Retro-Commissioning for the Pandemic
Confirming that an HVAC system is functioning as originally intended is the least a building owner/operator can do for any occupied building during the COVID-19 pandemic. This means confirming that supply and exhaust fan belts are secure, fan motors are operational, outside air dampers stroke fully from open to closed upon a signal from the control system, the control system is programmed to maintain an appropriate minimum outside airflow, and that temperature and ventilation sensors are calibrated and communicating with their controllers.
Many owners are considering modifications to their HVAC systems in hopes of reducing the risk of virus transmission within their buildings. These strategies include increased outside air ventilation, continuous (24/7) air system operation, increased filter efficiencies, ultraviolet disinfection, improved relative humidity control, relative space pressurization, and directional/laminar airflow.
In addition, many HVAC equipment manufacturers are introducing products focused on mitigating COVID-19 transmission. It is overwhelming for most building owners to know what to believe and what to try.
One overarching recommendation I’m comfortable making is to carefully evaluate every strategy against its appropriateness for each unique building and HVAC system. Refer to ASHRAE and the Centers for Disease Control and Prevention (CDC) for their latest guidelines and research results (or lack thereof) associated with each of the strategies under consideration. Engage a professional engineer to study the potential impact of each strategy on the existing HVAC system, keeping in mind that systems consist of multiple components, and making changes to one component may impact the performance of others.
Of course, whatever modifications you make, they should be commissioned. It is critical that the current facility requirements (CFR) be documented at the start of any COVID-19 project to record the intentions of each strategy. The commissioning process can then be used to confirm those goals have been achieved.
Are new strategies performing as intended at the end of the project? Is the balance of the HVAC system performing as intended? Are building operators trained on the maintenance, operation, set points, and intent of a system’s modifications? Will there be ongoing monitoring and verification to ensure COVID-19 strategies remain effective over time?
Finally, each strategy should be characterized as permanent, i.e., intended to remain in place after the pandemic, or temporary, i.e., only for the duration of the pandemic. Because many COVID-19 strategies are energy-intensive, building owners and operators need to remember to revisit the CFR and make adjustments when the pandemic is finally behind us.
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