Currently, the building industry is focusing on the requirement for high energy utilization. It is critical to optimize energy use by utilizing renewable resources. The use of phase-change materials in thermal energy storage systems is gaining popularity in passive applications for green buildings due to their innovative approach. The proposed work focuses on the incorporation of MWCNT additive sodium poly acrylate as PCM materials into the walls, panels, and roofs of passive structures, as well as the assessment of optimal energy consumption in green buildings via indoor environmental quality (IEQ). A novel framework was developed using the response surface method and the hill climbing technique to identify the most efficient use of energy output, charging time, and heat transfer rate based on the input phase such as input air condition temperature (25–28 °C), air conditioner flow rate (100–600 cfm) and relative humidity (35–55%). According to the results, the optimal energy transfer rate of the PCM wall was found to be 53.86 during a charging duration of 39 min. The amount of thermal energy stored by the PCM wall to maintain the room temperature of 26 degrees Celsius was discovered to be 15,400 kJ. This energy is adequate to keep the room temperature stable for 3 days. © 2024 Elsevier B.V., All rights reserved.