The planning for Saudi Arabia's NEOM city, a smart city featuring tourism attractions, began in 2017 and the first phase will be operational by 2025. The employment of passive-based techniques to minimize energy consumption is one of the requirements of smart cities. In this study, the thermal behavior of three buildings in the presence of PCM is discussed. The first building has no PCM and has a wall thickness of 29 cm, but the second and third buildings have PCM and a wall thickness of 34 cm. In general, the installation of PCM in the northern, southern, eastern, and western walls is beneficial, as it reduced heat exchange by 63.5% in PCM-filled buildings compared to the reference one. The thickness of PCM is increased from 5 to 10 and 20 cm, and it is found that energy exchange in the second building is less than that in the first building by 4500, 7546 and 11,681 kwh/year at 5, 10, and 20 cm respectively. Although the increase in thickness is less effective for the third building, the amount of energy-saving is equal to 17120, 19835, and 21,215 kwh/year at 5, 10, and 20 cm.
