LEED-CI v4 Projects in Terms of Life Cycle Assessment in Manhattan, New York City: A Case Study

Abstract

Over the last decade, it has been clearly shown that the same achievements in Leadership in Energy and Environmental Design (LEED) projects can lead to different life cycle assessments (LCAs). However, the problem of contradictory achievements in LEED and LCA has not yet been resolved. This study aimed to identify and evaluate different strategies for LEED projects using LCAs. Thirty-nine LEED projects with the same characteristics—location and transportation, rating system, rating version, certification level, and space type—were collected and sorted by their energy and atmosphere (EA) category, “optimize energy performance” credit (EAc6) achievement into three equal groups (EALow, EAMedium, and EAHigh, where each group includes 13 LEED projects) to minimize the influence of uncontrolled factors on the LEED project strategy. The author focused on two extreme groups with very different EAc6 credit scores: EALow (13 projects) and EAHigh (13 projects). The groups were compared across LEED categories and credits. Wilcoxon–Mann–Whitney and Cliff’s δ test results showed that the EALow and EAHigh groups are associated with high/low achievements in materials-related credits such as “interiors life cycle impact reduction”, “building product disclosure and optimization—material ingredients”, and “low-emitting materials”. As a result, the EALow and EAHigh groups were reclassified into EnergyLow–MaterialsHigh and Energyhigh–MaterialsLow certification strategy groups. In this context, LCAs were used to assess the differences between the two strategies. The results showed that if natural gas was used for operational energy (OE), the EnergyHigh–MaterialsLow strategy showed lower environmental damage compared to the EnergyLow–MaterialsHigh strategy (p = 0.0635); meanwhile, if photovoltaic energy was used for OE, the EnergyLow–MaterialsHigh strategy showed lower environmental damage compared to the EnergyHigh–MaterialsLow strategy (p = 0.0036). The author recommends using the LEED protocol and the LCA method in parallel to better reflect the environmental impact of different certification strategies.