Green roofs evolve around the idea of generating a green space such as a garden on the roof of a building. We live in an ever increasing urbanised world with the UN estimating that by 2030 there could be as many as 5 billion people living in urban areas [1]. The creation of a green space on a roof top helps to mitigate against the environmental problems that increased urbanisation generates [2]
What is a green roof?
Broadly speaking, there are two main types of green roofs; an extensive green roof and an intensive green roof. The main difference between the two types is the depth of the growing medium. An extensive roof has a much shallower growing medium and therefore can only support smaller plants [3]. However, this means that extensive green roofs can be implemented on existing roofs without any major structural change and therefore are generally cheaper and easier to implement.
Benefits of a Green Roof [4]
- Reduce buildings’ energy consumption
- Lower a building’s carbon footprint
- Reduce urban heat-island effect
- Increase sound insulation
- Act as fire resistance
- Increase longevity of the roof membrane
- Mitigate storm-water run-off from building surfaces
- Provide habitat for wildlife
- Improve air quality
While there is an initial cost of implementing a green roof, they are argued to bring about many benefits which in the long term are costs-effective, such as reducing a building’s energy consumption. Therefore green roofs would appear to be a viable way to reduce costs and the negative environmental impact that buildings have on the environment, as well as an aesthetic appeal if they are well designed.
National Policy
In the UK, there is no policy that stipulates that green roofs have to be implemented into developments, however national policies such as ‘Securing the Future’ the government’s sustainable development strategy, supports the use of green roofs [5]. The UK appears to be lagging behind other countries in implementing policy on green roofs. For example, in Brazil and Switzerland there is legislation that states “all new and renovated flat roofed buildings must have a green roof installed” [6]. It may not be long till the UK follows a similar line; therefore implementing green roofs now will help to give businesses and individuals a head start. It is also another means of appealing to the ever more environmentally conscious public.
[1] UNIS (2010).
[2] Lundholm and Peck (2008)
[3] Kosareo, L. and Ries, R. (2007) Comparative environmental life cycle assessment of green roofs. Building and Environment
[4] Oberndorfer, E., Lundholm, J., Bass, B., Coffman, R., Doshi, H., Dunnett, N., Gaffin, S., Kohler, M., Liu, K. and Rowe, B. (2007) Green Roofs as Urban Ecosystems: Ecological Structures, Functions, and Services. BioScience, 57, (10), 823-834
[5] www.environment-agency.gov.uk/
[6] 4Ecotips (2010) www.4ecotips.com
