System-Based Greenhouse Gas Emission Analysis of Off-Site Prefabrication: A Comparative Study on Residential Projects

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The construction industry, particularly in high-rise residential developments and off-site prefabrication, plays a significant role in greenhouse gas (GHG) emissions—accounting for approximately 30% of total emissions worldwide. This study compares traditional construction methods with off-site prefabrication, focusing on emissions generated during key stages of the latter. It further explores the differences between two predominant prefabrication systems—concrete and steel—commonly used in Chinese residential construction. Through the analysis of four case studies, the study aims to illustrate the methodology and offer practical insights for construction management.

In densely populated countries such as China, high-rise residential buildings are a common solution due to limited land availability and rising land costs in major cities like Beijing. In 2022, residential buildings made up 67.36% of China's completed construction area, dwarfing the percentages for factories (12.2%), services (7.11%), and offices (4.77%) according to the China Statistical Yearbook.

As sustainability becomes a core focus, the construction industry seeks to curb its GHG output, driven by its substantial energy consumption (40%) and emissions (30%). Previous research, such as that by Kibert, emphasizes sustainable construction practices rooted in ecological efficiency. However, projections by Huovila et al. suggest that emissions could double in the coming decades due to urbanization and sector inefficiencies—making emission reduction in residential projects increasingly urgent.

Most existing research emphasizes the operational stage of a building’s life cycle, with limited attention to emissions during construction. Guggemos and Horvath noted that operational emissions represent only 12% of a building’s overall environmental impact. While some studies (e.g., Cole, González, and Navarro) have examined materials like timber, steel, and concrete for their environmental footprint, others have highlighted the importance of using recycled materials to reduce embodied emissions. Yan et al., for instance, proposed a quantitative model to calculate GHG emissions during construction.

Off-site prefabrication has emerged as a promising method for minimizing construction-related emissions. Aye et al. found that material selection can have a greater impact on environmental performance than construction method changes. Similarly, Jaillon and Poon’s review of Hong Kong’s prefabricated housing suggested that prefabrication’s effectiveness depends on both volume and component type. However, as Mao et al. pointed out, there remains a lack of detailed studies evaluating prefabrication’s GHG output—highlighting the need for further research.

In China, the three primary prefabricated structural systems are concrete, steel, and timber. Since 2016, the government has strongly promoted prefabricated concrete and steel structures. Concrete, with abundant raw material sources, has become the mainstay in both industrial and residential applications. Although steel structures are versatile, they represent a smaller market share due to higher costs. Timber systems, while environmentally favorable, are limited by material shortages and are typically used in low-rise buildings such as schools and kindergartens.

Given that high-rise residential projects significantly contribute to construction emissions, the choice of building method and structure is critical. This paper makes three primary contributions:

It quantifies life-cycle GHG emissions across different construction systems, evaluating prefabrication’s effectiveness in reducing emissions.

It compares two widely used prefabrication systems—concrete and steel—within Chinese residential construction.

It presents four case studies to validate the methodology and provide managerial recommendations.