In this study, the experimental investigates the potential of Phase Change Materials (PCMs) in enhancing the thermal efficiency of building envelopes in hot and humid climates. The study involves constructing rooms with and without PCM, both in single and double layers and evaluating their thermal behaviour in the extreme heat of Chennai. The chosen commercial organic PCM, with a melting range of 35°C to 40°C, aligns with the temperature variations at the site. Experimental results reveal that the double-layer PCM building envelope exhibits a maximum temperature variation reduction of 8.5°C compared to a single-layer PCM. Validation through experimental and numerical simulations using ANSYS workbench supports the findings. The study considers various PCM temperature ranges, and under free-floating ambient conditions, the PCM-installed room demonstrates a significant drop in indoor air temperature compared to the room without PCM. The percentage of latent heat energy utilized by the PCM to achieve specific temperature differences is also presented, showcasing the effectiveness of PCM integration in mitigating high energy consumption associated with air conditioning in hot climates. The experimental results were validated using experimental and numerical simulation using the ANSYS workbench. © 2024 Elsevier B.V., All rights reserved.