If you own or operate any type of facility, in the last six months you read articles, attended webinars, and maybe even used Google to search “HVAC ventilation COVID.” Although you learned about the effectiveness of humidifiers, ultraviolet lights, and bipolar ionization, your operating budgets have tightened up and it is hard to know if these technologies will be right for you in the long run.
You likely reverted to simple HVAC changes such as extending ventilation schedules; reviewing your HVAC control systems; inspecting outdoor air intakes and air filters; upgrading to MERV-13 filters; and manually increasing outdoor air damper positions. These are all examples of measures that have helped keep businesses going.
Now may be the right time to further improve the way you go about increasing ventilation rates. Ideally, we can move away from arbitrary increases in ventilation and really start to make better changes. The following recommendations could be your next steps to improve how you add more outdoor air (OA).
ASHRAE 62.1 Ventilation
ASHRAE 62.1 Standard for Ventilation and Indoor Air Quality has set the standard for ventilation for a while now. While building operators have attempted to increase ventilation rates to mitigate COVID risk, unless both actual and target airflow rates are known, the increases will be somewhat of a guess. Using ASHRAE 62.1 can eliminate the guesswork.
Determining ASHRAE 62.1 airflow rates does require some leg work to correctly input all parameters into your calculations, and prior knowledge of your building and the Standard is helpful. The payoff is that once the calculations are done, you then have a standard against which you can weigh actual OA rates.
After establishing minimum OA quantities, you should adjust system-level flow rates to match. If you have OA flow stations that actively read airflow, these should be calibrated. If damper positions are the only indicator of OA quantity, actual flow measurements should be correlated to damper positions. Both ways allow actual OA to be compared to target rates. To take it a step farther, you can balance airflows at the zone/space level. This will help ensure the system’s ventilation is correct and each space is properly ventilated.
Once base airflows have been established, it is easy to accurately increase ventilation airflow.
Enhanced Indoor Air Quality Mode
Many facility managers have manual control overrides to bring in more outdoor air. This can be simple and is sometimes effective. Yet it is worth considering if ventilation changes can be done in a way that also minimizes energy consumption while still being easy for the operator to enact. What if a simple push of a button in your control system automatically enabled an “emergency” or “enhanced” indoor air quality (IAQ) mode that increased outdoor air when the systems can handle it and when it is most cost-effective to do so? Incorporating this idea takes a little more understanding of your systems and more control programming, but it can have a substantial benefit both now and in the future.
For implementation, you will need to customize control sequences to fit your system. But it does not need to be overly complicated. Demand-control ventilation can be automatically disabled; economizer enabling can be extended outside of normal temperature or enthalpy ranges; and the limits of increasing outdoor air can be set by factoring in loading on heating or cooling systems. This will help ensure you have system capacity and also help keep energy costs manageable.
The good thing about perfecting your OA flow rates and creating automatic controls for enhanced IAQ is these measures will serve you well beyond any immediate COVID needs you face. Reestablishing ASHRAE 62.1 ventilation rates is a good practice often included in retro-commissioning, and having an easy way to increase ventilation at the push of a button while simultaneously minimizing energy consumption will be a benefit in emergencies.
While there is no one-size-fits-all approach for HVAC, most facilities can customize these universal strategies to be effective regardless of system type, changes you may have already made to ventilation controls, or what the future of your facility looks like regarding occupancy levels and space usage.