Friday, 2 November 2012

Green Roof Tops could become the next green innovation for Smart Cities of the future.

Photograph By Diane Cooke and Len Jenshel
I recently came across a fantastic idea that apparently has been around for some time. Jean O'Dwyer on her popular Facebook page called The Earth Story explains the concept far better than I could possibly hope to: 

The concept of the green roof is not a new phenomenon; with its basic functionality being utilised for several centuries. A green roof (also known as an eco-roof, nature roof, living roof or roof greening system) is a living, vegetative system that contains a substrate (growing media) and a vegetation layer at its outermost surface. Green roof systems can be used as a way of compensating for the increase of impervious surfaces, providing a visual and recreational escape from the ‘concrete jungles’ of urban landscapes.

One of the most attractive qualities of green roofs is that they wholly encompass the idea of sustainability. Sustainability can be broadly defined as an attempt to provide the best outcomes for the human and natural world both now and into the indefinite future. It relates to the continuity of economic, social and environmental aspects of human society, as well as the non-human environment.

Green roofs offer advantages socially, economically and environmentally which are all necessary to fully achieve any step towards sustainable development.

Environmental Benefits: 
  • Storm-water management   -  Retrofitting a green roof system on a pre-existing rooftop can become an onsite water retention facility. Depending on the rain intensity and the soil depths runoff can be reduced by 15 to 90 %.
  • Reduction of the urban heat Island effect -  Concrete and asphalt structures absorb the ultraviolet radiation from the sun during the day. At night however, this radiation is released as thermal infrared radiation which creates a dome of higher temperatures over cities. Because green roofs store water in the growing media and plants, latent heat loss is accomplished via transpiration from plants and evaporation of moisture from the growing medium collectively referred to as evapo-transpiration.
  • Reduction of air pollution -  Plants can reduce the concentration of airborne pollutants in a number of ways. The leaves of the plant fix particulates, and then when it rains the particulates are washed down into the soil substrate where they become trapped in the soil substrate or growing medium. Through plant photosynthesis and respiration air containing carbon dioxide and toxins is absorbed through the stomata and transformed into glucose and water. Airborne particulates become trapped on the plant foliage until it rains. The particulates are then washed into the soil substrate and become entrained in the substrate mix preventing the dusts being dispersed downwind.
  • Promotes Biodiversity - Green roof offer habitat patches in areas which otherwise would be void of ecosystem services. Even in densely populated areas green roofs can attract a range of beneficial species of birds, bee’s, butterflies and other insects. The fact that the habitats are created at a height is actually beneficial, particularly to species that do not interact with human beings. By creating new habitats for plants and animals valuable ecosystem services can be reinstated into urban areas.
Economic Benefits:
  • Prolonging the existing roofs life - The average life span of a conventional roof is only 20 years attributed to damage and stress from cooling, heating and exposure. If a green roof system is incorporated into design the temperatures do not get too high due to evaporative cooling and frost damage to the roof structure is avoided as the soil takes the worst of it. It is estimated that the installation of a green roof can double or even triple the life span of a roof, hence reducing maintenance costs significantly for a small by comparison initial investment.
  • Reduction in Energy Costs - Accredited to the natural thermal insulating properties of vegetative cover green roofs discourage heat build-up. This results in a decreased need for air conditioning in the summer and heating in the winter. It is estimated that a one story building can save anywhere between 20 and 30% of electrical energy requirements with the addition of a green roof. 
Social Benefits:
  • Green roofs can help to visually ease the stress created by a lack of green space in urban communities. By intertwining culture and nature, we can actively design to regenerate human and ecological health. 
As a whole, the need to divorce our relationship with consumerism and resource use is of utmost importance and the relationship between humanity and nature must be rekindled. Green roofs are not only a tool towards environmental sustainability, but can act as a visual reminder of the importance of nature in our lives!

Jean O'Dwyer, The Earth Story

Well there we have it and what an amazing and innovative development to aid energy efficiency in the world's built environment and hopefully, something that will catch on and become a major contributor in the energy efficient mix for sustainable Smart City developments of the future.