Assessing the effectiveness of building retrofits in reducing GHG emissions: A Canadian school case study

Abstract

This paper investigates the impact of energy retrofits on life cycle greenhouse gas (GHG) emissions across different electricity grid profiles in Montreal, Ottawa, and Halifax, using an existing school building as a case study. Using DesignBuilder for energy simulations and OneClick LCA for GHG emissions estimation, this study evaluates whether the reduction in the operational emission achieved by energy savings from retrofits can outweigh the increased embodied emissions from new envelope materials and equipment. In Montreal and Ottawa, where electricity is mainly generated from renewables and non-fossil fuels, retrofits involving electric heating and envelope improvements could decrease life cycle GHG emissions by up to 75 %. However, if the building initially used electric heating, the retrofits led to an increase in life cycle carbon emissions by 170 % in Montreal and 56 % in Ottawa, respectively, due to the embodied emissions of retrofit materials and equipment. In Halifax, where the electricity grid relies heavily on fossil fuels, all retrofit scenarios showed a positive impact on GHG reductions. Enhancing the building envelope and transitioning from natural gas to electric heating slightly reduced total emissions by 4 %, but retaining natural gas heating decreased the total life cycle GHG emissions by 27 %. This study emphasizes the importance of a comprehensive life cycle assessment in developing policies for achieving carbon neutrality. It demonstrates that the effectiveness of retrofits in reducing GHG emissions significantly depends on the local energy grid, suggesting tailored approaches based on regional energy profiles to optimize emission reductions and energy efficiency.