Comparing Metrics for Scenario-based Robustness Assessment of Building Performance

To decrease greenhouse gas emissions of the Swiss building stock, effective retrofit strategies are necessary. Due to the long-term operation of buildings, future developments and uncertainties need to be considered, which calls for assessing the robustness of retrofit decisions. Existing studies propose robustness metrics for decisions under deep uncertainty to be coupled with a scenario-based simulation approach. We review these metrics and present a simulation approach that includes current and future operational energy, emissions, and costs. We apply the seven identified metrics to retrofit decisions of a multifamily house located in Zurich, where future scenarios in terms of climate, occupancy, decarbonization, and cost development are included. The metrics are based on different assumptions and positions towards risk. We further find that the discriminatory power is different, confirming the Minimax Regret metric to be most suitable for the building context when looking at individual buildings. For the case study, we find that deep retrofit seems to be a robust decision from an environmental perspective. From a cost perspective, the electrification of the heating system with heat pumps and the installation of PV without a complete envelope retrofit proves to be most robust.