The Benefits of Green Roofs and Living Walls

Green roofs and living walls provide a number of private and public benefits that reduce the impact of urbanization and contribute to the sustainability of ecosystem services and energy conservation in large cities around the world. 

Depending on the plants and depth of growing medium, these benefits can include: 

1. Decreasing Storm Water Runoff

Capable of retaining 60 to 100% of water during a rain event

2. Improving Thermal Performance

Heat flow through the roofing system is reduced by 70-90% in the summer and 10-30% in the winter. 

3. Increasing Sound Insulation, And Protection of the Roof Membranes

Vegetation, growth medium, and trapped air can increase the effectiveness of building sound insulation by absorbing or reflecting sound frequencies.

4. Increasing Aesthetics, Public Relations and Recreational Green Space

Are an easy and effective way of beautifying the built environment, increasing aesthetic value and functionality. The sight, sounds, smells, colors, and movement of plants contribute considerably to human health and well being[1], reducing stress and elicits a relaxed state of mind[2] 

5. Reducing the Urban Heat Island Effect (UHI)

Vegetation mitigates the UHI but by warming the air less; vegetation reflects solar radiation that would otherwise be absorbed by roof surfaces.  If only 6% of Toronto’s roofs were covered with a green roof would reduce regional energy demand by up to 5-10%, saving more than $1 million in annual energy costs[3]  

6. Improving Air Quality and Reducing Airborne Particulates

Green plants capture airborne pollution in two ways: absorption or by adhering to the leaf or stem surface. Green roofs and living walls can complement, and in some cases, almost equal the capacity of removing pollutants as existing trees. Increasing soil depth and plant coverage influence the amount of CO2 and other airborne particulates captured; intensive green roofs reduce pollution more than extensive green roofs. 

7. Sustaining Biodiversity

Urban wildlife and insects use and inhabit Green Roofs and Living Walls in the urban landscape; promoting important ecological functions such as pollination, decomposition, and pest control.

[1] Peck, S. W., Callaghan, C., Kuhn, M. E., and Bass, B. (1999). Greenbacks from green roofs: forging a new industry in Canada. Canada Mortgage and Housing Corporation, Ottawa, ON.

[2] Ulrich, R. S., and Parsons, R. (1992). Influences of Passive Experiences with Plants on Individual Well-being and Health. In: The Role of Horticulture in Human Well-being and Social Development. Timber Press Inc

[3] Dunnett, N., and Kingsbury, N. (2004). Planting green roofs and living walls. Timber Press, Portland, OR.