HVAC system energy retrofit for infection risk mitigation - A Multi-Objective Optimization and Multi-Criteria Decision-Making approach

In this study, the energy retrofit of a partial recirculation all-air HVAC system serving a university lecture room located in Naples (South Italy) is analysed. The methodology is based on multi-objective optimization (MOO) and multi-criteria decision-making (MCDM) to find optimal design alternatives and rank them considering the best compromise solutions for two different decision-makers, i.e., public and private stakeholders. The results of the study show that, in the post pandemic era, baseline retrofit scenarios for infection reduction that do not involve installation of inverter devices and automatic dampers cause energy consumption increase from negligible values up to 59%. Contrariwise, baseline retrofit scenarios involving the installation of inverter and automatic dampers cause energy consumption decrease between 5% and 38%. In this last scenario (operation of the air conditioning system with 60% outdoor air + HEPA filter + inverter and automatic dampers), for the implementation of further deep retrofit intervention solutions, there is no agreement between decision-makers on the preferable retrofit solution. In the case of operation of the system with 100% outdoor air + inverter and automatic dampers, for the implementation of deep retrofit intervention solutions, both public and private stakeholders agree on the same deep retrofit solution.