Morphological Trade-offs in Urban Microclimates: A Challenge for Achieving Sustainable Environmental Comfort

Document Type : Research Paper

Authors

Department of Architecture, Faculty of Art and Architecture, Bu-Ali Sina University, Hamedan, Iran.

10.22059/jes.2026.408070.1008662

Abstract

Objective: The inherent complexity of urban microclimates drives proposed strategies for enhancing habitability and comfort into pathways that often yield multiple, sometimes conflicting effects; thus, optimizing one comfort metric can inadvertently degrade others. This is crucial, as the improper placement of any urban element can cause mitigation strategies to produce effects contrary to their intended purpose. A sustainable and resilient urban environment can be achieved when optimal parameters are quantified and applied with consideration for all dimensions of comfort and livability.
Method: To address the identified gap, this research utilized ANSYS CFX CFD software to calculate and benchmark the performance efficiencies of common urban morphological components against various microclimate comfort metrics. Subsequently, a multi-criteria decision-making framework was applied to logically integrate these quantitative performance metrics, thereby identifying the optimal morphological configuration that satisfies the required balance of all comfort factors. This research established a foundational selection basis by first categorizing urban building block elements based on shared structural characteristics. The categories were then systematically compared based on their influence on street canyon temperature, pressure, and wind velocity. Finally, a comprehensive ranking system was derived to guide the selection of the optimal form and strategy aligned with specific urban texture conditions. The prevalence of a common structural typology across all examined groups helped the accurate quantification of the percentage of usefulness gained from modifying specific building geometries. Given the critical air quality of Tehran, all simulation input values were proportionally calibrated to the city’s climate profile, ensuring the derived solutions were directly relevant to improving its environmental health.
Results: Across all tested variables, changes to the fundamental building block form and geometry proved to be the dominant factor in improving holistic street canyon environments, resulting in performance efficiencies reaching 70% compared to standard designs. Conversely, strategies focused on localized volumetric changes or facade-based flow modification achieved significantly lower effectiveness, improving street-canyon comfort metrics by 40%.
Conclusions: This study subsequently introduced a ranking mechanism to systematically evaluate and prioritize intervention tools according to their measurable impact on street-canyon microclimate performance. Focusing the analysis on the primary drivers—temperature, wind speed, and pressure—allows researchers to clearly demonstrate how macro-scale structural modifications exert a greater control over these fundamental factors, thereby minimizing inherent inter-variable conflicts.

Keywords

Main Subjects

References

رازجویان، محمود (1386). آسایش در پناه باد. دانشگاه شهید بهشتی. تهران.
شرکت کنترل کیفیت هوای تهران (1403). شاخص کیفیت هوای تهران، شرکت کنترل کیفیت هوای تهران. https://airnow.tehran.ir
شهرداری تهران (1392). ضوابط و مقررات طرح تفصیلی جدید تهران، معاونت شهرسازی و معماری شهرداری تهران.  https://shora.tehran.ir
  Allegrini, J. & Carmeliet, J. (2017). Coupled CFD and building energy simulations for studying the impacts of building height topology and buoyancy on local urban microclimates. Urban Climate, 21, 278-305. https://doi.org/10.1016/ j.uclim.2017.07.005
ANSYS Inc. (2017a). ANSYS CFX Reference Guide (Release 18.0). ANSYS Inc. https://ansys.com
ANSYS Inc. (2017b). ANSYS CFX-Solver Theory Guide (Release 18.0). ANSYS Inc. https://ansys.com
Bas, H., Andrianne, T., Reiter, S.  (2024). City configurations to optimise pedestrian level ventilation and wind comfort. Sustainable Cities and Society, 114, 105745. https://doi.org/10.1016/j.scs.2024.105745
Chew, L.W. & Norford, L.K. (2018). Pedestrian-level wind speed enhancement in urban street canyons with void decks. Building and Environment, 146, 64-76. https://doi.org/10.1016/j.buildenv.2018.09.039
Cui, D., Liang, G., Hang, J., Yang, Z., Huang, Z., Mak, C.M.  (2024). Effects of envelope features on building surface temperature and ventilation performance in 2D street canyons. Urban Climate, 56, 102011. https://doi.org/10.1016/j.uclim.2024.102011
Ding, S., Huang, Y., Cui, P., Wu, J., Li, M., Liu, D.  (2019). Impact of viaduct on flow reversion and pollutant dispersion in 2D urban street canyon with different roof shapes - Numerical simulation and wind tunnel experiment. Science of The Total Environment, 671, 976-991. https://doi.org/10.1016/j.scitotenv.2019.03.391
Fluid Codes. (2025). ANSYS Engineering Simulation Solutions. Fluid Codes. https://fluidcodes.com
Foken, T. (2021). Springer Handbook of Atmospheric Measurements. First ed., Springer Cham. https://doi.org/10.1007/ 978-3-030-52171-4
 Guo, C., Buccolieri, R., Gao, Z. (2019). Characterizing the morphology of real street models and modeling its effect on thermal environment. Energy and Buildings, 203, 109433. https://doi.org/10.1016/j.enbuild.2019.109433
Hoffmann, K.A. & Chiang, S.T. (2000). Computational Fluid Dynamics. Fourth Edition, Volume III, Engineering Education System, Wichita, Kansas, 67208-1078, USA.
Incropera, F.P., Dewitt, D.P., Bergman, T.L., Lavine, A.S. (2011). Fundamentals of Heat and Mass Transfer. Seventh Edition, John Wiley & Sons, USA.
Kamiński, M., Cieślik-Guerra, U.I., Kotas, R., Mazur, P., Marańda, W., Piotrowicz, M., Sakowicz, B., Napieralski, A., Trzos, E., Uznańska-Loch, B., Rechciński, T., Kurpesa, M. (2016). Evaluation of the impact of atmospheric pressure in different seasons on blood pressure in patients with arterial hypertension. International Journal of Occupational Medicine and Environmental Health, 29(5), 783-792.  https://doi.org/10.13075/ijomeh.1896.00546
Karimimoshaver, M., Khalvandi, R., Khalvandi, M. (2021). The effect of urban morphology on heat accumulation in urban street canyons and mitigation approach. Sustainable Cities and Society, 73, 103127. https://doi.org/10.1016/ j.scs.2021.103127
Karimimoshaver, M., Khalvandi, R., Özkazanç, B. (2025). Evaluation of mutual effects of design needs of urban blocks on improving energy efficiency and providing thermal comfort in open spaces, Case study: Hamedan City. Iranica Journal of Energy & Environment, 16(2), 439-452. https://doi.org/10.5829/ijee.2025.16.02.14
Karimimoshaver, M. & Khalvandi, R. (2026). The influence of building height on microclimate and human activities in urban open spaces. City and Environment Interactions, 29, 100283. https://doi.org/10.1016/j.cacint. 2025.100283
Karimimoshaver, M. & Shahrak, M.S. (2022). The effect of height and orientation of buildings on thermal comfort. Sustainable Cities and Society, 79, 103720. https://doi.org/10.1016/j.scs.2022.103720
Khalvandi, R. & Karimimoshaver, M. (2023). The optimal ratio in the street canyons: Comparison of two methods of satellite images and simulation. Building and Environment, 229, 109927. https://doi.org/10.1016/j.buildenv. 2022.109927
Khalvandi, R. & Karimimoshaver, M. (2025a). Urban street canyons and heat islands: A systematic review on morphological solutions. Results in Engineering, 27, 106542. https://doi.org/10.1016/j.rineng. 2025.106542
Khalvandi, R. & Karimimoshaver, M. (2025b). Optimizing urban block forms to improve street canyon microclimates and pedestrian comfort. Energy and Built Environment,  https://doi.org/10.1016/ j.enbenv.2025.08.001
Mirabi, E. & Davies, P.J. (2022). A systematic review investigating linear infrastructure effects on Urban Heat Island (UHIULI) and its interaction with UHI typologies. Urban Climate, 45, 101261. https://doi.org/10.1016/j.uclim. 2022.101261
Mohammad, P., Aghlmand, S., Fadaei, A., Gachkar, S., Gachkar, D., Karimi, A. (2021). Evaluating the role of the albedo of material and vegetation scenarios along the urban street canyon for improving pedestrian thermal comfort outdoors. Urban Climate, 40, 100993. https://doi.org/10.1016/ j.uclim.2021.100993
Mun, D., Kang, G., Yang, M.,  Kim, J. (2024). How trees’ drag and cooling effects influence airflow and temperature distributions around a street canyon. Building and Environment, 264, 111913. https://doi.org/10.1016/j.buildenv. 2024.111913
Muniz-Gäal, L.P., Pezzuto, C.C., de Carvalho, M.F.H., Mota, L.T.M.  (2020). Urban geometry and the microclimate of street canyons in tropical climate. Building and Environment, 169, 106547. https://doi.org/10.1016/j.buildenv.2019.106547
Nosek, Š., Fuka, V., Radović, J., Babuková, Z., Jaňour, Z. (2025). Can deeper street canyons ventilate better? An analysis of roof geometries and aspect ratios with a focus on pollutant dynamics. Building and Environment, 270, 112528. https://doi.org/10.1016/j.buildenv. 2025.112528
Razjouyan, M. (2007). Wind and Comfort, Design with Climate. Tehran, Iran, Shahid Beheshti University publishing, P. 15. [In Persian]
Reiminger, N., Vazquez, J., Blond, N., Dufresne, M., Wertel, J.  (2020). CFD evaluation of mean pollutant concentration variations in step-down street canyons. Journal of Wind Engineering and Industrial Aerodynamics, 196, 104032. https://doi.org/10.1016/j.jweia. 2019.104032
Song Jon, K., Luo, Y., Hyok Sin, C., Cui, P., Huang, Y., Tokgo, J. (2023). Impacts of wind direction on the ventilation and pollutant dispersion of 3D street canyon with balconies. Building and Environment, 230, 110034. https://doi.org/10.1016/j.buildenv. 2023.110034
Tang, H., Chen, W., Li, C.  (2024). Experimental and theoretical study on building integrated radiative cooling with a limited sky-view factor. Journal of Building Engineering, 97, 110948. https://doi.org/10.1016/ j.jobe.2024.110948
Tehran Air Quality Control Company (2024). Tehran Air Quality Index. Tehran Air Quality Company https://airnow.tehran.ir [In Persian]
Tehran Municipality (2013). Rules and regulations of the new detailed plan of Tehran, Municipality of Tehran, Deputy of Urban planning and Architecture. https://shora.tehran.ir [In Persian]
Thierry, J., Herpin, S., Levi, R., Canonne, D., Demotes-Mainard, S., Cannavo, P., Lemesle, D., Brialix, L., Rodriguez, F., Bournet, P.E. (2024). Impact of a water restriction on the summer climatic benefits of trees inside an outdoor street canyon scale model. Building and Environment, 261, 111722. https://doi.org/10.1016/j.buildenv. 2024.111722
Wang, H. & Ngan, K. (2025). Turbulent flow over street canyons with balconies. Urban Climate, 59, 102331. https://doi.org/10.1016/j.uclim.2025.102331
Wu, Y. & Chen, H. (2023). Optimizing block morphology for reducing traffic pollutant concentration in adjacent external spaces of street canyons: A machine learning approach. Building and Environment, 242, 110587. https://doi.org/ 10.1016/j.buildenv.2023.110587
Yang, M., Ma, C.P., Zhao, S.X., Zhao, F.Y., Guo, J.H.  (2025). Aiding and opposing cooling the street canyon through trees and water bodies: Conflicting effects from temperature reduction and ambient humidification. Building and Environment, 270, 112513.  https://doi.org/ 10.1016/j.buildenv.2024.112513
Zhang, T., Fu, X., Qi, F., Shen, Y., Xu, P., Tao, Y., Liu, T., Song, Y.  (2025). Optimizing pedestrian thermal comfort in urban street canyons for summer and winter: Tree planting or low-albedo pavements? Sustainable Cities and Society, 120, 106143. https://doi.org/10.1016/ j.scs.2025.106143
Zhao, Q., Tao, L., Song, H., Lin, Y., Ji, Y., Geng, J., Yu, K., Liu, J. (2025). Mitigation pathways of urban heat islands and simulation of their effectiveness from a perspective of connectivity. Sustainable Cities and Society, 124, 106300. https://doi.org/10.1016/ j.scs.2025.106300
Zheng, J., Ou, Z., Xiang, Y., Li, J., Zheng, B.  (2025). How can street interface morphology effect pedestrian thermal comfort: A case study of the old town of Changsha, China. Urban Climate, 60, 102341. https://doi.org/10.1016/ j.uclim.2025.102341
Journal of Environmental Studies
Volume 51, Issue 4
March 2026
Pages 473-492

Files

Share

How to cite

Statistics