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Updated: October 2020
Autocase recently released a white paper on how to prioritize building investments to help in reducing the spread of COVID-19. It is a summary of the building science literature collected to date on the relationship between Heating, Ventilation and Air-Conditioning (HVAC) systems and the spread of airborne infectious diseases. It represents the latest information in this field and corroborates recommended guidelines to reduce the spread of COVID-19 from the US Centers for Diseases Control and Prevention (CDC), the World Health Organization (WHO), and HVAC industry leaders.
HVAC and COVID-19
Three major aspects of HVAC that can reduce the airborne transmission of airborne diseases are: ventilation, filtration, and relative humidity.
HVAC industry leaders, such as ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) and REHVA (Federation of European Heating, Ventilation and Air-Conditioning Associations), recommend using HVAC to reduce the airborne transmission of COVID-19. Changes to building operations, including the operation of HVAC systems, can reduce airborne exposures. For example, recommended interventions from ASHRAE and REHVA to reduce the airborne transmission of COVID-19, include:
- increased ventilation,
- higher rated/efficient air filters, and
- maintaining the temperature and relative humidity of the building/room within an optimal range.
None of the results are simple and the science is not settled. For example:
- increasing ventilation rates and improving airflow patterns for buildings can reduce the spread of airborne diseases but exceedingly high ventilation rates, based on building- and location-specific factors, may lead to other negative health impacts.
- higher efficiency filters can be used in reducing the spread of airborne diseases. Higher efficiency filters are better suited to removing the smallest particles, but are not guaranteed to capture all particles. They may also lead to higher operational costs in the short-term.
- there is a divide in the research on the recommended range of relative humidity to combat the spread of airborne diseases. The extremes of ~20% and ~80% should not be used as they lead to other negative health impacts.
The disabling of HVAC systems is not a recommended measure from ASHRAE and REHVA to reduce the transmission of COVID-19. Autocase is committed to periodically updating the white paper to include the most recent, peer-reviewed literature.
Using the HVAC & COVID-19 Conclusions
The most important part of the white paper described how Triple Bottom Line Cost Benefit Analysis (TBL-CBA) can be used to value the overall net benefit of these HVAC recommendations and provide a quantitative measure of qualitative considerations into the decision-making process.
Pandemic Building Investment Prioritization
The white paper contains more information on the transmission mechanisms of COVID-19, a case study on how to prioritize health-improving building investments, and a list of dozens of the references used for the research. Please download the white paper and provide us with any feedback or things we’ve missed.