Evaluating the Impact of the Spatial Scale of Central Courtyards on Outdoor Thermal Comfort in High-Density Residential Complexes (Case Study: The Hot and Dry Climate of Shiraz City)

Raoufat, Ali Akbar; Heidari, Ali Akbar; Paknezhadi, Abdol Hosein; Eskandari, Hamid

doi:10.22034/ijumes.2026.2097300.1391

Evaluating the Impact of the Spatial Scale of Central Courtyards on Outdoor Thermal Comfort in High-Density Residential Complexes (Case Study: The Hot and Dry Climate of Shiraz City)

Articles in Press

Document Type : Case Study

Authors

Ali Akbar Raoufat ¹

Ali Akbar Heidari ²

Abdol Hosein Paknezhadi ¹

Hamid Eskandari ²

¹ Department of Urban Planning and Architecture, Yas.C., Islamic Azad University, Yasuj, Iran

² Department of Technical and engineering, Yasouj university, Yasouj, Iran

10.22034/ijumes.2026.2097300.1391

Abstract

Optimizing the microclimatic behavior of outdoor spaces in high-density residential fabrics is one of the most effective strategies for mitigating human thermal stress and enhancing urban sustainability in hot and dry climates. Aiming to analyze the impacts of geometry, scale, and spatial organization on outdoor thermal comfort, this study evaluates 18 layout scenarios generated by combining four central courtyard typologieswithin a high-density residential complex in Shiraz. The evaluations were conducted under the most critical summer conditions using numerical microclimate simulations. The analytical findings reveal that transitioning from the large-scale, single-courtyard reference model to fragmented and decentralized spatial configurations consistently leads to a reduction in air temperature and mean radiant temperature (Tmrt), thereby improving the Physiological Equivalent Temperature (PET) index across all scenarios. Analyzing the thermodynamic mechanisms governing the spaces indicates that the radiative load (Tmrt) is the primary driver of thermal perception in this climate. The fine-grained square and medium-sized rectangular typologies exhibit the most successful performance in mitigating solar radiative energy and lowering the PET index, primarily due to the reduction of the Sky View Factor (SVF) and the creation of self-shading by the physical built form. Conversely, spacious courtyards transform into thermal traps owing to their low degree of enclosure. Regarding wind flow and relative humidity components, although elongated geometries offer better aerodynamic potential for airflow passage, the minor reduction in wind velocity in fine-grained fabrics due to physical roughness is entirely negligible when compared to the positive effects of shading on mitigating the radiative load. Ultimately, this research emphasizes that the smart combination of compact and linear fine-grained layouts represents the most effective design strategy for achieving sustainable outdoor thermal comfort in residential complexes within hot and dry regions.

Graphical Abstract

Evaluating the Impact of the Spatial Scale of Central Courtyards on Outdoor Thermal Comfort in High-Density Residential Complexes (Case Study: The Hot and Dry Climate of Shiraz City)

Highlights

· Fragmented layouts significantly enhance outdoor thermal comfort in Shiraz.

· Fine-grained square typologies minimize PET index through effective self-shading.

· Radiative load (T_mrt) is identified as the primary driver of hot-dry thermal stress.

· Spacious courtyards act as thermal traps due to high Sky View Factor (SVF).

· Shading benefits in compact fabrics outweigh minor wind velocity reductions.

Keywords

Central courtyard

ENVI-met

hot and dry climate

outdoor thermal comfort

physical scale

Physiological Equivalent Temperature (PET)

· Ahmad, M.W., Mourshed, M., Mundow, D., Sisinni, M. and Rezgui, Y. (2016). Building energy metering and environmental monitoring – A state-of-the-art review and directions for future research. Energy and Buildings/ ELSEVIER /ScienceDirect. http://dx.doi.org/10.1016/j.enbuild.2016.03.059

· Atmaca Ibrahim, Kaynakli Omer, Yigit Abdulvahap. (2007) Effects of radiant temperature on thermal comfort, Building and Environment, Volume 42, Issue 9, Pages 3210-3220, ISSN 0360-1323. https://doi.org/10.1016/j.buildenv.2006.08.009.

· Ballinas, Monica & Morales-Santiago, Sara & Barradas, Victor & Lira, Adriana & Oliva-Salinas, Gerardo. (2022). Is PET an Adequate Index to Determine Human Thermal Comfort in Mexico City? Sustainability. 14. 1-12. DOI: 10.3390/su141912539

· Blocken, Bert., (2014). 50 years of Computational Wind Engineering: Past, present and future. Journal of Wind Engineering and Industrial Aerodynamics, Volume 129, Pages 69-102, ISSN 0167-6105. https://doi.org/10.1016/j.jweia.2014.03.008.

· Emmanuel, R., Rosenlund, H., & Johansson, E. (2007). Urban shading—A design option for the tropics? A study in Colombo, Sri Lanka. Energy and Buildings, 39(7), 813–821.

· https://doi.org/10.1016/j.enbuild.2007.01.007

· Fanger, P. O. (1970). Thermal Comfort: Analysis and Applications in Environmental Engineering. Copenhagen: Danish Technical Press. CABI Record Number: 19722700268

· Höppe, P. (1999). The physiological equivalent temperature—A universal index for the biometeorological assessment of the thermal environment. International Journal of Biometeorology, 43(2), 71–75. https://doi.org/10.1007/s004840050118

· Johansson, E., Thorsson, S., Emmanuel, R., & Krüger, E. (2014). Instruments and methods in outdoor thermal comfort studies – The need for standardization. Urban Climate, 10, 346-366. https://doi.org/10.1016/j.uclim.2013.12.002

· Li, Y., Fei, W., Yang, M., Wang, Y., Du, Y., & Wang, Y. (2025). How to realize large-scale outdoor thermal comfort studies? A systematic review based on OTC characterization, methods and research trends. Frontiers in Sustainable Cities. https://doi.org/10.3389/frsc.2025.1552994

· Lin, T. P., Matzarakis, A., & Hwang, R. L. (2010). Shading effect on long-term outdoor thermal comfort. Building and Environment, 45(1), 213–221. https://doi.org/10.1016/j.buildenv.2009.06.002

· Matzarakis, A., Mayer, H., & Iziomon, M. G. (1999). Applications of a universal thermal index: Physiological equivalent temperature. International Journal of Biometeorology, 43(2), 76–84. https://doi.org/10.1007/s004840050119

· Monteith, J. L., & Unsworth, M. (2013). Principles of environmental physics: Plants, animals, and the atmosphere (4th ed.). Academic Press. 10.1016/B978-0-12-386910-4.00013-5

· Musa, Hala & Asadi, Fawzia & Majeed, Anas. (2024). The Impact of Wind Movement on Providing Thermal Comfort in Urban Design. Technium: Romanian Journal of Applied Sciences and Technology. 24. 39-57. DOI: 10.47577/technium. v24i.11740.

· Oke, T. R., Mills, G., Christen, A., & Voogt, J. A. (2017). Urban Climates. Cambridge University Press. ISBN 9781139016476. https://doi.org/10.1017/9781139016476

· Sadeghi, A. R., & Bahadori, Y. (2021). Urban sustainability and climate issues: The effect of physical parameters of streetscape on the thermal comfort in urban public spaces (Case study: Karimkhan-e-Zand Street, Shiraz, Iran). Sustainability, 13(19), 10886. https://doi.org/10.3390/su131910886

· Santos Nouri, A., Charalampopoulos, I., Matzarakis, A. (2022). The application of the physiologically equivalent temperature to determine impacts of locally defined extreme heat events within vulnerable dwellings during the 2020 summer in Ankara, Sustainable Cities and Society, Volume 81, 103833, ISSN 2210-6707. https://doi.org/10.1016/j.scs.2022.103833

· Sargazi, M.A., Heidari, A., Davtalab, J. et al. (2026). Comparative reliability assessment of PET and UTCI thermal comfort indices using Monte Carlo simulation in urban microclimates. Scientific Reports 16, 3431. https://doi.org/10.1038/s41598-025-33440-6

· Spiridonov, Vlado and Curic, Mladjen. (2021). Chapter 7 - Air Temperature, Fundamentals of Meteorology, Springer Cham, Pages 73-86 / ResearchGate. https://researchgate.net/publication/348123826_Fundamentals_of_Meteorology

· Taleghani, M., Kleerekoper, L., Tenpierik, M., & van den Dobbelsteen, A. (2015). Outdoor thermal comfort within five different urban forms in the Netherlands. Building and Environment, 83, 65–78. https://doi.org/10.1016/j.buildenv.2014.03.01

· Thorsson, S., Lindberg, F., Eliasson, I., & Holmer, B. (2007). Different methods for estimating the mean radiant temperature in an outdoor urban setting. International Journal of Climatology, 27(14), 1983–1993. https://doi.org/10.1002/joc.1537

· Zhu, J., Feng, J., Lu, J., Chen, Y., Li, W., Lian, P. and Zhao, X. (2023). A review of the influence of courtyard geometry and orientation on microclimate. Building and Environment 236 (2023) 110269. ELSEVIER/ ScienceDirect. https://doi.org/10.1016/j.buildenv.2023.110269