Assessment of global warming potential from on-site construction processes (module A5): a pilot building case study

The building construction industry is under tremendous pressure to cut down on greenhouse gas (GHG) emissions as upfront embodied carbon emissions are substantial contributors to the carbon footprint of the built environment. The embodied carbon emissions generated at the construction and installation stages of buildings driven by major and ancillary material flows as well as heavy equipment remain insufficiently examined at the micro levels of the construction process. To fill this gap, we integrated whole-building life cycle assessment (WBLCA) with building information modeling (BIM) using the Industry Foundation Classes (IFC) standard; then, we evaluated the global warming potential (GWP) for a building case study at various construction levels in alignment with the framework of the level 2 life cycle carbon standard (EN 15804+A1/+A2) from the cradle-to-gate (option module) perspective. The WBLCA was performed using the One Click LCA tool, where the data were calculated from the structural scope of the work and material-related inputs were obtained from verified environmental product declarations. The results indicate that the total emissions from the building case study account for a total GWP of 11,41,970 kg of CO 2 e, of which the production stage of building materials (modules A1–A3) accounts for 83.98%, construction and installation stages (module A5) contribute to 11.43%, and transportation (module A4) accounts for approximately 3%. Moreover, at different construction levels, the contributions of modules A1–A3 vary from 84.9% to 90.4%, while those of the construction phase (module A5) vary from 7% to 11%, in which the machinery hours have the highest impact on the GWP. Hence, the proposed methodology can effectively help quantify the environmental impacts of various construction processes and can potentially serve as a tool for contractors to reduce material wastage while enabling selection of appropriate equipment as per the site scenario and scope of work.