Carbon emissions of cast-in-place and prefabricated buildings: A comparative analysis and carbon reduction strategy

Abstract

Prefabricated buildings are increasingly advocated for their benefits, which include a shortened construction period, cost-efficiency, and enhanced resource utilization. However, the comparison between prefabricated and cast-in-place buildings on life-cycle carbon emissions is still insufficient. This study assesses and analyses the life cycle carbon emission of both types of structures and achieves carbon reduction strategies at various life cycle stages from actual cases. The analysis reveals that for both modular and cast-in-place buildings, the materials contributing the most to carbon emissions are concrete blocks, concrete, steel rebar, formwork, and wall plaster. In addition, the formwork in prefabricated buildings constitutes nearly half of the total carbon emissions during the construction stage compared to cast-in-place structures. In the maintenance phase, cast-in-place buildings are more low-carbon than prefabricated buildings because the insulation can be replaced. During the dismantling stage, carbon emissions from prefabricated buildings are approximately 11.31% lower than those from cast-in-place structures. The study also introduces several carbon reduction measures, for example, substantial emission reductions can be attained by substituting ordinary Portland cement with new dry process cement, employing RRAC concrete over regular concrete, utilizing lightweight aggregate concrete blocks instead of aerated concrete blocks, and opting for recycled steel. Regarding the operational phase, the implementation of solar photovoltaic panels on building rooftops has been proven to effectively curtail carbon emissions.