New Delhi: Air pollution and urban heat cancel out 88% of Delhi’s comfortable hours in a year. According to the latest research, Delhi experiences around 2,210 thermally comfortable hours in a year, defined using an outdoor temperature range of 18 to 31 degrees Celsius. However, 1,951 of these hours coincide with poor air quality (AQI above 150), leaving just 259 hours in a year for residents to enjoy both clean air and comfortable temperatures.Chennai mirrored Delhi’s challenge, with 88% of its comfortable hours too impacted by air pollution, suggesting that the convergence of climate stress and ambient pollution is becoming more common across Indian metros. The study found the situation to be better in other cities like Bengaluru and Ahmedabad, providing more usable outdoor conditions than Delhi.The research by CEPT University and Respirer Living Sciences advocated Personalised Environmental Control Systems (PECS) to design and manage better indoor environment to provide comfort in polluted and warming cities. The study said that conventional building operations, which are either based on fully sealed air-conditioned spaces or unfiltered natural ventilation, no longer met the needs of urban India, especially in cities where thermal comfort and clean air rarely overlapped. The study proposed the incorporation of a personalised environment which offered localised thermal comfort and air quality using proper ventilation.The study also introduced the concept of “temporal mixed-mode buildings” or designs that adapt dynamically to outdoor conditions. These buildings combine sensor-based feedback with intelligent ventilation and filtration strategies, enabling occupants to breathe clean air without unnecessary energy expenditure.“PECS contributes to both short-term and long-term health and energy performance outcomes. With ongoing improvements in AQI across Indian cities, there is growing potential for occupants to utilise natural ventilation when outdoor conditions permit,” said Rajan Rawal of CEPT University. “Nevertheless, PECS continues to offer substantial energy savings under prevailing conditions, serving as a contextually appropriate strategy to ensure thermal comfort, safeguard occupant health, and reduce energy demand. PECS work especially well in conjunction with low-energy solutions like ceiling fans and task-based ventilation, which enhance perceived comfort through increased air movement without the energy costs of cooling the entire space.”The modelling conducted by the research team also showed that buildings using PECS could achieve major energy savings for ventilation, which is 72% in Chennai, 70% in Ahmedabad, and 68% in Delhi, when compared with conventional air-conditioned setups.“PECS is also an equity solution. It allows even schools, community centres or homes without full heating, ventilation, air conditioning (HVAC) systems to deliver healthier environments. We’re not just rethinking comfort; we’re reimagining what low-energy, people-centric buildings can look like in polluted and warming cities,” said Ronak Sutaria, founder and CEO, Respirer Living Sciences.
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