“…In this respect, EN ISO 52120-1:2022 [28] and the previous, recently repealed, EN-15232-1 [29] have introduced a specific methodology for energy savings through the concept of TBM functions [30]. Many studies demonstrate this process improvement, such as [25], which calculates the discounted payback period; [31], which includes a BAC audit tool; [32], which calculates the lighting systems; and [11], which evaluates the savings of the heating systems. Nevertheless, some research has concluded that this method does not provide a reliable estimate of achievable energy savings because it does not take into account other factors, such as building and installation design parameters (e.g., type, dimensions, envelope, air exchanges, settings) and contextual factors (e.g., occupant behaviour, climate zone, latitude, and orientation) [33].…”