Londons Green Roof Policy

Londons Green Roof Policy

London’s Approach to Green Roofs

The Muse, Islington


During the late 1990s a group of nature conservationists and ecologists were actively in involved in a major regeneration programme in South-East London. The Creekside Regeneration Programme was a government-funded programme to rejuvenate an economically deprived area of Deptford in the London Borough’s of Lewisham and Greenwich. Part of the preparatory works, included an ecological assessment of the value of the area for wildlife. Although a run down post-industrial landscape the group discovered that, although not the most visually appealing landscape there were a number of interesting species, including one – the black redstart (Phoenicuros ochruros), which were of significant ecological value.

Although the use of green roof technology had been tentatively used in the 1970s and a number of innovators had tried to raise the profile of the technology through example projects and a book published by the London Ecology Unit [Building Green], the technology had remained relatively marginal.

However the work of the group in Deptford pushed developers and planners to consider the use of green roofs as mitigation for wildlife habitat, especially for the aforementioned bird. However, with little information on the value or the technical aspects of green roofs, the process was a hard task. Convincing the relevant professionals, architects, consultants and planners that this was both technically and an ecologically sound method of roofing was an uphill struggle. In effect the group were on a process of change, changing peoples habitats and assumptions and professional attitudes to vegetation on buildings. Fortunately in early 2000, the author contacted the Swiss Landscape Department, which lead to the first contact with Dr. Stephan Brenneisen and his innovative work on green roofs and biodiversity.

Thus was born the UK+CH green roof partnership. Although the Swiss regulatory process and attitude to green roofs was on a different level at the time, being one of proactive engagement, the Swiss experience has been a major influence on bringing green roofs into the mainstream in London and elsewhere in the UK. The relationship has been one of the major influences in transforming green roofs from a fringe sustainable technology to one that is now incorporated in both strategic policy in London, both at the regional and the local level. Although the agenda for green roofs as moved forward from an initial interest in biodiversity and nature conservation issues, to other themes, such as thermal performance, urban heat island amelioration and sustainable urban drainage, at its heart the provision of quality green roof habitat for rare invertebrates and birds still remains, and is still a major driver in terms of implementation.

The Black Redstart

Although relatively common on the continent and especially in Switzerland, this bird is at the northwesterly edge of its range in the UK. As it is a relatively recent addition to the UK bird fauna, it is vulnerable to competition from more established species, such as the Robin (Erithraca rubecula). With less than 100 pairs annually thought to breed in the UK, it is therefore protected under national wildlife legislation. It is relatively unique for a UK protected species as it is found in the main on industrial wastelands and in an urban context. It needs quite sparsely vegetated landscapes, similar to alpine scree slopes and plateaus.

In 1997 a group of ecologists found a number of pairs breeding along Deptford Creek. As the 3 pairs that were found in the area constitute more than 1% of the national population there was a degree of pressure, through planning regulation, to ensure development did not have a negative impact on the species. Wherever possible there is an obligation to ‘enhance or mitigate’ development plans for protected species. Thus was born a move to ensure that new developments catered for the black redstart One of the first projects to be impacted on was the Laban Dance Centre, designed Herzog de Meuron.

The ‘rubble’ roof was the first of many green roofs installed for black redstarts in London. Thirteen years ago this was a real milestone. But now, after much work, green roofs for biodiversity has become embedded.

However the nature conservationists involved in promoting green roofs, had very little knowledge or understanding of the how and the technical arguments to pressure developers to deliver habitat at roof level. Most of their thinking was intuitive. Furthermore many professional ecologists viewed the ‘idea’ as unfounded and lacking in any hard and fast data to back up the intuitive reasoning of group. The Swiss connection would change that providing a greater technical understanding of green roofs supported by detailed research.

The Ecological Context

Wasteland in the City of London

Whist the black redstart started was the starting point for a renaissance in interst in green roofs in London and increasingly across the rest of the UK, a further issue raised it’s head with the publication of a strategic white paper that set out the vision for development in the UK but which nature conservationists saw as having potentially negative impacts on a swathe of habitats, that, although post-industrial, had become important refuges for a whole swathe of rare and endangered species. In 2000 the UK Government published the Urban White Paper. In the context of this story, the white paper targeted the use of brownfield and post- industrial land as the primary source of land for new development. In London and also in the Thames Gateway Development region, large areas of old factories, dockyards, disused refineries, power stations and other land become the prime focus for economic regeneration. However at the same time, these rather ugly and untidy landscapes were increasingly being recognised by urban ecologists as some of the most important sites in the UK for rare invertebrates. Much of this fauna had once been prevalent in well-drained and low nutrient farmland that had since been improved. In general many post-industrial sites reflect this habitat characteristic. Thus over time much of the fauna and flora and had colonised these as they were left to nature. In fact one such site in South Essex, Canvey Wick, has been celebrated as ‘the Amazonian rainforest for rare invertebrates in the UK’. Thus was born a conflict between the needs for economic regeneration and an ecology once overlooked but of national importance. At the time of writing a number of other similar sites have become the focus of concern from conservationists, notably the Isle of Grain lorry park .

The Laban Dance Centre rubble roof

Climate Change – a shift in emphasis

During the mid 2000s there was a distinct policy shift as the climate change agenda became more prevalent Where the London Mayor had previously been concerned with ‘fuel’ poverty a series of extreme hot summers shifted the emphasis to also include concerns regarding ‘cool’ poverty and the likely impacts of increased summer temperatures and the negative effects of the Urban Heat Island. The London Climate Change Partnership stated in 2002 that ‘Summers by 2050 will be 1.5 – 3.5 0 C hotter…in central London the urban heat island currently adds 5 -6 0 C to summer night time temperatures and will intensify in the future’ .

Thus green roofs were seen to be a potentially cross cutting technology and multi-beneficial solution that could help the capital meet the challenges of climate change and help the city adapt to the likelihood of higher summer temperatures and increases in intense summers storms [leading to localized flash floods]. These fears have been realized to a certain extent with the exceptionally hot summers of 2005 and 2006 and extensive flash flooding of 2007.

However London has both a central strategic authority [the Greater London Authority] and also 32 local boroughs [LB] with responsibility for their area. A number of these boroughs, notably City of London, Islington, Lewisham and Tower Hamlets, were actively promoting and ensuring that green roofs were installed for nature conservation.

The New London Plan

In 2007 the author, along with colleagues, was commissioned to write a technical review of green roofs and green walls. This report was to support the change in policy on green roofs from one of ‘encouragement’ to expectation’. The report reviewed all the technical data available for a range of benefits including reduction in the urban heat island, thermal performance, storm water attenuation, biodiversity and amenity. It also reviewed city policies elsewhere in the world. The technical report, published in late 2007, lead to a distinct policy on Living roofs and walls in the revised London Plan published in March 2008.

The Mayor will and the boroughs should expect all major developments to in corporate living roofs and walls, where feasible and reflect this in Local Development Framework policies. It is expected that this will include roof and wall planting that delivers as many of these objectives as possible:

Accessible roof space

Adapting and mitigating for climate change

Sustainable urban drainage

Enhancing biodiversity

Improved appearance

Boroughs should also encourage the use of living roofs in smaller developments and extensions where the opportunity arises

Although it is too early to see what the effect of the new policy, green roofs have been delivered on an increasing scale in the capital over the last 8 years and the new Plan should lead to an increase in delivery.

Londons Green Roof Policy

A London Audit undertook an audit of green roofs in London in 2004. The total area of green roofs was no doubt underestimated due to the challenges of accessing information from architects, developers and companies. The audit estimated that 76,682m 2 of green roofs had been installed in the Greater London area. Some of these roofs dated back to 1932! In 2008 an further audit was undertaken to assess the amount of green roofs installed between January 2004 and December 2008. This used data provided by a number of green roof companies active in the UK and is estimated that the figures provided represent 80% of the roofs installed during that period. Over 420,00m 2 were installed by the companies suggesting that near to 500,000m 2 were actually installed – equivalent to twice the size of Hyde Park and Kensington Gardens combined.

It is important to note that the majority of this green roofs were installed in the central core of the city. Furthermore as the table below highlights that the area with the largest percentage of installed green roofs was the London Borough of Islington. This borough had actively promoted the use of green roofs through it’s planning department. Thus demonstrating that urban planning departments that embrace and promote these activities can have immediate effect in the implementation of green roofs.

This area of green roofs installed between 2004 and 2008 was prior to the publication of the New London Plan and the positive effect of this strategic planning policy on green roof implementation is yet to be assessed but is likely to augment the delivery of green roofs on new developments in the Capital.

A Green Roof Toolkit

Although London now has a distinct policy on green roofs and a large number of green roofs have been installed, there has been limited guidance on how green roofs should be installed in London.

The Environment Agency, a key statutory consultee on new developments, is responsible for flood defense and rivers. Its remit covers both flooding, climate change and biodiversity. In 2008, the Thames region of the Environment Agency commissioned the author to provide a detailed toolkit to guide developers to what the Agency expected green roofs to provide and how. Importantly this work also managed to persuade engineers within the Agency to accept that green roofs do provide significant benefits as a source control mechanism in the sustainable urban drainage train.

Greening Existing Building Stock

With the new London Policy and activities by the 32 LBs, the argument for green roofs on new developments looks positive in the London area. However one of the key concerns for the London Climate Change Partnership [LCCP] is the need to adapt existing buildings to the challenges of climate change. Reduction of the Urban Heat Island is an important element and, as has been recognized elsewhere, there is a need for a 10% increase in urban green spaces in UK cities to combat climate change. In London, especially in the central activity zone [CAZ] where space is limited and the effects of the Urban Heat Island are most pronounced, roofs will be a very important in delivering green space.

The Need to Retrofit

The implementation of green roofs in new developments within London is now a mainstream ecological construction method as has been outlined above. However it is also recognized that there is a need to retrofit green roofs on the existing building stock. Especially in CAZ. The report published in 2008 by the London Government estimates that 325 of the land area of Central London consists of roofs that could be retrofit with green roofs in the future without additional structural work to facilitate such an approach. Therefore the area of roofs within 6km circle centred on Trafalgar Square that could be greened would constitute a total area of 10 million m 2 .

The burning issue for planners is how to achieve wholescale retrofitting of green roofs on existing buildings. The London Government commissioned a report, Economic incentive schemes for retrofitting London’s existing homes for climate change impacts’, which outlines this how this might be achieved interms of incentives and the monies that would be needed to achieve. The report also provided detailed figures on how much such a programme would cost and would the environmental benefits that would be provide:

‘A scheme for four inner city areas — Cannon Street, Oxford Street, Tottenham Court Road and Canary Wharf – with a green roof area of 226,750m2 would cost around £4 million and provide environmental benefits17 worth £4 million.

A wider scheme covering the City of London, part of the London Borough of Hackney, part of the London Borough of Tower Hamlets and part of the

A scheme in the West End with a green roof area of 3.2 million m2 would cost around £55.5 million and provide environmental benefits worth £55.5 million. ‘

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