A Methodological Framework for Life Cycle Sustainability Assessment of Construction Projects Incorporating TBL and Decoupling Principles

The triple bottom line (TBL) principle encompasses the idea of continued economic and social well-being with minimal or reduced environmental pressure. However, in construction projects, the integration of social, economic, and environmental dimensions from the TBL perspective remains challenging. Green building rating tools/schemes, such as Green Rating for Integrated Habitat Assessment (GRIHA), Leadership in Energy and Environment Design (LEED), Building Research Establishment Environment Assessment (BREEAM), and their criteria, which serve as a yardstick in ensuring sustainability based practices and outcomes, are also left wanting. These green building rating tools/schemes not only fail to comprehensively evaluate the three dimensions (social, economic, and environment) and interaction therewith, but also lack in capturing a life cycle approach towards sustainability. Therefore, this study intends to address the aforementioned challenges. The first part of this study presents the concept of sustainable construction as a system of well-being decoupling and impact decoupling. Findings in the first part of this study provide a rationale for developing a methodological framework that not only encapsulates a TBL based life cycle approach to sustainability assessment in construction, but also evaluates interactions among social and economic well-being, and environmental pressure. In methodological framework development, two decoupling indices were developed, namely, the phase well-being decoupling index (PWBDI K ) and phase impact decoupling index (PIDI K ). PWBDI K and PIDI K support the evaluation of interdependence among social and economic well-being, and the environmental pressure associated with construction projects in different life cycle phases. The calculation underpinning the proposed framework was illustrated using three hypothetical cases by adopting criteria from GRIHA Precertification and GRIHA v.2019 schemes. The results of these cases depict how the interactions among different dimensions (social, economic, and environment) vary as they move from one phase to another phase in a life cycle. The methodological framework developed in this study can be tailored to suit the sustainability assessment requirements for different phases and typologies of construction in the future.