any alternative root barrier will also need to meet the German FLL standards to ensure its integrity. It is also important to ensure that the roof drainage system is designed to be capable of coping with intense rainfall over short periods, as recommended within the current British
Standards. Safe access for maintenance of the vegetation must also be considered and planned for and the roof should be leak tested before the landscaping is installed.
A VARIABLE FACTOR TO BE CONSIDERED FOR ALL GREEN ROOFS Increasingly, green roof systems are being installed on slopes of in excess of 5°, and these need to be designed and installed in a way to ensure that they cannot slip off the waterproofing. Whilst this is relatively easily achieved on slopes of up to 20°, steeper slopes require more careful consideration and additional restraint of the growing medium. The design of the structure will also be significant in determining if a green roof installation can be achieved.
MAINTAINING A GREEN ROOF Whilst many green roofs are intended to have a “natural” look, it is important to recognise that a certain minimal level of maintenance will be required on every installation, if only to control the build-up of bio-mass and keep the roof outlets free of debris. This should be identified as a key building maintenance requirement from the outset and planned accordingly. Whilst it is not uncommon for the maintenance to be undertaken by the building owner as part of the general management of the structure, it is increasingly common for the work to be undertaken by a local green roof maintenance specialist, trained to work at height and familiar with the requirements for the effective maintenance of green roofs.
There are challenging times ahead for all sectors of the Facilities Management community with many environmental benefits to be gained through the use of green roofs on both new and existing structures. The key to the success of green roofs as part of a sustainable ecological policy will continue to be in depth knowledge and understanding of every stage in their delivery and post installation maintenance. With it, the sky is literally the limit!
Bauder has been delivering green roof systems in the UK for over 30 years with over 450,000 m² of successful green roofs installed to date.
www.bauder.co.uk
SUSTAINABLE FM | JUNE 2010 |55
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