This article conducted a comprehensive study on a three-story residential building in Yazd, Iran, which was meticulously modeled using DesignBuilder. The primary objective was to investigate the impact of BioPCMs (Bio Phase Change Materials), which are environmentally friendly materials, on the building’s thermal performance. For this purpose, BioPCM® M182/Q21 was selected due to its effectiveness in enhancing energy efficiency. The study involved a practical comparison of the building’s energy consumption under three scenarios. The first scenario represented the baseline condition where no PCM was used. The second scenario incorporated PCM into the external walls, while the third scenario extended the use of PCM to both the external and internal walls. In the second scenario, where PCM was applied only to the external walls, there was a 9% reduction in annual energy consumption. The third scenario, which utilized PCM in both the external and internal walls, resulted in a reduction of 15.5% in annual energy consumption. Additionally, when PCM was used in both the external and internal walls, the total energy consumption for cooling and heating the building decreased by 5.4% and 18.9%, respectively.