Parametric Optimization of Jaali Void Ratios for Urban Heat Island Mitigation in Bhopal’s Composite Climate

Abstract - The rapidly aggravating Urban Heat Island (UHI) intensity, characterized by nocturnal temperature rises of 3-4°C relative to the outer areas, requires climate-resilient passive envelope design in Bhopal. The city’s location in a composite climatic zone is characterized by high summer temperatures of 42-45°C and high monsoon season humidity, making façade performance a complex task. The rising trend of high SHGC glazed façades in the commercial sector has further increased cooling loads by 30-40% in urban areas. This research aims to explore the optimization of Jaali void ratios between 25-65% as a passive façade design to counter UHI in Bhopal. The meta-synthesis of 25 validated datasets from heritage building audits and post-occupancy studies constitutes the research methodology. Comparative analysis includes Hawa Mahal, Mehrangarh Fort, Aranya Housing, and the New Parliament House. Results show that void ratios between 38-52% offer the best multi-objective performance, reducing predicted canyon temperatures by 2.5-3.2°C, ventilation rates by 1.8-2.3 ACH, and daylight factors by 3.2-4.1%. A calibrated value of 42% is found optimal for south-west facing façades in Bhopal’s composite climate. Keywords: Urban Heat Island (UHI), climate-resilient architecture, passive façade design, Jaali void ratio optimization, composite climate, Bhopal, solar heat gain coefficient (SHGC),