When British Land first started creating green roofs on various London office buildings in 2004, it was challenging to take the idea from an ecologist’s vision to the reality of a planted, healthy landscape. As a client, we were testing a new idea. We often needed to introduce our architects, structural engineers, contractors and property management partners to the concept – and then develop and test strategies together to deliver quality natural habitats on commercial buildings. Over the years, as we have installed different green roof styles and commissioned studies, we have learned and shared many lessons.
Today, we know more, for instance, about drainage and the potential for (or, more often, lack of) water retention. We understand the need for roof and terrace access to align with internal floor levels. We know which substrates last through British winters and how to plan for rooftop winds. We recognise issues and opportunities relating to visibility from surrounding buildings, and more. Happily, we have not been the only ones to recognise the benefits of green roofs and to learn these lessons.
Green roofs have gone mainstream around the world over the past 10 years. From London to Sydney, Hamburg to Istanbul, Singapore to Rio de Janeiro, they are a recognised strategy for urban green infrastructure. In London, there are now about 700 green roofs, covering 175,000 m2 . I am pleased that British Land has played a small but important part in this success story – creating green roofs on 12 new buildings and retrofitting three on existing buildings, with more on the way.
Green roofs are no longer an unusual concept, and there are standard design formats and green roof types that architects and others understand and can design or install. However, many of the technical benefits of green roofs remain to be analysed and understood. And so this book and the research it describes are much needed, particularly at a time when strengthening urban resilience is a critical policy issue. Of particular relevance to cities and property owners are the prospects for retrofitting green roofs and the infrastructure benefits that all green roofs provide. Given the acres of existing roof space in cities around the world, what kind of buildings are particularly suitable for the additional structural load of retrofitting green roofs?
With increasing incidence of flooding in many areas, how much rainwater can a 50 cm soil substrate attenuate, and can we make basement flood attenuation tanks correspondingly smaller? Also, how can we deliver green roofs that fulfil multiple functions, such as biodiversity, human enjoyment, aesthetics and food production? Approaches to modelling urban heat island impacts are particularly useful for policy‐makers. As climate change increasingly affects city temperatures, with knock‐on effects on people’s health and energy consumption, it is important to be able to calculate the benefit of green roofs for temperature management.
Likewise, the proposed methodology for calculating the attenuation potential of green roofs should be of immediate assistance in factoring green roofs into strategies for our changing weather futures. In addition, this book helpfully advances research on the social and biodiversity functions of green roofs for organisations interested in strategies to support human health, ecology and food production in urban areas. An in‐depth analysis of a range of case studies explores how green roofs fulfil a range of functions – adding visual interest, creating garden spaces, growing food, introducing habitats for animal biodiversity and contributing to healthy environments through air‐quality filtration, water management and temperature control.
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