This paper presents a comprehensive review of the integration of phase change materials (PCMs) in building walls. The integration of PCMs in building envelopes is a promising approach to enhance the thermal energy storage capacity of buildings, thereby reducing energy consumption and improving thermal comfort. PCMs absorb heat during phase change from solid to liquid and release it during phase change from liquid to solid, allowing for efficient thermal energy storage. The paper discusses various physical considerations, phase change theory, and the properties of different PCM types, including organic and inorganic materials. It also covers PCM containment methods such as impregnation, micro-encapsulation, and shape-stabilized PCMs. The paper reviews experimental and numerical studies on PCM integration in building walls, highlighting the importance of accurate measurement techniques for evaluating PCM performance. The review also addresses the challenges associated with PCM integration, including thermal conductivity, supercooling, and leakage. While PCMs show potential for reducing energy demand, further research is needed to fully assess their effectiveness in real-world applications. The paper concludes that systematic evaluation of PCM integration in building structures, particularly under real-use conditions, is essential for optimizing their performance and ensuring their practical implementation.This paper presents a comprehensive review of the integration of phase change materials (PCMs) in building walls. The integration of PCMs in building envelopes is a promising approach to enhance the thermal energy storage capacity of buildings, thereby reducing energy consumption and improving thermal comfort. PCMs absorb heat during phase change from solid to liquid and release it during phase change from liquid to solid, allowing for efficient thermal energy storage. The paper discusses various physical considerations, phase change theory, and the properties of different PCM types, including organic and inorganic materials. It also covers PCM containment methods such as impregnation, micro-encapsulation, and shape-stabilized PCMs. The paper reviews experimental and numerical studies on PCM integration in building walls, highlighting the importance of accurate measurement techniques for evaluating PCM performance. The review also addresses the challenges associated with PCM integration, including thermal conductivity, supercooling, and leakage. While PCMs show potential for reducing energy demand, further research is needed to fully assess their effectiveness in real-world applications. The paper concludes that systematic evaluation of PCM integration in building structures, particularly under real-use conditions, is essential for optimizing their performance and ensuring their practical implementation.