Life cycle embodied energy analysis of higher education buildings: A comparison between different LCI methodologies

Nearly half of the global annual energy supply is consumed by the building construction sector, indicating an enormous potential to minimize the carbon footprint. During its life cycle, a building consumes energy in the form of embodied and operational energy. Embodied energy (EE) is expended in processes during construction (ex: extraction of raw material, transportation, manufacturing, etc.). Operating energy (OE) is spent on operating and maintaining the building to ensure occupant comfort. Unlike OE, the methods used to calculate EE are complex, unstandardized, and time-consuming. Each EE calculation method utilizes different sources of data and system boundary definitions, therefore making it difficult to comprehensively evaluate building life cycle energy (LCE). Literature suggests that the disaggregated input-output based hybrid (IOH) approach is more accurate, complete, and reliable in comparison to the other EE calculation methods. In this study, we examine the EE-OE relationship by calculating EE factors for a newly constructed and renovated educational building. Next, we also compare the variation in EE factors across different life cycle inventory (LCI) methods (process-based, aggregated IOH, and disaggregated IOH). The results of this study indicate that using different LCI techniques to calculate EE causes massive variations in EE factors, which represent the EE expense of saving one unit of OE. The findings of our study and literature review show that the process-based approach underestimates EE, therefore the values of EE factors calculated using this approach need to be interpreted with caution. These results further elucidate the importance of standardizing the EE calculation method.