The French government has set up thermal regulation policy to minimize building energy consumption and ensure occupant's comfort in residential buildings, named RTAADOM in Reunion Island for "Acoustic, Aeraulic and Thermal Regulation applied to French overseas countries". It is used to design building walls, particularly the insulation materials they are made of, according to the building environment, which is described by four major climatic zones in the island. The present work highlights the potential of using phase change materials (PCM) as a candidate to improve insulation solutions traditionally used to comply with the regulation. The paper focuses on building's indoor temperatures to show that using a PCM can be an excellent solution to improve building thermal behavior in compliance with regulation needs. A reference building based on previous works on the development of a local insulating material is used to run a set of numerical thermal modeling in EnergyPlus. The results show differences between the thermal behavior of the reference building to ones with traditional regulation insulation and with three types of PCM material (a manufactured one and two imagined). Those two lasts were imagined from studies carried out within the framework of the MCP-iBAT FEDER project. The review shows that it is necessary to adapt the PCM properties (phase change temperature and range) to the building environment and uses. The present paper results show that the three PCMs can be used to partly or completely replace an insulation as recommended in the regulation. However, each environment needs a particular PCM configuration to optimize its impact on the building behavior. These results support the need to carry out additional studies to design the PCM material according to the building environment and its uses.