Investigation of HVAC Operation Strategies for Office Buildings During COVID-19 Pandemic

Abstract

To minimize the indoor transmission of contaminants, such as the virus that can lead to COVID-19, buildings must provide the best indoor air quality possible. Controlling indoor air quality is largely achieved by running the building’s HVAC system to dilute any concentration of indoor contaminants. However, doing so has practical downsides on the HVAC operation that are not always quantified in the literature. This paper develops a temporal simulation capability that is used to investigate the indoor virus concentration and operational cost of an HVAC system for two mitigation strategies: 1) supplying 100% outdoor air into the building and 2) using different HVAC filters, including MERV 10, ASHRAE minimum-recommended MERV 13, and highly rated HEPA filtration. These strategies are applied to a hypothetical medium office building consisting of five occupied zones and located in a cold and dry climate. We modeled the building using the Modelica Buildings library and developed new models for HVAC filtration and virus transmission to evaluate COVID-19 scenarios. We show that the ASHRAE-recommended MERV 13 filtration reduces the average virus concentration by about 10% when compared to MERV 10 filtration, with negligible additional operational cost. In contrast, the use of 100% outdoor air or HEPA filtration reduces the average indoor concentration by about an additional 3% compared to MERV 13 filtration, but significantly increases building operational cost. This is due to the significant increase in energy consumption when supplying 100% outdoor air and the higher cost of purchasing a HEPA filter.