Amit Kumar, Dipankar Bhanja, Agnimitra Biswas
The increasing cooling energy demand of modern buildings poses significant challenges to energy security and environmental sustainability, particularly in warm and humid regions such as Northeast India. In this study, a representative residential building model suitable for Northeast Indian climatic conditions was analyzed to evaluate cooling load, indoor temperature variation, relative humidity, thermal comfort index, and associated carbon emissions. Simulations were performed using the EnergyPlus engine within the DesignBuilder software. Four phase change materials (PCMs) – n-octadecane, RT-26, capric acid, and calcium chloride hexahydrate (CaCl2·6H2O) were individually incorporated into the building envelope to assess their thermal performance. Among the materials investigated, n-octadecane exhibited the most effective cooling performance under warm and humid conditions. Parametric analyses were further conducted to examine the influence of PCM placement in three external walls, indoor temperature setpoints, natural ventilation, and occupancy patterns. The results demonstrate that PCM integration can reduce cooling load by approximately 15–20%, along with an average indoor temperature reduction of about 2°C. Natural ventilation significantly enhanced PCM effectiveness when outdoor air temperatures were below the indoor setpoint. Additionally, the use of PCMs improved indoor thermal comfort by 12.91% to 31%. A carbon emission reduction of 16.98% was achieved for PCM integration in three external walls at a set temperature of 24°C under natural ventilation conditions. These findings highlight the potential of PCMs as an effective passive cooling solution for energy-efficient and sustainable building design in Northeast India.