Multi-objective optimization of urban block configuration to enhance outdoor thermal comfort: A case study of district 12, Tehran
Mozhgan Mousaeipour, Haniyeh Sanaieian, Mohsen Faizi, Ainaz Alafchi, S. M. Amin Hosseini
Abstract
Urban block configuration significantly impacts outdoor thermal comfort (OTC). While many studies have examined the effects of individual variables such as building orientation and the height-to-width ratio (H/W) on OTC, there has been limited systematic optimization of multiple configuration variables simultaneously. This study aims to enhance OTC by developing a flexible parametric model capable of simulating a wide range of urban block configurations through variations in key geometric parameters. The model implicitly integrates typical residential block arrangements—such as linear, isolated, and sinusoidal layouts—by adjusting inter-block spacing, canyon width, orientation, and relative row positions. A multi-objective genetic algorithm (NSGA-II) was applied to identify optimal configurations, followed by simulation, optimization, and sensitivity analysis. To further evaluate the impact of different layouts on thermal comfort indices and microclimatic conditions, the best and worst scenarios were compared using ENVI-met software. The simulation tool was validated through field measurements. District 12 of Tehran, currently undergoing redevelopment and facing critical thermal stress, was selected as the case study. Among the 1,000 generated scenarios, six optimal solutions were identified, with Solution 2 determined as the most effective. Compared to the worst-performing configuration, this solution achieved an average reduction—during the time interval from 7:00 AM to 8:00 PM—of 10.26°C in Mean Radiant Temperature (MRT), 3.48°C in Universal Thermal Climate Index (UTCI), 3.77°C in Physiological Equivalent Temperature (PET), and 0.49°C in Air Temperature (TA). These results emphasize that block orientation and spacing exert the greatest influence on OTC, while urban block configuration has minimal effect on relative humidity but a notable impact on wind speed. Overall, this study provides a scalable and practical framework for climate-responsive urban design by identifying configurations that optimize outdoor thermal comfort in hot and semi-arid climates.