The main scope of this thesis is to highlight how the variation of one of the most widespread rating systems for evaluating building sustainability (LEED protocol) and the update of the energy standard ASHRAE 90.1 impact on building design. The analysis, carried out on an existing building located in Turin that recently underwent a major renovation, aims to determine whether a building, previously recognized as performant, sustainable and certified at level “Gold” under LEED v4, can still be considered eligible for certification based on newer and more stringent version (LEED v5). The investigation focuses on the energy performance of the building and was conducted by means of IESVE.