Due to the increasing demand for air conditioners to maintain thermal comfort in buildings, it is necessary to search for alternatives that can reduce the soaring temperature and meet total air conditioning demands. There are several proven technologies for maintaining thermal comfort in buildings of which the use of phase change material (PCM) in buildings provides improved thermal comfort with fewer energy requirements. The present study analyzes the impact of the incorporation of PCM in roofs on the thermal behavior of buildings. The experiments were conducted in two identical model building roofs with and without the implementation of PCM. A numerical model was developed to find the effect of variation in the PCM layer thickness and month wise temperature variations. To get minimum variation in the results, the simulation was run continuously for 5 days assuming average climatic conditions. The results showed that temperature fluctuations in the room were reduced with the use of PCM, and also the average peak temperature rise was reduced by 2–4°C. The increased PCM layer thickness resulted in decreased energy demand for maintaining the required thermal comfort in buildings at an almost constant temperature.