The building's energy consumption represents ca. 40% of the total energy consumption and ca. 20% of the CO2 emissions. With the improvement of new construction's efficiency the part of equipment's energy consumption increase more and more compared to the total building energy consumption. This article proposes to study a new approach in building's systems Fault Detection and Diagnosis (FDD), so as to provide an FDD tool intuitive for every operator of the maintenance staff whatever of their qualifications. This new approach using multivariate statistic method provides easily understanding outputs allowing a quick comprehension of the equipment's fault by building maintenance staff. Thereby the number of unsolved problems can be minimized and the intervention time considerably reduced, avoiding unexpected energy consumption and equipment's prematureobsolescence.