Facilitating indoors with healthy and fresh air along with adequate thermal comfort using less energy is a true challenge in buildings located in hot climates. The present work aims to improve the thermal comfort of office occupants by incorporating phase change material (PCM)/insulation integration coupled with natural ventilation. Four building models integrated with various combinations of PCM and insulation were analyzed using DesignBuilder software with respect to Chennai climatic conditions. It was understood from the analysis that the PCM integration in the building roof and walls of Case 3 did not provide adequate thermal comfort for the considered climate. But the presence of insulation in Cases 2 and 4 maintained an average hourly operative temperature of 26.8 °C and 26.6 °C, including extreme summer. These temperatures are well within the tolerable temperature range of humans. Also, it is observed that Case 4 comparatively reduced the thermal comfort index by a maximum of 0.25 (reduction in warm sensation). Further optimization of Case 4 yielded an insulation and PCM thickness of 50 mm and 30 mm, respectively. The recommended building model was evaluated with a thermal comfort index not exceeding 1.7 until the end of office hours, throughout the year for Chennai climate.