CFD-Based Evaluation of Courtyard Proportions on Indoor Air Quality in Hot and Humid Residential Buildings (Case Study: Traditional Houses in Bushehr city, Iran)

Abdoli, Seyed Sajjad; Shahabzadeh, Marjan; Eskandari, Hamid

doi:10.22034/ijumes.2025.2073164.1339

CFD-Based Evaluation of Courtyard Proportions on Indoor Air Quality in Hot and Humid Residential Buildings (Case Study: Traditional Houses in Bushehr city, Iran)

Document Type : Case Study

Authors

Seyed Sajjad Abdoli ¹

Marjan Shahabzadeh ²

Hamid Eskandari ³

¹ Department of Architecture, Shi.C., Islamic Azad University, Shiraz, Iran

² Department of Urban Planning and Architecture, Shi.C., Islamic Azad University, Shiraz, Iran.

³ Department of Architecture, Yas.C., Yasuj University, Yasuj, Iran

10.22034/ijumes.2025.2073164.1339

Abstract

Natural ventilation plays a critical role in improving indoor air quality and reducing energy consumption in residential buildings located in hot and humid climates. Among passive design strategies, the central courtyard has long been recognized as an effective architectural element for enhancing airflow and thermal performance. However, the quantitative influence of courtyard proportions on indoor ventilation efficiency remains insufficiently explored.The data collection method is library-based and field collection using researcher-centered collections. Subsequently, simulation is performed on the model presented in this phase for evaluation based on criteria and indicators obtained from the main variables in the software. After the climatic study of Bushehr city, Design Builder software is used to analyze and simulate the case studies of the research, which includes 6 historical houses: Haj Rais house, Dehdashti house, Golshan House, Tayyeb house, Azin House, and Nozari house in Bushehr city, which were selected based on the 4 criteria of the existence of a central courtyard. The findings of this study show that medium to high aspect ratios, approximately 1 to 2.1, have significant potential to improve ventilation on the first floor compared to the ground floor, provided that the openings are aligned with the prevailing wind of the area and that there are air flow paths through the openings. Ratios lower than 0.7 generally result in less ventilation on the first floor, unless the facade and openings are designed to direct the prevailing wind inward. The results demonstrate that an integrated consideration of courtyard proportions, opening configuration, and wind orientation can substantially improve natural ventilation performance in hot and humid climates. These results provide practical design guidelines for optimizing courtyard-based residential buildings and reducing reliance on mechanical cooling systems.

Graphical Abstract

CFD-Based Evaluation of Courtyard Proportions on Indoor Air Quality in Hot and Humid Residential Buildings (Case Study: Traditional Houses in Bushehr city, Iran)

Highlights

Courtyard aspect ratio is the primary determinant of natural ventilation performance, with medium to high ratios (1.0–2.1) consistently producing stronger airflow channels and higher air velocities in interior spaces compared to lower ratios.

Courtyards with length-to-width ratios below 0.7 significantly underperform, as airflow dissipates within the courtyard space, weakening pressure differentials and reducing ventilation on upper floors unless façade openings are deliberately wind-aligned.

First-floor rooms are more sensitive to courtyard proportions than ground-floor spaces; in optimized configurations, first-floor ventilation performance can actually exceed that of the ground floor despite uniform building height.

Courtyard elongation aligned with the prevailing wind direction amplifies ventilation gains, enabling external airflow to be drawn in and distributed both vertically and horizontally through the building.

Effective natural ventilation cannot be achieved through courtyard geometry alone; it emerges from the integrated interaction of courtyard proportions, building height, façade opening configuration, and prevailing wind orientation.

Keywords

Bushehr City

central courtyard

Design Builder software

Indoor air quality

natural ventilation

residential buildings

Bai, C.; Zhan, J.;Wang, H.; Yang, Z.; Liu, H.; Liu,W.;Wang, C.; Chu, X.; Teng, Y. (2023)Heating choices and residential willingness to pay for clean heating: Evidence from a household survey in rural China. Energy Policy, 178, 113617. https://doi.org/10.1016/j.enpol.2023.113617

Figueroa-Lopez, A.; Arias, A.; Oregi, X.; Rodriguez, I. (2021) Evaluation of passive strategies, natural ventilation and shading systems, to reduce overheating risk in a passive house tower in the north of Spain during the warm season. J. Build. Eng., 43, 102607. https://doi.org/10.1016/j.jobe.2021.102607

Fine, J.P.; Zhang, S.; Li, Y.; Touchie, M.F. (2022) Analysis of solar chimney ventilation systems in high-rise residential buildings using parallel flow networks. Build. Environ., 218, 109096 https://doi.org/10.1016/j.buildenv.2022.109096

Gao, Y.; He, F.; Meng, X.;Wang, Z.; Zhang, M.; Yu, H.; Gao,W. (2020) Thermal behavior analysis of hollow bricks filled with phase-change material (PCM). J. Build. Eng., 31, 101447. https://doi.org/10.1016/j.jobe.2020.101447

Ghobadian, V. (2009). Sustainable Traditional Buildings of Iran, A Climatic Analysis, Islamic Azad University, Universal Publisher, Beirut.

Hou, J.; Zhang, T.; Liu, Z.; Hou, C.; Fukuda, H. (2022) A study on influencing factors of optimum insulation thickness of exterior walls for rural traditional dwellings in northeast of Sichuan hills, China. Case Stud. Constr. Mater., 16, e01033. https://doi.org/10.1016/j.cscm.2022.e01033

Hussein, M.; Maghrabie Abdelkareem, M.A.; Elsaid, K.; Sayed, E.T.; Radwan, A.; Rezk, H.; Wilberforce, T.; Abo-Khalil, A.G.; Olabi, A.G. (2022) A review of solar chimney for natural ventilation of residential and non-residential buildings. Sustain. Energy Technol. Assess., 52 Pt B, 102082.

Karyono, K.; Abdullah, B.M.; Cotgrave, A.J.; Bras, A. (2020) The adaptive thermal comfort review from the 1920s, the present, and the future. Dev. Built Environ., 4, 100032. https://doi.org/10.1016/j.dibe.2020.100032

Lim SS, Vos T, Flaxman AD, et al. (2012) A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet.;380:2224-2260. doi:10.1016/S0140-6736(12)61766-8.

Lin, Y.; Zhao, L.; Yang,W.; Hao, X.; Li, C.-Q. (2021) A review on research and development of passive building in China. J. Build. Eng., 42, 102509. https://doi.org/10.1016/j.jobe.2021.102509

Logue J.M, Price P.N, Sherman M.H, (2012) Singer BC. A method to estimate the chronic health impact of air pollutants in U.S. residences. Environ Health Perspect.;120:216-222.

Park, S.; Lee, S.; Yeo, M. S.; Rim, D. (2023) Performance of a heat recovery ventilation system for controlling human exposure to airborne particles in a residential building. Build. Environ., 239, 110412. https://doi.org/10.1016/j.buildenv.2023.110412

Piselli, C.; Prabhakar, M.; De Gracia, A.; Saffari, M.; Pisello, A.L.; Cabeza, L.F. (2020) Optimal control of natural ventilation as passive cooling strategy for improving the energy performance of building envelope with PCM integration. Renew. Energy., 162, 171–181. https://doi.org/10.1016/j.renene.2020.07.043

Shen, H.-Y.; Zhang, Y.; Lu, X.-Y.; Chen, L.-B.; Zhu, N.-Z.; Xiao, H.; Yang, G.; Huang, C.; Dai, X.; Ye, J.; et al. (2025) How indoor decoration materials contribute to phthalates pollution: Uncovering occurrences, sources, and their implications for environmental burdens in households. J. Hazard. Mater., 490, 137719. https://doi.org/10.1016/j.jhazmat.2025.137719

Wen, Y.; Lau, S.-K.; Leng, J.; Zhou, K.; Cao, S. J. (2023) Passive ventilation for sustainable underground environments from traditional underground buildings and modern multiscale spaces. Tunn. Undergr. Space Technol., 134, 105002. https://doi.org/10.1016/j.tust.2023.105002

Zoure, A.N.; Genovese, P.V. (2023) Implementing natural ventilation and daylighting strategies for thermal comfort and energy efficiency in office buildings in Burkina Faso. Energy Rep., 9, 3319–3342. https://doi.org/10.1016/j.egyr.2023.02.017

Zune, M.; Tubelo, R.; Rodrigues, L.; Gillott, M. (2021) Improving building thermal performance through an integration of Passivhaus envelope and shading in a tropical climate. Energy Build., 253, 111521. https://doi.org/10.1016/j.enbuild.2021.111521