Analysis of strategies to meet ASHRAE S241 infectious aerosol control targets by space type and region using EnergyPlus™ simulations

Professional organizations have proposed new voluntary standards for controlling infectious aerosols, such as ASHRAE Standard 241 (S241) which defines equivalent clean air targets for a range of space types that can be achieved through combinations of ventilation and air cleaning technologies. This paper analyzes clean air strategies across four key space types (offices, classrooms, restaurant dining areas, and healthcare waiting rooms) and seven climate zones through EnergyPlus™ building simulations. The strategies include increasing outdoor air ventilation; improving filtration or adding germicidal ultraviolet (GUV) in the central heating, ventilation, and air-conditioning (HVAC) systems; or using portable air cleaners (PACs), upper room GUV, or whole room GUV. Equivalent clean air delivery, energy use, and comfort metrics for each strategy are compared to baseline building operations using ASHRAE Standard 62.1 or 170 ventilation. The results show that strategies applying single measures can meet S241 targets for offices with minimal impacts on energy and comfort, while either upper room GUV systems or combinations of measures such as MERV 13 HVAC filtration with PACs are needed to meet S241 for classrooms. The dining area and healthcare waiting room targets cannot be met when assuming design occupancy and MS2 (bacteriophage specified by S241 for air cleaner testing) as the challenge agent, even with multiple measures. This paper provides valuable considerations when designing strategies to meet S241 for a range of spaces and scenarios.