Utilization of phase change materials (PCMs) in building enclosures as thermal energy storage systems (TES) has become a re-appearing topic within the research community in recent years. PCMs represent an innovative solution that can contribute to the improvement of energy efficiency and thermal performance of buildings. This paper aims to present results of experimental investigations regarding the effectiveness and differences of PCM positioning within building enclosures in terms of energy performance and thermal comfort. The experiments are conducted in a laboratory setting, more specifically in an environmental test apparatus, that allows for comparative testing of interior thermal and hygrothermal performance under different exterior climate scenarios. The paper discusses the experimental setup, the employed analysis methods, and findings of effects for different PCM positions in exterior wall configurations. It explores the observed differences and discusses potential opportunities that exist in regards to reducing overall thermal losses in enclosures and improving thermal comfort in interior spaces.