# An Investigation of the Selection of LEED Version 4 Credits for Sustainable Building Projects
## 4 Results
The results for the first group, comparing LEED Certificate and LEED Silver projects (\(n\) = 50), indicate that LEED Silver projects generally have nine more credits than those at the certificate level, namely, INc1 (innovation), LTc4 (credit surrounding density and diverse uses), EAc3 (advanced energy metering), IEQC1 (enhanced IAQ strategies), IEQC3 (construction IAQ management plan), IPC1 (integrative process), SSc1 (site assessment), SSc3 (open space), and SSc4 (rainwater management). Only the INc1 credit has a medium effect size difference, however, which suggests that innovative solutions are seldom achieved in the LEED Certified projects. Comparing the results for the LEED Silver and LEED Gold projects, the LEED Gold projects implemented 14 additional credits, namely, LTc3 (credit high priority site), LTc4 (credit surrounding density and diverse uses), LTc5 (credit access to quality transit), LTc6 (credit bicycle facilities), LTc7 (credit reduced parking footprint), LTc8 (credit green vehicles), WEc3 (cooling tower water use), WEc2 (indoor water use reduction), EAc1 (enhanced commissioning), EAc5 (renewable energy production), EAc2 (optimize energy performance), MRc1 (building life-cycle impact reduction), INc1 (innovation), and SSc3 (open space). In particular, the LTc4 (surrounding density and diverse uses) and LTc5 (access to quality transit) credits have a medium effect size difference; both of these credits are usually achieved when the project is located in an urban area with high population density and many surrounding services. This suggests that project location factors have a major effect on achieving LEED Gold or LEED Platinum certification. For the highest-level comparison, LEED Gold and LEED Platinum projects, the results of the analysis reveal that the LEED Platinum projects achieved additional 14 credits, namely, EAc2 (optimize energy performance), MRc1 (building life-cycle impact reduction), MRc3 (building product disclosure and optimization--sourcing of raw materials), IEQC5 (thermal comfort), IEQC6 (interior lighting), SSc4 (rainwater management), SSC6 (light pollution reduction), EAc1 (enhanced commissioning), EAc3 (advanced energy metering), EAc5 (renewable energy production), EAc7 (green power and carbon offsets), INc1 (innovation), WEc1 (outdoor water use reduction), and WEc2 (indoor water use reduction). Of these, MRc1 (building life-cycle impact reduction), MRc3 (building product disclosure and optimization--sourcing of raw materials), IEQC6 (interior lighting), SSc4 (rainwater management), IEQC5 (thermal comfort), EAc7 (green power and carbon offsets), EAc1 (enhanced commissioning), and EAc4 (enhanced refrigerant management) credits had a medium effect size, and EAc7 (green power and carbon offsets) had a large effect size. This indicates that the indoor air quality and relevant materials credits were only popular among those implementing LEED Platinum projects. The LEED Platinum certified projects also had outstanding energy savings compared with the other certificate levels of LEED. The on-site renewable energy option is often considered as the last points in LEED Platinum projects only. It is also interesting to note the additional effort needed to move up from the LEED Gold to LEED Platinum certificate; the 20-point difference between these two groups is twice that of the other transitions, where the difference is only 10 points. The results of the association rule mining (Table 4) revealed 442 strong association rules that exceeded the minimum support threshold of 0.4 and reliability = 0.7. Arranging these in order of \"support\" and \"confidence,\" eight rules were chosen by eliminating rules with a lift value of less than 1. Among these, the most important was the participation of a LEED Accredited Professional (AP) in the project (INc2), which affected the results of the credits IEQC3 (construction IAQ management plan), LTc2 (sensitive land protection), and MRc5 (construction and demolition waste management).