Why green roofs are winning

'Green Roofs' was held at SCI, 14/15 Belgrave Square, London SW1X 8PS on 29 April 2010 at 17.30, by the Construction Materials and Horticulture Groups.

This 'green' event included two key speakers, Lionel Shearman (Director of Safeguard Europe) and Matthew Hoddinott (Technical Director of Cityroofs). It attracted a large audience of 87 persons for a very interesting discourse on the increasingly topical subject of 'Green Roofs'.

Lionel Shearman, a Director of Safeguard Europe and a specialist in below ground structural waterproofing, was the principal speaker. Lionel discussed the benefits of green roofs and the driving forces behind their increasing popularity. This has involved looking at the different types of green roofing to assist the specifiers in choosing the roofs that most accurately meet their design criteria. Methods of construction and layer build-up for flat green roofs as well as for Scandinavian-style pitched green roofs were mentioned. Green roofs can be particularly useful for schools, hospitals and underground car parks, since they reduce thermal expansion and contraction of membranes. The drainage systems can act as useful reservoirs of rainwater and reduce the risk of flooding. Performance depends upon substrate type and depth. Lionel also gave examples of various planting options, including self-colonising 'brown' (or 'biodiverse') roofs.

The local environment for green roofs can embrace the following:

  • Habitat for wild life
  • Improved air quality through reducing CO2
  • Moderates the urban 'heat island effect'
  • Filters pollutants from rainwater
  • Increases biodiversity, especially in creating new wildlife habitats.

Green roofs can aid planning applications for new buildings. Thermal benefits promote keeping buildings cool in summer and warm in winter, with overall insulation depending upon both saturation of the roof and the ventilation involved.

Site suitability is a key factor when choosing a particular green roof system:

  • Considerations for rainfall patterns
  • Likelihood of extreme temperatures
  • Presence of salt air in coastal areas
  • Exposure to the sun and other climatic conditions.

Horticulturists & designers need to be increasingly consulted in green roofing matters, particularly in areas of access and safety:

  • Annual inspection and maintenance
  • Access for roof gardens
  • Dimensions and pitch of the green roofs for drainage and ventilation conduits.

The second speaker was Matthew Hoddinott, Technical Director of Cityroofs, who is involved with green roofing in the UK and Ireland. His talk has complemented that of Lionel Shearman on creating living roofs. Matthew, discussed the possibilities for green roofs to improve the social climate and thus make a useful contribution to a better environment. Better use should be made of our existing and future assets with imaginative solutions that respond to everyday needs of space, sunlight and access to open space.

There is a need to promote further photosynthesis within the plants used in green roofing, so as to convert more CO2 into oxygen. Matthew has considered the design implications of urban greening, rainwater harvesting and the whole life-cost of changing roof space into innovative usage. Such innovation includes parking spaces, harnessing natural resources and, importantly, provision of water management.

There were plenty of lively questions, comments and discussions from the large audience present, which is a good indicator of the overall high success that this particular 'green' event generated. Appreciation was shown to the Meeting Organiser, John Fifield of the Construction Materials Group, who also actively involved the SCI Horticulture Group, and to the SCI staff involved in the well-coordinated facilitation of this event.

Prof John Bensted, Chair of SCI Construction Materials Group

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