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Sustainability

Green Roofs can help change the way we live

Policy

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The urban landscape is rapidly changing. As the pressure for new housing in our ever-expanding cities mounts, our ‘green’ spaces are being lost at an alarming rate. Sustainable design in regeneration policies is vital in order to conserve or relocate these important habitats.

Policies are slowly being introduced in major cities, such as London and Sheffield, which recognise the need for green space regeneration but include details on how and where these spaces should be recreated. They highlight the role that green roofs should play in this regeneration and describe all their associated benefits.

Here are some of the latest developments

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Greening The BIDs

Urban greening and green infrastructure are cost-effective ways of increasing environmental and economic resilience to ensure London remains a great city in which to live, work and invest. Urban greening measures can help reduce the urban heat island effect and surface water flooding, as well as improve the experience of the urban environment for residents, businesses and wildlife.

In order to catalyse urban greening in central London, the Greater London Authority has funded green infrastructure audits to identify opportunities for increasing green cover in 10 central London Business Improvement Districts (BIDs) or employer groups. Reports for participating BIDs and employer groups are listed at the bottom of the page.

In total around 500 hectares have been audited, which identified the potential for 300 rain gardens, 200 green walls and over 100 hectares of green roofs, as well as other small scale interventions such as planters and window boxes.

Strategy Documents

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Reducing Energy Costs

ODPM (2006) Approved Document L2a & L2b – To reduce energy consumption in buildings by 25% (vs ADL 2002) The Energy White Paper (2007) – 10% of UK Electricity to be from renewable sources by 2010 & 20% by 2020

Explanation

The thermal benefits of a green roof mean that during the summer months the green roof keeps the roof cool. This not only keeps the temperature inside the building down but it also keeps the temperature at roof level down making solar panels work at their most efficient rate. Whilst these benefits are not be included in ‘U’ value calculations, numerous studies have outlined the energy reductions, with a very conservative estimate being 11.25kWh/m2/year.

Green roofs actually keep the roof level in summer months between 20-28 degrees centigrade. 25 degrees centigrade is the optimum temperature for a solar panel and any increase above thirty degrees the solar panel loses half a percent of efficiency every degree.

Carbon Emmissions

Kyoto Protocol – 60% reduction by 2050 (vs 1990)
BERR (2008) Strategy for Sustainable – 26% reduction by 2020 (vs 1990)

A green roof reduces the carbon dioxide in the air. Photosynthesis is a process plants use to make energy for themselves. During photosynthesis plants take in carbon dioxide and release oxygen into the air.

A 1000 m2 of green roof can absorb 5 tonnes of carbon emissions a year, every year after the day after the green roof is installed.

SUDS

Sustainable Urban Drainage

DEFRA (2008) Government Strategy for Water (Vision 2030) – Land increasingly flexibly managed for flood storage.

DEFRA (2008) Government Strategy for Water (Vision 2030) – Large majority of water bodies having good ecological & chemical status and Healthy rivers, lakes, estuaries, coasts & groundwaters.

UK Framework Indicators – Indicator 31 – reduce no. of properties at risk of flooding
EU Water Framework Directive 2000/60/EC – All surface water and groundwater to be classified as “good status” by 2015.

DEFRA (2002) A Biodiversity Strategy for England – Biological quality of rivers in England (Indicator H7) Nutrient levels in rivers & lakes (W5).

Green roofs hold up to 87% of rainwater and slowly release the water back into the drainage systems. Slowing down the rate the drains are getting filled takes a great pressure of the drainage systems. A green roof also filters harmful chemicals from rainwater.
The UK pays out £1.9 billion a year to fix properties effected by floods.

Bio-Diversity

UN World Summit on Sustainable Development (2002) – Significant reduction in rate of biodiversity loss by 2010

Habitats Directive – 92/43/EEC – To ensure the restoration / maintenance of natural habitats

Convention on the Conservation of Migratory Species of Wild Animals (Bonn Convention / CMS – To conserve / restore habitats where migratory wild species live).

DEFRA (2002) A Biodiversity Strategy for England – Develop Action Plans relevant to urban areas that facilitate:

  • HABITATS: Lowland heaths; Wood pastures; Parklands
  • SPECIES: stag beetle, song thrush & bats

Convention on the Conservation of European Wildlife & Natural Habitats – 82/72/EEC – To protect 500+ plants and 1,000+ animal species

Green roofs create habitats for rare invertebrates and insects. Birds use the roofs as a stepping-stone for birds across built – up cities. There have been huge ranges of species of plants and, bees and invertebrates found on green roofs.