Bio-jaali: Reimagining vernacular passive cooling screens with mycelium-based composites

Climate change and severe urban heat stress in South Asian megacities are driving an amplified reliance on energy-intensive air conditioning, necessitating urgent low-carbon cooling solutions. This study addresses this challenge by reinterpreting the traditional jaali, a perforated passive-cooling screen, using mycelium-based composites (MBCs) to create a novel, climate-responsive, low-carbon façade system: bio-jaali. We assessed the performance of the bio-jaali through a holistic approach, combining historical climate data analysis (New Delhi, 1991–2019), dynamic building energy simulations, and laboratory bio-fabrication and hygrothermal testing. This integrated methodology is a key achievement, bridging materials science with dynamic simulation to improve building-scale performance. The climate analysis revealed a 60% increase in ‘danger-level’ heat-stress hours over the 28 years. Dynamic simulation results showed that replacing the conventional sandstone jaali with the bio-jaali yielded substantial thermal benefits: a 3.5°C (10%) reduction in the annual average indoor operative temperature and a drop in peak summer indoor temperatures by up to 14.8°C. Consequently, the annual cooling energy demand was lowered by 50.4%. Furthermore, laboratory cyclic humidity tests demonstrated the MBCs’ potential for evaporative cooling, confirming they remained dimensionally stable (<3% change) while absorbing up to 17.2% moisture. The bio-jaali is highlighted as a culturally rooted, bio-based solution that significantly reduces reliance on active cooling. This research contributes new knowledge on the building-scale performance, climate adaptability, and cyclic hygrothermal stability of MBC facades. We position the bio-jaali as a robust prototype for integrating passive and adaptive thermal regulation, advancing circular construction practices for sustainable architecture in heat-stressed urban environments.