Effectiveness of Outdoor Windcatcher and Mist Cooling in Mitigating Urban Heat and Improving Pedestrian Thermal Comfort

Abstract

Urban heat and the resulting pedestrian thermal discomfort are critical issues in arid cities. This study examines the effectiveness of combining outdoor windcatchers with mist cooling to mitigate urban heat and improve outdoor thermal comfort (OTC). To simulate the effect of the windcatcher and mist cooling on urban canyon, the ENVI-met urban microclimate model was utilized and validated using published experimental and modeling datasets. The validated model was applied to a realistic urban morphology for a case study in Souq Waqif, Doha, Qatar, on a hot summer day (𝑇𝑚𝑎𝑥 = 37.7 °C). Three intervention scenarios—windcatcher alone, mist cooling alone, and an integrated windcatcher–mist cooling system—were assessed against a baseline scenario without interventions. Results showed that the windcatcher alone improved pedestrian-level airflow velocity, increasing it by 5 times compared to the baseline at 0.1 m/s, but decreased temperature by 0.63 °C. The mist cooling alone reduced pedestrian-level temperature by 1.9 °C with negligible airflow change. The integrated windcatcher–mist cooling system lowered air temperature by 3.06 °C and enhanced air velocities by 0.43 m/s at a mist-water flow rate of 45 g/s using three nozzles. Upon using 12 nozzles, the local cooling was amplified, reducing air temperature to 6.4°C. This resulted in a substantial reduction in the Physiological Equivalent Temperature of up to 8.3 °C, hence shifting the thermal sensation by 1 to 2 categories and improving OTC over extended hours of the day. Hence, the windcatcher mist cooling strategy presented an effective sustainable solution for enhanced OTC.