How to Increase Ventilation for Reduced Viral (COVID-19) Transmission
In a previous post I mentioned that increased ventilation can be part of an overall HVAC strategy of mitigating COVID-19 transmission as buildings are re-opened to the public. Put simply, by increasing the amount of outside air coming into your building, we can replace the indoor air more often with fresh air, which typically will have a much smaller concentration of potential virus particles.
A client recently asked for more detail on how to actually implement this in real life for their office building portfolio.
Specific recommendations for increasing outside air are as follows. Most of these can be implemented through the building automation system (BAS) or the equipment controllers, if BAS is not available:
1. Run ventilation systems continuously, or at least increase the hours of ventilation operation (done by disabling unoccupied modes or adjusting schedules). Note that this measure can increase utility costs significantly, and should be considered temporary!
2. If available, review past building trend data to verify that equipment can handle increased ventilation loads during peak seasons. For example, if a VAV reheat coil is already at capacity during certain conditions, increasing the airflow may result in an overcooled zone. Facility staff often have a good sense of existing capacities and potential problem areas, as well.
3. If the equipment can handle the increased load, increase VAV box minimums as well as max airflows for critical spaces, such as break rooms or dining areas. Increase the outside air damper max setting at the air handlers. If the equipment cannot handle the increased load at peak conditions, additional programming can be added to the controls to reset the ventilation back down at maximum heating or cooling.
4. Document everything! When the risk of virus transmission lessens, you will want to bring your facility back to optimum operating conditions. Write down all changes, and track before-and-after utility data to assess the increased operating costs and make sound decisions going forward. Consider retro-commissioning the building at that time to identify any other opportunities for operational improvements, since a lot of parameters have likely changed over time.
Increased ventilation is just one aspect of an overall strategy, which might include improved filtration, UV and/or bipolar ionization, tighter humidity control, etc.
