Maraqa, M. J., Sacks, R. & Spatari, S. (2023). Role of workflow in reducing life cycle energy consumption in construction. Proceedings of the 31 st Annual Conference of the International Group for Lean Construction (IGLC31), 474–485. doi.org/10.24928/2023/0171 Lean and Green 474 ROLE OF WORK FLOW IN REDUCING LIFE CYCLE ENERGY CONSUMPTION IN CONSTRUCTION Musab Jamal Maraqa 1 , Rafael Sacks 2 , and Sabrina Spatari 3 ABSTRACT Lean construction aims to improve the construction industry by focusing on flow and value and eliminating waste. Reducing waste can also meet environmental goals by reducing greenhouse gas emissions (GHGs) and improving environmental performance. Many green building rating systems have emerged over the last three decades as instruments to incentivize the production of buildings that minimize the impact on the environment and human health. However, those approaches are oriented toward the end product only, leaving builders without guidelines on effective processes to reduce operational waste. This research reviews and evaluates opportunities to mitigate GHGs and improve environmental performance through lean construction. It measures the effects of lean principles on reducing GHGs by improving the flow. Case study research was used to measure the quantity of diesel used for heating two construction projects in a cold climate; one is a traditionally managed project and the other is managed using Virtual Design and Construction (VDC) and the Last Planner System (LPS). Results show that the floor cycle time reduced from 189 days to 115 days in the lean-VDC project, a reduction of 64%. Also, the total embodied GHGs reduced from 1,037-tons CO2e to 629-tons CO2e, a reduction of 408-tons CO2e. KEYWORDS Lean construction, life cycle assessment (LCA), energy consumption, flow, transformation- flow-value INTRODUCTION The construction industry is responsible for a significant amount of energy consumption and greenhouse gas emissions (GHGs) (IEA, 2019). Construction waste in Israel represents major source of waste. It contains different construction materials like steel, blocks, tiles, plastic materials, gravel, and soil (Katz and Baum, 2011). In 2016, the amount of construction waste rose to 7.5 million tons, (Tal, 2016). Lean construction aims to eliminate different types of wastes by focusing on flow and value. Waste in construction, understood from the lean point of view, comprises not only physical waste but any exhaustion of resources that does not satisfied value to the customer (Womack and Jones, 2003). Bølviken et al., (2014) studied the wastes in construction from the Transformation-Flow-Value theory (TFV) point of view. They proposed a definition of waste as the use of more inputs than needed and unwanted output. This definition can cover aspects 1 Ph.D. Graduate Student, Faculty of Civil and Environmental Engineering, Technion - Israel Institute of Technology, Haifa, Israel, +972 59 8218363, musab_maraqa@hotmail.com, orcid.org/0000-0002- 7756- 2787. 2 Professor, Faculty of Civil and Environmental Engineering, Technion - Israel Institute of Technology, Haifa, Israel, +972 4 829 3190, cvsacks@technion.ac.il, orcid.org/0000-0001-9427-5053. 3 Associate Professor, Faculty of Civil and Environmental Engineering, Technion - Israel Institute of Technology, Haifa, Israel, +972 54 668 4373, ssabrina@technion.ac.il, orcid.org/0000-0001-7243- 9993.