Carbon isoc green roofs good practice guide

www.islington.gov.uk

Green roofs and walls Good Practice Guide 1

Green roofs and walls Good Practice Guide 1

What are green roofs and walls and what benefits do they offer?

Did you know?

Islington Council strongly encourages green roofs – it gave planning permission to over 7,120 square metres of them between April 2008 and March 2009.

Green roofs and walls are simply roofs or walls that have been intentionally covered, in whole or in part, in vegetation. Green roofs (sometimes also referred to as brown or living roofs) and green walls can be incorporated onto both new and existing buildings. They provide a range of benefits, for example by supporting biodiversity, reducing rainwater run-off, increasing energy efficiency and providing local cooling. These benefits are described further below.

The importance of green roofs and walls is now increasingly recognised in the UK, including through planning policy. For example the recent update to the London Plan included a policy requiring major developments to incorporate ‘living roofs’ wherever feasible.

Green roofs and walls provide valuable wildlife habitats and can significantly enhance biodiversity. They can support a variety of plants as well as providing nesting and foraging habitats for invertebrates, butterflies and birds. Green roofs and walls are particularly important in urban areas, providing valuable habitats in built up areas that are often lacking in biodiversity. They can also play a useful role in connecting existing areas of habitat and supporting rare and protected species. Green roofs provide different habitats to trees and gardens and therefore do not compensate directly for their loss. However roofs can be used to create a range of complementary habitats and are particularly effective in combination with other biodiversity enhancements such as provision of artificial nesting and roosting sites and ecological landscaping (see Good Practice Guide 4).

Figure 1: Biodiversity based green roof on the Muse, Newington Green © Bere: Architects

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Green roofs and walls Good Practice Guide 1

In addition to the important biodiversity benefits of green walls and roofs, other benefits of green roofs/walls include: • Aesthetic and amenity value – through incorporation of colourful foliage, flowering plants or accessible amenity areas. However, provision of amenity space (e.g. for food production and relaxation) on green roofs must be balanced against provision of space for wildlife.

• Sustainable drainage - green roofs can form a key part of SUDS (see Good Practice Guide 2). They reduce the quantity of runoff by holding water and encouraging its release through evaporation. They also improve the quality of run-off by filtering contaminants.

• Thermal efficiency/insulation – green roofs and, to a lesser extent green walls, can help to insulate buildings, reducing energy demand and associated carbon emissions.

• Reducing the 'urban heat island' effect - providing green roof and wall cover can help to lower surface temperatures and cool dense urban areas.

• Managing air quality – vegetation on roofs and walls can help to improve air quality through absorption of carbon dioxide, some air pollutants and dust.

• Reduce noise levels – green walls and roofs can help to dampen noise levels.

• Cost savings - green roofs and walls can increase the life expectancy of a roof or wall by protecting the building fabric from temperature variations, UV radiation and other climatic factors. The other benefits described here can also provide further cost savings.

• Enhanced sales or rental value - green roofs and walls may enhance the sale or rental value of a development by increasing the aesthetic appeal of a property, reducing energy costs and demonstrating sustainable design and social responsibility.

How is a green roof structured?

Planting Level System substrate

Green roofs should incorporate a number of layers, as shown opposite: • Substrate - provides a low weight growing medium (e.g. crushed brick)

Filter membrane

• Filter membrane – prevents soil being washed into the drainage layer

Drainage element

• Drainage element – holds some rainwater, while allowing the excess to drain away, preventing water logging

Moisture mat Roof barrier and waterproofing

• Moisture mat – retains water and helps prevent the roof drying out; also protects the waterproofing layer • Root barrier and waterproofing – protects the roof from water or root damage

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Green roofs and walls Good Practice Guide 1

What types of green roofs and walls are particularly suitable for Islington?

Green roofs Green roofs can be fitted to any roof that is flat or gently sloping. A variety of types of green roofs exist, varying from extensive to intensive types, depending on the depth of substrate and the type of plants that are supported.

The main types of green roof are: • Intensive roofs – these roofs are designed to allow access for people.

They are likely to have deep substrates that can support trees and shrubs, as well as providing accessible areas. These roofs require higher levels of maintenance.

• Extensive roofs – incorporate lightweight substrates which support a range of species. They range from shallow sedum mats, which do not offer significant biodiversity or water holding benefits, to deeper substrates which can support valuable habitats, such as that shown in figure 2.

Figure 2: Laban Dance Centre, Deptford. Source: livingroofs.org

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Green roofs and walls Good Practice Guide 1

Did you know?

Green roofs and photovoltaic (PV) panels can be mutually beneficial. Green roofs create a microclimate that enhances the operating efficiency of PV panels, while the panels can help to create greater habitat diversity on the roof.

Islington Council’s preferred specification is a biodiversity-based extensive substrate green roof with a substrate (growing medium) depth of 80150mm. These roofs support a greater range of plant species and in turn wildlife species, and have greater water holding benefits (green roofs can attenuate up to 60% of runoff). These benefits are particularly important for Islington because the borough generally lacks space for biodiversity and much of the land area is hard-surfaced, leading to high levels of run-off which increases flood risk. The variety of life supported by a green roof can be further increased by varying the depth and type of substrate, using other features such as logs, rocks or areas of bare sand/shingle and ensuring that the roof is planted with a high proportion of native herbs and wildflowers of significant ecological value.

Biodiversity roofs can also be combined with accessible areas to create attractive, low maintenance amenity spaces. The below image shows a mixed biodiversity based and accessible roof space on an office building in Islington which provides an attractive outdoor amenity area for employees.

Figure 3: Accessible green roof on a new office development, Ropemaker, Islington

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Green roofs and walls Good Practice Guide 1

As well as designing green roofs as a part of new buildings, it is also possible to retrofit green roofs to existing buildings. The below image shows a biodiversity-based extensive substrate green roof which has been retrofitted to Islington Council’s offices at 222 Upper Street.

It is important that green roofs form an integral part of the design of new buildings and are designed in from an early stage because the increased loading associated with thicker substrates may have implications for structural design. Loadings will vary for different types of green roof, for example starting at 80-150kg/m2 for extensive substrate based roofs. Indicative structural loadings for different types of roofs can be found in the London Living Roofs Technical Guide. Locational factors such as shading from surrounding trees should also be considered at the start of the design process to ensure the roof specification and planting schedule are appropriate to the context and any related management requirements are considered.

Figure 4: Retrofitted green roof at Islington Council Municipal Offices

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Green roofs and walls Good Practice Guide 1

Green walls Green walls generally involve the use of climbing plants to create a living cladding system. The two principle types are: • Climbing wall plants – these can grow directly on a wall (especially those of brick and stone where the porous surface allows them to attach more easily) or be supported by trellises or steel cables against a wall. Commonly used species for wall-greening are ivy, Russian-vine and Virginia-creeper. • Container systems - here, plants are grown in large irrigated containers at height which allow them to grow/hang down.

While simple green walls using climbing plants have been widely used for centuries, more extensive green wall systems are developing all the time.

Innovative systems now available include walls constructed from trays of plants that have been pre-grown off-site and slotted together on a steel frame, then connected up to an internal irrigation system.

The most suitable approach to creating a green wall for any particular development or site is likely to depend on the prioritisation of functions it is intended to perform (e.g. biodiversity, amenity, sound insulation) and the possibilities that the specific space affords. For further details on the variety of green wall systems and design options available and what might be most suitable for your situation you are advised to contact green wall specialists (see contact details at end of document).

Figure 4: Green wall, Madrid

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Green roofs and walls Good Practice Guide 1

Case study: Paradise Park Children’s Centre – green wall and roof Paradise Park Children's Centre is set within an existing park. Its green wall - the biggest on a public building in the UK - runs the full length of the front façade of the building and is planted with a range of herbaceous plants including Heuchara, Valerian, Euphorbia, Ajuga and Geranium. The green wall and a green biodiversity based substrate/‘rubble’ roof provide wildlife habitats which complement the surrounding park, as well as providing aesthetic and cooling benefits. Recycled rainwater is used to irrigate the green wall, helping to keep management costs down and reduce mains water demand.

Further information For further information including details of green roof suppliers and installers the following websites are useful starting points: • Independent resource on green roofs founded by Dusty Gedge http://livingroofs.org/ • Similar resource founded by University of Sheffield and Groundwork Sheffield www.thegreenroofcentre.co.uk • GLA technical report on living roofs and walls www.london.gov.uk/mayor/strategies/sds/docs/living-roofs.pdf Note: These guidance notes are advisory only and not Supplementary Planning Documents.

However following their advice will help developments satisfy various policies contained within the London Plan and meet wider sustainability objectives.

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www.islington.gov.uk

Green roofs and walls Good Practice Guide Green roofs and walls can provide a range of benefits for new and refurbished developments, including for biodiversity, drainage and energy use. This note provides good practice guidance on the types of green roofs and walls which are most suitable in Islington, alongside a range of examples of where such roofs and walls have been successfully installed.

This Good Practice Guide is part of a set of notes providing information on sustainable design for planners, developers and interested residents or businesses. The set includes guidance on the following: • Good Practice Guide 1: Green Roofs and Walls • Good Practice Guide 2: Sustainable Drainage Systems • Good Practice Guide 3: Climate Change Adaptation • Good Practice Guide 4: Biodiversity in the Built Environment

If you would like this document in large print or Braille, audiotape or in another language, please contact 020 7527 2000.

Contact Islington 222 Upper Street, London N1 1XR E contact@islington.gov.uk T 020 7527 2000 F 020 7527 5001 Minicom 020 7527 1900 W www.islington.gov.uk