Incorporation of Embodied Energy into Building Energy-Efficiency Codes: A Pathway to Life-Cycle Net-Zero Energy Building in Australia

Abstract

This thesis aims to demonstrate the importance of incorporating embodied energy into the building energy efficiency regulations (BEERs) of Australia. This study commences with conducting a comprehensive literature review of studies that employ a life cycle energy assessment (LCEA) approach in evaluating the total energy performance of buildings. As a result, sixty-six studies have been analysed with respect to the methodological approaches taken for defining system boundary conditions. It is shown that the current trend of LCEA application in residential buildings suffers from significant inaccuracies due to incomplete definitions of system boundary conditions. The findings form the base for developing a comprehensive framework through which the system boundary definition for calculations of embodied and operational energies can be standardized. Further, this study quantifies the significance of embodied energy associated with Australian BEERs by assessing the total life cycle energy performance of more than 2,300 design scenarios of a residential building – reflecting a range of performance from standard 6-star buildings to highly energy-efficient buildings. The results revealed that the proportion of embodied energy significantly increases from 20–40% to 50–75% in transitioning from standard 6.0-star buildings to highly energy-efficient buildings. This finding underlines the necessity of including the embodied energy impacts into the BEERs when moving towards energy neutrality in the residential building sector. This study also puts forward a comprehensive framework based on the findings of a literature review examination that enables incorporating embodied energy into BEERs by standardising system boundary definitions in LCEA analysis. The framework developed in the research consists of six distinctive dimensions i.e., temporal, physical, methodological, hypothetical, spatial, and functional. These dimensions encapsulate 15 components collectively, including ‘stages of building life cycle’, ‘building components and systems’, ‘elements beyond building scales’, ‘method for assessment of embodied energy’, ‘background database for embodied energy assessment’, ‘type of energy’, ‘unit of measurement’, ‘parameters contributing to operational energy assessment’, ‘method for assessment of operational energy’, ‘assumptions’, ‘building lifespan’, ‘climate’, ‘building site location’, ‘building type’, and ‘density’. The proposed framework possesses two key characteristics. First, its application facilitates defining the conditions of a system boundary within a transparent context. This consequently leads to improved reliability of obtained LCEA results for decision-making purposes since any particular conditions (e.g., truncation or assumption) are considered in establishing the boundaries of a system. Second, the use of a framework will also provide a meaningful basis for cross comparison of cases within a global context, which allows identification of best practices for the design of buildings with low life-cycle energy use. The study application of the proposed framework has been demonstrated by analysing the LCEA performance of a case study building in Adelaide and cross comparing the results with a case study building retrieved from literature and located in Melbourne. The results have indicated the capability of the framework for maintaining transparency in establishing a system boundary in an LCEA analysis, as well as a standardized basis for cross-comparison of cases. The study concludes with recommending potential measures for future developments of Australian BEERs. In summary, the implications of this research underscore the need for future generations of Australian BEERs to consider reduction of buildings’ embodied energy impacts as a requirement for realizing net-zero energy or carbon in the built environment. The implementation of this approach can positively contribute to reducing the use of energy (or carbon)-intensive products in the residential building sector, limiting their impacts on national carbon emissions while encouraging cleaner production of construction products. On a broader scale, this study contributes to improving the current procedures for standardisation of LCEA analysis by proposing a framework that introduces six distinctive dimensions. The outcomes of this research are expected to assist policymakers with including embodied energy into current BEERs.