Energy Conservation Potential of an Extensive Green Roof in Iran for One Year Duration

Document Type: Original Article

Authors

1 PhD Student, Department of Horticultural Science and Landscape, Ferdowsi University of Mashhad, Iran

2 Professor, Department of Horticultural Science and Landscape, Ferdowsi University of Mashhad, Iran

3 Assistant professor, Department of Horticultural Science and landscape, Ferdowsi University of Mashhad, Iran

Abstract

The temperature of cities continues to increase because of the heat island phenomenon and the undeniable climatic change. The observed high ambient temperatures intensify energy problems in cities, deteriorates comfort conditions, put in danger the vulnerable population and amplify the pollution problems. There are some suggested ways to reduce these issues, among them vegetated roofs are shown to be promising. This study describes energy consumption performance of an extensive modular type green roof with different plant selections using a randomized complete design in Mashhad, Iran. Nine species from three major taxonomic and functional plant groups (grasses, ground covers and sedums) namely (Agropyron cristatum, Festuca aurundinacea, Festuca ovina, Potentilla sp., Frankenia thymifolia, Vinca minor, Sedum acre, Sedum spectabile, Carpoboratus edulis) were selected. Temperature fluctuations during four seasons were recorded with three replicates. Experimental trials with growing beds without plants (bare roofs) were also used as controls. Small hand manual thermometers were placed in each module (box) and air temperature was also recorded. The results showed very significant temperature differences between the green and bare roof modules. Larger plants with higher biomasses kept temperatures more stable. Thermal comfort and energy saving was achieved using green roofs in this research and it could be well used in a large scale for growing cities and population energy requirements.
 

Highlights

Significant differences were observed between green and bare roof energy conservation potential considering temperature.

Larger plants and higher biomass kept temperatures more stable in both warm and cold seasons.

Thermal comfort and energy saving can be maintained with application of green roofs in a large scale for growing cities and population energy requirements.

The presence of plants in green roofs on top of a building showed major beneficial temperature reduction and subsequently energy saving.

 

Keywords


Akbari, H., Davis, S., Dorsano, S., Huang, J. and Winert, S. 1992. Cooling our communitie – a guidebook on tree planting and light colored surfacing. US Environmental Protection Agency, Office of Policy Analysis, Climate Change Division, January.

Akbari, H. and Konopacki, S. 2004. Energy effects of heat-island reduction strategies in Toronto, Canada. Energy and Buildings, 29: 191–210.

Akbari, H., Levinson, R. and Rainer, L. 2005. Monitoring the energy-use effects of cool roofs on California commercial buildings. Energy and Buildings, 37: 1007–1101.

Alexandri, E. and Jones, P. 2008. Temperature decreases in an urban canyon due to green walls and green roofs in diverse climates. Building and Environment, 43: 480–493.

Bahgat, G. 2010. Israel’s energy security: The Caspian Sea and the Middle East. Israel Affairs, 16: 406–15.

Cartalis, C., Synodinou, A., Proedrou, M., Tsangrasoulis, A. and Santamouris, M. 2001. Modifications in energy demand in urban areas as a result of climate changes: An assessment for the Southeast Mediterranean region. Energy Conversion and Management, 42 (14): 1647–1656.

Castleton, H.F., Stovin, V., Beck, S.B.M. and Davison, J.B. 2010. Green roofs; building energy savings and the potential for retrofit. Energy and Buildings, 42: 1582–91.

Dunnett, N. and Kingsbury, N. 2008. Planting green roofs and living walls, 2nd edition. Timber Press, Portland Oregon. 

Dvorak, B. and Volder, A. 2010. Green roof vegetation for North American ecoregions: A literature review. Landscape and Urban Planning, 96: 197–213.

English Nature. 2003. Green roofs: Their existing status and potential for conserving biodiversity in urban areas. English Nature Report No. 498. English Nature, Peterborough.

Eumorfopoulou, E. and Aravantinos, D. 1998. The contribution of a planted roof to the thermal protection of buildings in Greece. Energy Buildings, 27: 29–36.

Getter, K.L., Bradley Rowe, D. and Cregg, B.M. 2009. Solar radiation intensity influences extensive green roof plant communities. Urban Forestry & Urban Greening; 8: 269–81.

Gill, S.E., Handley, J.F., Ennos, A.R. and Pauleit, S. 2007. Adapting cities for climate change: The role of green infrastructure. Built Environment, 33: 115–133.

Hassid, S., Santamouris, M., Papanikolaou, M., Linardi, A., Klitsikas, N., Georgakis, C. and Assimakopoulos, D.N. 2000. The effect of the Athens heat island on air conditioning load. Energy and Buildings, 32: 131–141.

Jaffal, I., Ouldboukhitine, S.E. and Belarbi, R. 2012. A comprehensive study of the impact of green roofs on building energy performance. Renewable Energy, 43: 157–164.

Kolokotroni, M., Ren, X., Davies, M. and Mavrogianni, A. 2012. London’s urban heat island: Impact on current and future energy consumption in office buildings. Energy and Buildings, 47: 302–311.

Kumar, R. and Kaushik, S.C. 2005. Performance evaluation of green roof and shading for thermal protection of buildings. Building and Environment, 40 (11): 1505–1511.

Levermore, G. 2008. A review of the IPCC assessment report four, Part 1: the IPCC process and greenhouse gas emission trends from buildings worldwide. Building Services Engineering Research and Technology, 32: 349–61.

Liu, K. and Minor, J. 2005. Performance evaluation of an extensive green roof. Toronto: National Research Council of Canada.

Permpituck, S. and Namprakai, P. 2012. The energy consumption performance of roof lawn gardens in Thailand. Renewable Energy, 40: 98-103.

Santamouris, M., Papanikolaou, N., Livada, I., Koronakis, I., Georgakis, C., Argiriou, A. and Assimakopoulos, D.N. 2001. On the impact of urban climate to the energy consumption of buildings. Solar Energy, 70 (3): 201–216.

Santamouris, M., Pavlou, C., Doukas, P., Mihalakakou, G., Synnefa, A., Hatzibiros, A. and Patargias, P. 2007. Investigating and analysing the energy and environmental performance of an experimental green roof system installed in a nursery school building in Athens, Greece. Energy, 32 (9): 1781–1788.

Sfakianaki Pagalou, E., Pavlou, K., Santamouris, M. and Assimakopoulos, M.N. 2009.  Theoretical and experimental analysis of the thermal behaviour of a green roof system installed in two residential buildings in Athens, Greece. International Journal of Energy Research, 33 (12): 1059–1069.

Shashua-Bar, L., Potchter, O., Bitan, A., Boltansky, D. and Yaakov, Y. 2009. Microclimate modelling of street tree species effects within the varied urban morphology in the Mediterranean city of Tel Aviv, Israel. International Journal of Climatology, 30: 44–57.

Solomon, B.D. and Krishna, K. 2011. The coming sustainable energy transition: History, strategies, and outlook. Energy Policy, 39: 7422–31.

Spala, A., Bagiorgas, H.S., Assimakopoulos, M.N., Kalavrouziotis, J., Matthopoulos, D. and Mihalakakou, G. 2008. On the green roof system: Selection, state of the art and energy potential investigation of a system installed in an office building in Athens, Greece. Renew Energy, 33: 173–177.

Takakura, T., Kitade, S. and Goto, E. 2000. Cooling effect of greenery cover over a building. Energy and Buildings, 31: 1–6.

Theodosiou, T. 2003. Summer period analysis of the performance of a planted roof as a passive cooling technique. Energy and Buildings, 35 (9): 909–917.

Theodosiou, T. 2009. Green roofs in buildings: Thermal and environmental behavior. Advances in Building Energy Research, 3 (1): 271–288.

Wan, K.K.W., Li, D.H.W., Liu, D. and Lam, J.C. 2011. Future trends of building heating and cooling loads and energy consumption in different climates. Building and Environment 46: 223–34.

Wolf, D. and Lundholm, J.T. 2008. Water uptake in green roof microcosms: Effects of plant species and water availability. Ecological Engineering, 33: 179–86.

Wong, N.H., Tay, S.F., Wong, R., Ong, C.L. and Sia, A. 2003. Life cycle cost analysis of rooftop gardens in Singapore. Building and Environment, 38: 499–509.

Yan, B. 2011. The research of ecological and economic benefits for green roof. Applied Mechanics and Materials, 71: 71–8.

Zinzi, M. 2010. Cool materials and cool roofs: Potentialities in Mediterranean buildings. Advances in Building Energy Research, 4 (1): 201–266.