Phase change materials (PCMs) have proven to be a valid strategy in case of passive energy refurbishment of the existing building stock. Over the years, in fact, researchers have investigated the possibility of their integration within different components of the building envelope, such as walls, roofs, and floors, to increase the overall building thermal inertia and thus reduce the energy demand for heating and/or cooling. Many studies were focused, either experimentally or numerically, on the optimization of the PCM location and of its thermo-physical properties to maximise their effect and thus reduce the energy demand for cooling or heating. However, in case of existing building refurbishment the amount of PCM that can be integrated is usually rather limited and their location constrained in order to avoid any design alteration of the building, which is fundamental when dealing with historic buildings whose aesthetical preservation is of outmost importance. Nevertheless, this inevitably leads to reduced thermal storage capacity that can be added to a building component and with special regard to the addition of PCM within plasters, suitable mass ratios do not usually exceed 20%. In some circumstances, therefore, the application of PCM might seem not convenient in achieving a reduction of the energy demand, either for cooling or heating. Based on the know-how gained over the past years through both experimental and numerical investigations on granular PCMs embedded in lime-based plasters applied on exterior walls, some of the main limits of such application were assessed. This was done differentiating the analysis according to the building envelope properties, hence the variety of their construction period, the thickness and thermo-physical properties of their materials and the outdoor weather conditions.