By Sonya M. Pouncy, CEM, CMVP, LEED-AP. Sonya is a senior engineering consultant with Energy Sciences. The firm helps clients meet energy challenges with practical solutions that reduce waste and increase net operating income.

COVID-19. This is an “all-hands-on-deck” moment and I find myself wondering what I can do to help. Yes, I am practicing social distancing. Yes, I’m washing my hands often and monitoring my temperature. I’ve even pulled my neti-pot out from the back of the linen closet. Still, I’m not a doctor, first responder, or sanitation worker. Not a truck or delivery driver. What can a consultant in building energy management offer at a time like this? Well…

In the U.S., we spend about 80% of our time inside buildings. In response to the corona virus, we may spend more than that as many of us hunker down at home. Arguably, the building system having the greatest influence on human health is the HVAC system. Not only does it determine temperature, it largely controls air quality, too. Right now, a lot of our commercial buildings are empty, but eventually we will return to them. When we do, how might we operate and maintain their HVAC systems to provide good indoor air quality and help reduce the risk of disease transmission?

Adapted from: ASHRAE. 2016. HVAC Systems and Equipment.

Here are my top three suggestions:

  1. Check that control setpoints are where they should be. Especially for space humidity. We tend to have more respiratory complaints during the winter, and this is often linked to low relative humidity. Epidemiological studies have found that, buildings that maintain relative humidity between 30 and 60% have lower rates of reported respiratory illness.1 The good news is that the optimal range of relative humidity for humans is not so good for bacteria and viruses. In a 2010 study2, researchers found that in warm, dry indoor environments (around 68°F, 20% RH) approximately 80% of corona virus samples3 deposited on surfaces remained infective and virulent for about one week. But, when relative humidity was raised to 50%, the number of viable corona viruses dropped to about 1% in roughly 2 days. Other microorganisms, like the influenza virus and the Pneumococcusbacterium, also lose much of their virulence at 50% RH.4
  2. Maximize the use of fresh, outdoor ventilation air. Remember the old adage: “dilution is the solution to pollution.” Bringing plenty of fresh air into the building can help reduce concentrations of air-borne pollutants, including viruses. Check that dampers are in good working order. If the HVAC system has an air-side economizer, use it. If the system uses demand-controlled ventilation, consider modifying the setpoints for the time-being so that ventilation rates remain high even as building occupancy falls. If you do this, however, you’ll want to be sure to pre-determine a time to revisit the setpoint adjustment. Eventually, you’ll want to re-establish the tracking between ventilation rates and occupancy.
  3. Start spring cleaning early and begin with the air distribution system. Change the filters in air handling units (AHUs), packaged roof top units and terminal units like unit ventilators and packaged terminal air conditioners. Inspect diffusers, grills, and registers for dirt accumulation and clean them as necessary.  Clean components such as heating & cooling coils, fan blades, drain pans, dampers, condensate pumps, and panel walls. And, be sure to check the fit of the filters in their housing and the seal integrity. Replace any worn or damaged equipment.

These are just a few of things we can do to help ensure that our buildings provide us with healthy indoor environments in which to live, work, learn, and play. For additional O&M best practices for your HVAC system and ways to reduce the risk of transmission of infectious diseases, consider these ASHRAE resources.

  • Position Document on Airborne Infectious Diseases
  • Standard 55: Thermal Environmental Conditions for Human Occupancy
  • Standard 62.1: Ventilation for Acceptable Indoor Air Quality
  • Standard 62.2: Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings
  • Standard 170: Ventilation for Healthcare Facilities
  • Standard 180: Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems
  • Guideline 0.2: Commissioning Process for Existing Buildings and Assemblies
  • Guideline 29: Guideline for the Risk Management of Public Health and Safety in Buildings
  • Guideline 32: Sustainable High-Performance Operations and Maintenance

This, too, shall pass. In the meantime, may you and your families stay healthy as we all practice the most essential of human characteristics—the abilities to adapt and find peace.


  • ASHRAE. 2016. Humidifiers. HVAC Systems and Equipment. pp. 22.1-22.16
  • Casanova, Lisa M., et. al. 2010. Effects of Air Temperature and Relative Humidity on Corona Virus Survival on Surfaces. Applied and Environmental Microbiology. 76(9), 2712-2717.
  • Samples used in the study were proxies for SARS-CoV, the corona virus that causes SARS. While this is not the same virus that causes COVID-19, it is in the same family of viruses and similar results can be expected.
  • ASHRAE. 2016.


Disclaimer: Information on COVID-19 is emerging and rapidly evolving. The suggestions in this blog should be considered along with the specific characteristics and requirements of your building as well as the building owner and occupant criteria.

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