Analyzing the compliance and correlation of LEED and BREEAM by conducting a criteria-based comparative analysis and evaluating dual-certified projects

Certified green buildings are known to demonstrate high environmental performance; however, it is still not clear where they stand among each other, unless certified by the same body. This study aims to examine the compliance and correlation between the most prominent green building rating systems, LEED and BREEAM. It also estimates how a project would be graded by one system if already certified by the other. Regarding the methodology of the study, the intents of evaluation criteria in the latest versions for new constructions of LEED and BREEAM are analyzed. Commonly addressed and different concerns are determined, and the scales for assigning their award levels are compared. It is observed that they have a high level of compliance because 83% of the environmental concerns are commonly addressed issues. Moreover, it is derived that a dual-certified project aiming to achieve the same award level in both assessments has to display a better performance in BREEAM as it includes a higher number of concerns to be fulfilled. Based on the correlation analyses on twenty dual-certified buildings, the results from the scatter plot diagram, Pearson's Correlation Coefficient (r) and Paired Samples t-Test show that there is a large positive linear correlation and that LEED scores are significantly higher than BREEAM scores. Furthermore, the difference between the averages of LEED and BREEAM scores and the average difference between award levels indicate that if there would be a difference in ratings of dual-certified projects, it would be in favor of LEED by one award level.