CH-24-C080 - Energy Implications of Different Strategies to Meet Equivalent Clean Air Requirements for Commercial and Educational Spaces

In June 2023, ASHRAE published standard 241, the first airborne infection risk mitigation standard for buildings, bringing numerous benefits to occupants and promoting healthier indoor environments. One of the key breakthroughs of the standard is the creation of a new IAQ target that is defined in terms of equivalent clean airflow per occupant (ECAi/occupant) for 25 space types. The targets range from 30 to 90 ECAi cfm/occupant and can be achieved using one or multiple strategies including limiting occupancy and increasing outdoor air, air filtration, and disinfection that is demonstrated to be safe and effective. Different engineering controls have different contribution to ECAi and different impacts on energy consumption and carbon emissions. We considered outdoor air rates using ASHRAE standard 62.1 prescriptive (ventilation rate procedure, VRP) and performancebased (indoor air quality procedure, IAQP) approach, energy recovery ventilation, mechanical filtration (MERV 7, 11, and 13), in-room air cleaners, and UVGI disinfection for commercial and educational facilities in 15 different ASHRAE climate zones. We repeated the analysis to explore the impact of high outdoor air pollution events such as wildfires on the proposed strategies. Although wildfire smoke contains multiple contaminants, this analysis focuses on controlling exposure to PM2.5. For each scenario, we used the equivalent clean air calculator spreadsheet provided by standard 241 to calculate ECAi, and we used large-scale simulation of prototypical building energy models to calculate the resulting energy consumption for different combination of strategies. Then, we calculated the operating and installed costs for the different strategies. Keeping outside air to a minimum using the IAQP and using a combination of air filtration and disinfection proved to be the least energy intensive strategy in the considered climate zones to meet the required ECAi. This is also true in wildfire events where outside air needs to be minimized while keeping positive pressure in the space and using high MERV filters to clean recirculated air.