## 1 Introduction  
In Europe, the Deutsche Gesellschaft fur Nachhaltiges Bauen (DGNB, from Germany), the Building Research Establishment Environmental Assessment Method (BREEAM, from the UK), and Leadership in Energy and Environmental Design (LEED, from the US) are the most recognized rating systems [1]. The DGNB places equal emphasis on each of the three classic pillars of sustainability (i.e., the triple bottom line concept), which are expressed through normalized scores: environmental sustainability (22.5%), social sustainability (22.5%), and economy sustainability (22.5%) [2], compared to both BREEAM and LEED, which place more of an emphasis on environmental sustainability (in both schemes, 74.6%), less of an emphasis on social sustainability (16.2% and 18.0, respectively), and a minor or negligible emphasis on economic sustainability (2.3% and 0.82%, respectively) [3]. According to [PERSON] [1], DGNB has a dominant position in Germany and Austria, and BREEAM has a dominant position in the United Kingdom, Slovenia, France, Spain, Lithuania, Belgium, Poland, and the Netherlands. However, the LEED has a strong position in Spain, Turkey, Italy, Sweden, and Finland [1]. Therefore, the LEED was the focus of this study. In this respect, several empirical studies of LEED certified projects were revealed [4; 5; 6; 7; 8; 9]. These studies analyzed different LEED subsystems and versions. It should be noted that, among the many practiced LEED subsystems, such as Existing Buildings: Operations & Maintenance (LEED-EB), Commercial Interiors (LEED-CI), Core and Shell Development (LEED-C&S), LEED Interior Design and Construction for Retail (LEED ID+CRetail), LEED Building Design and Construction for Schools (LEED BD+C Schools), LEED Building Design and Construction for Homes (LEED BD+C Homes), LEED for Neighborhood Development (LEED-ND), and LEED Building Design and Construction for Healthcare (LEED BD+C Healthcare), the LEED for New Construction and Major Renovations (LEED-NC) is one of the most requested rating subsystems [10]. Empirical LEED studies [4; 5; 6; 7; 8; 9] have revealed prevailing strategies and analyzed certification category achievements. The certification achievement is the total number of points that were received by a project in all seven LEED categories (Sustainable Sites [SS], Water Efficiency [WE], Energy and Atmosphere [EA], Materials and Resources [MR], Indoor Environmental Quality [EQ], Innovation in Design [ID], and Regional Priority [RP]) at any certification level (certified, silver, Certified, or platinum) [7]. The category achievement is the number of points that are received by a project per the individual categories, such as SS, WE, EA, MR, EQ, ID, or RP [7]. [PERSON] [4] studied over 2,000 LEED-NC, LEED-CI, LEED-C&S, and LEED-EB certified projects registered as of March 2009 in the U.S., with low LEED certification levels reported by the author. This result means that the analyzed projects were clustered slightly above the lower thresholds of each certification level, with values of 40, 50, 60 and 80, in Certified, silver, Certified, and Platinum certifications, respectively. However, [PERSON] [4] evaluated all types of certified buildings (NC, C&S, and EB) together in one pooling sample without any rigorous statistical analysis. [PERSON] and [PERSON] [5] studied LEED-NCv3 certified projects (1000 pooled samples) in the U.S. Again, low certification levels were reported, while the EA category was noted as a category that moved a project from lower to higher certification levels. This outcome means that the difference between, for example, Silver certified projects and Certified certified projects, was mainly due to high achievements in the EA category in Certified certified projects compared to that of Silver certified projects. However, no significance tests were applied in this study [5]. The empirical evidence of LEED certification with applied significance tests was performed by [PERSON] et al. [6], who analyzed 5340 pooled certified projects of the LEED-NCv2.2.