At the first sign of illness, most people will head to their primary care doctor or the nearest urgent care for treatment. This means medical office buildings (MOB) are often the first line of defense against infection transmission.

During the COVID-19 pandemic, we took a closer look at the HVAC system and its role in making our locations as safe as possible.

By: Maureen Kozel, PE, and Robert Inman


Prior to COVID-19, HVAC systems at MOBs were very similar to those found in commercial office spaces. The reason for this is simple. Prior to 2015, the International Mechanical Code did not reference the ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) Standard 170-2017 Ventilation for Healthcare. Thus, there are a number of common factors between the building types. As healthcare changed to further promote care outside of hospitals, we saw an influx of health systems and physicians looking to build MOB spaces that met the needs of patients. Now, as we continue to learn and better understand the lasting impacts of COVID-19, we’re finding ways to improve the next generation of medical office buildings.

Here are seven ways that the mechanical system can be improved to help reduce infection risks within the typical MOB.

  1. Additional and more efficient filters. Most MOBs should consider adding a second set of filters with higher efficiency ratings. Filters are measured on the “MERV” scale which stands for Minimum Efficiency Reporting Value. Simply, MERV measures how much matter passes through an air filter. MERV 13 and MERV 14 filters offer three times the filtration rate of typical MERV 7 filters and can capture infectious particulates smaller than 1 micron.
  2. Adjust the relative humidity levels. We recommend adding humidification to maintain a 40%-60% RH (relative humidity). Controlling humidity is no longer just applied to hospitals as studies show this is the optimal range to improve people’s health which increases resistance to infection. Within this range particles tend to settle out of the air faster where they can be cleaned off surfaces.
  3. Stop recirculating air in waiting rooms. This is a practice common in emergency rooms to account for undiagnosed patients who are sitting together. By completely exhausting the air in a waiting room, we’re able to reduce the risk of transmission even after an infected patient has been removed from the waiting area.
  4. Lower air return grills. By placing return/exhaust grilles low on a wall, as opposed to the ceiling, we can avoid re-entraining particulates into the patient’s breathing zone. This follows the isolation room air distribution model.
  5. Cooling needs for technology. To encourage people to stay home, more and more rooms will become dedicated telemedicine areas. This means increased use of technology and a thoughtful approach to ensure reliable cooling for IT and AV equipment.
  6. More fresh air. One of the best things we can do from an HVAC standpoint is to increase the amount of fresh, outside air that is drawn into a building. This will reduce the amount of contaminated air that is recirculated and better flush the building of contaminants. Also, increased levels of outdoor air have shown to positively impact building occupants’ performance and well-being. The volume of outside air directly affects the sizes of heating and cooling coils (first cost) as well as operating costs. Therefore, the percent increase over ASHRAE Standard 170-2017 minimums needs to be evaluated to optimize the benefits versus costs.
  7. Balance energy use with health needs. Some of the measures above will increase energy use as noted in increasing fresh air (Number 6). Energy recovery systems, which use building air that would normally be exhausted to treat the incoming ventilation air, can help recoup some operating costs. However, we need to ensure that this technology will not allow for any cross-contamination between air streams.

HVAC will play a broad role in creating healthier environments across all building types. However, the MOB plays an important role in our healthcare system. It’s important to do what we can to ensure patients and staff feel safe and comfortable reaching out for help when it’s needed.

While MOBs are unique, we put together a building re-entry guide specific to HVAC systems and creating healthy spaces during the COVID-19 pandemic. Check it out here.