Green building concept plays a fundamental role in reducing the use of resources and the impacts on human health and environment, during the whole building life cycle. Therefore, a method to measure the building sustainability rate is crucial for comparing various alternatives in terms of use of different materials, energy resources, production processes to reduce energy consumption and environmental impacts. Many protocols have been proposed to perform buildings’ sustainability evaluation; however, different operators applying these certification tools might need to make hypotheses, even different from each other, to complete the whole procedure. Hence, this work aims to evaluate whether and how the hypotheses formulated by each operator can influence the final certification level. To this end, a Round Robin Test among international partners was performed using different versions of LEED sustainability protocol to the same building with the same boundary conditions, comparing and analyzing the results provided by the participants. The final aim was to identify which issues have more influence on the final performance rate, giving to the users a deeper knowledge of the aspects included in these procedures. The results showed the potential of these building environmental certification systems, capable of offering a transversal level of environmental sustainability.