Implications of Prefabrication for the Life Cycle Carbon Emissions of High-Rise Buildings in High-Density Urban Environment

Buildings worldwide contribute to around one third of carbon emissions. With the rapid urbanization process, high-rise buildings are almost the norm in high-density cities. Prefabrication will help not only reduce the carbon footprint of materials and products, but improve the efficiency of construction processes and quality of constructed facilities which should lead to substantial carbon reductions over the life cycle of the building. However, there is no consistent method of estimating life cycle carbon emissions from prefabricated buildings. The aim of this paper is to examine the implications of prefabrication for high-rise buildings' life cycle carbon emissions (LCCa) in high-density urban environment. The research was carried out through the combination of a critical literature review, a systems survey of previous studies, and a case study with a typical high-rise building in Hong Kong. The review results suggest that, despite the burgeoning studies of life cycle carbon, inconsistent boundaries of life cycle exist with underexplored direct and indirect implications of prefabrication for carbon emissions. A systems framework of methodology is developed for examining the carbon emissions of high-rise buildings and the implications of prefabrication for the production and building process. This framework, for the first time in the life cycle literature, brings forward a multi-dimensional life cycle carbon methodology including temporal, spatial, functional and methodological variables. The case study results uncover carbon emission intensive components of the building and carbon emission intensive processes in the building's life cycle. Several prefabrication scenarios are subsequently presented for reducing the LCCa of high-rise buildings in high-density urban environment, highlighting the aspects of utilizing low-carbon materials and adopting innovative design features.