Model-driven management of construction carbon footprint

The construction industry is one of the highest contributors to greenhouse gas emissions and there is an increased awareness towards making the industry more sustainable, efficient and environment-friendly. Although there have been significant strides in building energy efficiency through adoption of rating systems and codes, the focus on developing best practices for reducing the carbon-footprint of the construction phase of the life-cycle of a project has been limited. Although the construction phase is short compared to the use phase of a building, the intensity of emissions during this phase is higher and there is an opportunity for improvement through measuring and monitoring the accrual of carbon-footprint during construction. The research question that this thesis explores is how a Building Information Model (BIM) based workflow used with Life Cycle Assessment (LCA) tools can enable contractors and construction managers to measure and track their carbon-footprint. To address this research question, the study presents a model-driven framework together with two case studies validating the carbon footprint management tool for the construction projects. Current practice lacks methods to track carbon footprint of the construction phase since the application of Life Cycle Assessment (LCA) methods has remained primarily limited to design and operation phases of a project. In addition, the current methods heavily rely on user inputs on materials and the state of planned-vs.-actual work-in-progress. The presented framework addresses current inefficiencies by leveraging 4D Building Information Models (BIM) in conjunction with LCA tools to benchmark carbon footprint during pre-construction phases and monitor it during the construction phase. The management framework – built on earned value management concepts – offers metrics to assess and communicate deviations between benchmarked and actual carbon footprint, and facilitates root-cause assessments to minimize performance deviations, and excessive carbon footprints. The two case-studies performed as a proof-of-concept vary in their BIM practices and progress monitoring methods, so a parallel has been drawn between the state of BIM adoption and the opportunity for better carbon-footprint management. The case-studies show that if the framework is used, there is a significant opportunity for reduction in the excess carbon footprint generated at the project level. The deviations are visualized in a timely manner using the BIM-based method which is key to facilitate communication and decision-making for taking required corrective actions. With project teams being able to realize the effect of carbon-footprint, it acts as an incentivizing force to the upstream supply chain to document and provide embodied carbon data for materials and assemblies used in construction because there is an incentive for the contractors to choose a supplier with lower carbon-footprint. Another application of the proposed management framework is for establishing policies requiring adherence to a carbon footprint budget during project tendering. Also, incentivizing contractors to manage their carbon-footprint by establishing best practices by the implementation of emissions cap-and-trade programs has been suggested and discussed