Optimizing total factor carbon (TFC) of high-rise modular buildings

Abstract

Modular integrated construction (MiC) is a transformative approach that enhances construction quality, safety, productivity, and sustainability. Although carbon reduction research in MiC is growing, stakeholders face challenges in evaluating the effectiveness of decarbonization strategies and determining their alignment with sustainability goals under resource constraints. This study addresses this critical gap by proposing an innovative total factor carbon (TFC) metric considering total-factor resource constraints (e.g., materials, cost, energy, time). It can rapidly assess cross-case decarbonization strategies during the cradle-to-the-end-of-construction stage. An environmental data envelopment analysis (DEA) model was developed to measure the TFC. It was followed by an enhanced decision-making trial and evaluation laboratory-interpretive structural model (DEMATEL-ISM) to analyze the complex interrelationships among 43 architecture, engineering, and construction (AEC) factors. A multi-dimensional analytical framework was developed to evaluate these factors from temporal (evolution, lifecycle stages), spatial (physical environment, building elements), and axiological (value-driven priorities, stakeholder involvements) perspectives. Scenario analyses of two representative MiC cases (with different structural systems and locations) examined 798 carbon reduction strategies from material, transport, and energy aspects. The results highlight the great importance of the design stage in achieving TFC optimization and project sustainability outcomes. The most effective decarbonization pathways under assumed scenarios include adopting low-carbon materials, shipping with new energy vehicles (NEVs), and transitioning to renewables. The proposed TFC offers industry practitioners and policymakers a decision-support tool for advancing sustainable MiC implementation. The findings will support developing comprehensive guidelines (e.g., roadmaps for decarbonization), incentives (e.g., subsidies or grants), and technical standards (e.g., low-carbon design code).