Cold formed steel-framed constructions have been strongly disseminated with particular emphasis on the residential sector due to their fast execution, quality control and final cost. However, this construction typology presents a weakness associated with a low thermal inertia and a consequential risk of overheating. The present research addresses the overheating rate reduction of a cold formed steelframed building located in the coastal region of mainland Portugal, a particular environment considering the combination of the high outdoor temperature amplitude and the lack of thermal inertia of such building typology. To overcome this weakness, different phase change materials solutions (PCMs) were incorporated into the partition walls and ceilings of south oriented compartments. Thus, thermal energy storage provided by the PCMs solutions play a crucial role in the indoor thermal regulation of the building by minimizing indoor temperature peaks and amplitude improving indoor thermal comfort with lower energy demand. To optimize the PCM solution in order to reduce the rate of overheating, a hybrid evolutionary algorithm was used in conjunction to the EnergyPlus® simulation engine, adapting a list of parameters. This study was extended to identify the best PCM solution to minimize, in some cases prevent, the overheating risk for different climate applications in Portugal mainland. The results attained reveal the possibility to reduce the overheating risk by up to 89% in highly glazed south faced compartments and 23% in north orientated compartments. In terms of heating energy demand, a reduction of 17% was also attained, triggered by the PCM storage effect.