Comparison of Thermal Performance of Broadleaf and Coniferous Trees in Urban Canyons (Case Study: City of Isfahan)

Document Type : Original Article

Author

MSc Faculty Member, Department of Architectural and Building, Technical and Vocational University (TVU), Tehran, Iran.

10.48301/kssa.2022.298183.1650

Abstract

With the growth of urbanization and the increase in the density of buildings, emerging urban valleys face greater problems in terms of pollution and temperature. Severe thermal stresses in these valleys have reduced the level of thermal satisfaction of passers-by. Planting vegetation is one important method of reducing air temperature and improving thermal comfort, particularly on sidewalks. Shading or evaporative cooling helps to improve ambient temperature conditions. Studies conducted in Isfahan show that trees are the most repetitive type of vegetation in the valleys of Isfahan. They create different thermal conditions in the passage. The purpose of this study was to investigate the difference in thermal impact between the most common type of broadleaf tree and the most frequent type of coniferous tree in the urban valleys of Isfahan with different H / W ratio and orientation. Envi-met v4.1 software was used to evaluate the impact of trees with different characteristics in urban valleys. First, through field study, the conditions of urban valleys and recurrent vegetation in the environment were determined. Then, by simulation with the mentioned software, the thermal conditions created in summer and winter in urban valleys were studied and compared. The results show that broadleaf (deciduous) trees performed better under all four directions in summer and reduced pmv by a maximum of 2.5 units. In winter, coniferous (evergreen) trees protect the passages from the wind. The winter cold provided better comfort conditions based on the pmv index. Conditions were improved by a maximum of 0.3 units. However, in general, summer and winter deciduous trees provided the best conditions for thermal comfort. It is recommended that in the city of Isfahan, particularly in densely populated areas such as deep and narrow urban valleys, and on windy roads in winter (with east-west and northeast-south direction) conifers and leaf trees be planted. At the start of passages, conifers should be planted to control the speed and intensity of winter winds.

Keywords

Main Subjects


[1] Jamei, E., Rajagopalan, P., Seyedmahmoudian, M., & Jamei, Y. (2016). Review on the impact of urban geometry and pedestrian level greening on outdoor thermal comfort. Renewable and Sustainable Energy Reviews, 54, 1002-1017. https://doi.org/10.101 6/j.rser.2015.10.104
[2] Fahmy, M., Sharples, S., & Yahiya, M. (2010). LAI based trees selection for mid latitude urban developments: A microclimatic study in Cairo, Egypt. Building and Environment, 45(2), 345-357. https://doi.org/10.1016/j.buildenv.2009.06.014
[3] Shahidan, M. F., Shariff, M. K. M., Jones, P., Salleh, E., & Abdullah, A. M. (2010). A comparison of Mesua ferrea L. and Hura crepitans L. for shade creation and radiation modification in improving thermal comfort. Landscape and Urban Planning, 97(3), 168-181. https://doi.org/10.1016/j.landurbplan.2010.05.008
[4] Givoni, B. (1991). Impact of planted areas on urban environmental quality: A review. Atmospheric Environment. Part B. Urban Atmosphere, 25(3), 289-299. https://doi.o rg/10.1016/0957-1272(91)90001-U
[5] Vailshery, L. S., Jaganmohan, M., & Nagendra, H. (2013). Effect of street trees on microclimate and air pollution in a tropical city. Urban Forestry & Urban Greening, 12(3), 408-415. https://doi.org/10.1016/j.ufug.2013.03.002
[6] Grimmond, C. S. B., & Oke, T. R. (1991). An evapotranspiration-interception model for urban areas. Water Resources Research, 27(7), 1739-1755. https://doi.org/10.1029/91WR00557
[7] Srivanit, M., & Hokao, K. (2013). Evaluating the cooling effects of greening for improving the outdoor thermal environment at an institutional campus in the summer. Building and Environment, 66, 158-172. https://doi.org/10.1016/j.buildenv.2013.04.012
[8] Srivanit, M., & Jareemit, D. (2020). Modeling the influences of layouts of residential townhouses and tree-planting patterns on outdoor thermal comfort in Bangkok suburb. Journal of Building Engineering, 30, 101262. https://doi.org/10.1016/j.jobe.2020.101262
[9] De, B., & Mukherjee, M. (2018). “Optimisation of canyon orientation and aspect ratio in warm-humid climate: Case of Rajarhat Newtown, India”. Urban Climate, 24, 887-920. https://doi.org/10.1016/j.uclim.2017.11.003
[10] Deng, J-Y., & Wong, N. H. (2020). Impact of urban canyon geometries on outdoor thermal comfort in central business districts. Sustainable Cities and Society, 53(2), 101966. https ://doi.org/10.1016/j.scs.2019.101966
[11] Mi, J., Hong, B., Zhang, T., Huang, B., & Niu, J. (2020). Outdoor thermal benchmarks and their application to climate‒responsive designs of residential open spaces in a cold region of China. Building and Environment, 169(3), 106592. https://doi.org/10.1016/j.b uildenv.2019.106592
[12] Ouali, K., El Harrouni, K., Abidi, M. L., & Diab, Y. (2020). Analysis of Open Urban Design as a tool for pedestrian thermal comfort enhancement in Moroccan climate. Journal of Building Engineering, 28(122), 101042. https://doi.org/10.1016/j.jobe.2 019.101042
[13] Sudprasert, S. (2019). Evaluation of energy savings by retrofitting of the building envelope of air-conditioned row house. Journal of Architectural/Planning Research and Studies, 16(1), 83-92. https://so02.tci-thaijo.org/index.php/jars/article/view/152099/138262
[14] Abdallah, A. S. H., & Mahmoud, R. M. A. (2022). Urban morphology as an adaptation strategy to improve outdoor thermal comfort in urban residential community of new assiut city, Egypt. Sustainable Cities and Society, 78, 103648. https://doi.org/10.101 6/j.scs.2021.103648
[15] Akbari, H., Kurn, D. M., Bretz, S. E., & Hanford, J. W. (1997). Peak power and cooling energy savings of shade trees. Energy and Buildings, 25(2), 139-148. https://doi.org/ 10.1016/S0378-7788(96)01003-1
[16] Santamouris, M. (2013). Energy and Climate in the Urban Built Environment. Routledge. https://books.google.com/books/about/Energy_and_Climate_in_the_Urban_Built_En.html?id=_r_9lPbjxX8C
[17] Tan, Z., Chung, S. C., Roberts, A. C., & Lau, K. K-L. (2019). Design for climate resilience: influence of environmental conditions on thermal sensation in subtropical high-density cities. Architectural Science Review, 62(1), 3-13. https://doi.org/10.1080/00038628.201 8.1495612
[18] Mahmoud, H., Ghanem, H., & Sodoudi, S. (2021). Urban geometry as an adaptation strategy to improve the outdoor thermal performance in hot arid regions: Aswan University as a case study. Sustainable Cities and Society, 71, 102965. https://doi.org/10.1016/j.scs.202 1.102965
[19] Abreu-Harbich, L., Labaki, L., & Matzarakis, A. (2012, August 6-10). Thermal bioclimate on idealized urban street canyons in Campinas, Brazil. 8th International Conference on Urban Climates, University College Dublin, Dublin Ireland. https://www.researchgate.n et/publication/262560211_Thermal_bioclimate_on_idealized_urban_street_canyons_in_Campinas_Brazil
[20] Darvish, A., Eghbali, G., & Eghbali, S. R. (2021). Tree-configuration and species effects on the indoor and outdoor thermal condition and energy performance of courtyard buildings. Urban Climate, 37(3), 100861. https://doi.org/10.1016/j.uclim.2021.100861
[21] Kotzen, B. (2003). An investigation of shade under six different tree species of the Negev desert towards their potential use for enhancing micro-climatic conditions in landscape architectural development. Journal of Arid Environments, 55(2), 231-274. https://do i.org/10.1016/S0140-1963(03)00030-2
[22] Leuzinger, S., Vogt, R., & Körner, C. (2010). Tree surface temperature in an urban environment. Agricultural and Forest Meteorology, 150(1), 56-62. https://doi.org/10.1016/j.agrfo rmet.2009.08.006
[23] Correa, E., Ruiz, M. A., Canton, A., & Lesino, G. (2012). Thermal comfort in forested urban canyons of low building density. An assessment for the city of Mendoza, Argentina. Building and Environment, 58, 219-230. https://doi.org/10.1016/j.buildenv.2012.06.007
[24] Gulyás, Á., Unger, J., & Matzarakis, A. (2006). Assessment of the microclimatic and human comfort conditions in a complex urban environment: Modelling and measurements. Building and Environment, 41(12), 1713-1722. https://doi.org/10.1016/j.buildenv.2005. 07.001
[25] Johansson, E., & Emmanuel, R. (2006). The influence of urban design on outdoor thermal comfort in the hot, humid city of Colombo, Sri Lanka. International Journal of Biometeorology, 51(2), 119-133. https://doi.org/10.1007/s00484-006-0047-6
[26] Ng, E., Chen, L., Wang, Y., & Yuan, C. (2012). A study on the cooling effects of greening in a high-density city: An experience from Hong Kong. Building and Environment, 47(1), 256-271. https://doi.org/10.1016/j.buildenv.2011.07.014
[27] Huttner, S., & Bruse, M. (2009, June 29-July 3). Numerical modeling of the urban climate–a preview on ENVI-met 4.0. 7th international conference on urban climate, Yokohama, Japan. https://www.researchgate.net/publication/237757978_Numerical_modeling_of_ the_urban_climate_-_a_preview_on_ENVI-met_40
[28] System, E. A. (2018). Welcome at The EAS Group. EAS. https://www.envimet.com/en/
Volume 19, Issue 4 - Serial Number 60
Art and Architecture | Agriculture
March 2023
Pages 373-404
  • Receive Date: 16 October 2021
  • Revise Date: 04 May 2022
  • Accept Date: 28 May 2022