Life cycle thinking-based energy retrofits evaluation framework for Canadian residences: A Pareto optimization approach

Abstract

Building energy retrofits have been identified as key to realizing climate mitigation goals in Canada. However, retrofit solutions that only produce greenhouse gas emission savings can place economic burdens on residential building owners and hinder the community penetration of building energy retrofitting projects. Therefore, investigating trade-offs between environmental and economic impacts of retrofitting is essential to identify optimal retrofit strategies that can produce emissions savings while delivering economic benefits for the stakeholders. This paper proposes a community-level building energy retrofit evaluation framework for residential buildings. The proposed framework evaluates building energy retrofits using a multi-objective optimization approach that accounts for associated life cycle economic and environmental impacts. Life cycle CO2 emissions were selected as the indicator for environmental performance. The net present value of the cash flows involved in a given retrofit project throughout the project life cycle was selected as the economic performance indicator. Building energy simulation results were combined with economic and environmental impact data to quantify these performance indicators. The performance results were used to identify Pareto-optimal retrofit solutions. The results indicate that retrofitting existing residential buildings can produce considerable emission reductions (up to 245.1 tonCO2eq/residence) and cost savings (up to 12,900 $/residence). Moreover, retrofit packages should prioritize upgrading building envelope insulation and space heating systems. This study introduces a decision support tool for community-level retrofit planners that can account for life cycle environmental and life cycle economic performance of retrofitting while fulfilling capital investment constraints.