Comparative cradle to end-of-use embodied carbon analysis of high-rise concrete buildings using volumetric modular and panelized construction

Abstract

Global carbon neutrality targets necessitate significant emissions reductions across industries, with the construction industry playing a crucial role. Construction processes have evolved to address this challenge, from traditional to more efficient modes. Panelized construction (PC) enhances efficiency and resource utilization compared to traditional construction by prefabricating raw materials into standardized components in the factory and transporting them to the site for construction. Volumetric modular construction (VMC) further advances the on-site process introduced by PC, transforming it from traditional construction activities to primarily assembly-based procedures. However, comparative analyses of embodied carbon (EC) between VMC and PC remain limited. It is still to be clarified whether VMC can achieve carbon reductions compared to two-dimensional PC and at which stages, leading to the identification of possible low-carbon pathways. This study addresses this gap by systematically examining and comparing the EC and possible causes of high-rise concrete residential buildings constructed using VMC and PC from cradle to end-of-use, proposing low-carbon recommendations. First, a multi-level framework for measuring and comparing EC was developed to analyze the EC emissions associated with VMC and PC across various temporal and spatial dimensions. Second, the analytical results derived from the framework elucidated which stages of reductions were achieved and explored the causes. Third, the study employed the first high-rise modular residential concrete building with cast-in-situ shear walls in China as the case study. Results indicate that the typical floor in VMC exhibits average EC emissions of 750.2 kg CO2e/m2, compared to 765.51 kg CO2e/m2 for PC, reflecting a 2 % reduction in EC emissions. Despite EC emissions increasing during the transportation stage in VMC due to the larger size and weight of the modules, overall reductions are achieved by minimizing waste in other stages. These findings contribute valuable insights to EC from high-rise VMC and provide a replicable framework for systematic EC comparison across different stages. Results demonstrate that VMC with a higher degree of prefabrication results in lower EC, and transportation strategies significantly impact its effectiveness. The framework also facilitates the integration of VMC into carbon markets, supporting industry-wide carbon reduction initiatives.