Are you restarting your business or increasing capacity as COVID-19 restrictions change? Perhaps you’re reopening an office building, bringing more students into your school, hosting in-person events, or increasing capacity in your store or restaurant. You’re likely putting a lot of thought into ways to bring more customers, visitors, and staff into your building while making sure they feel safe and remain healthy. This is especially important inside, since we know COVID-19 is spread through airborne transmission indoors.

One key strategy to reduce virus transmission is maintaining good indoor air quality (IAQ). But simply running the HVAC system more isn’t the whole answer, and it’s costly. Consider taking the actions we describe below to improve air quality and keep your systems running efficiently.

Some measures could increase your expenses at a time when many businesses are struggling financially. Look for support programs like Commercial Property Assessed Clean Energy (CPACE) funding or efficiency incentives from your utility to help reduce costs. You can learn more about CPACE on the Better Buildings Financing Navigator.

Maintaining good IAQ will remain important even beyond the COVID-19 pandemic. Your building will benefit from improved air quality, and you’ll be well prepared for future outbreaks.

HVAC systems and public health

You can make your building more resistant to respiratory virus transmission and increase the safety of your employees, customers, students, or patients by adjusting your HVAC. You can even share how you’ve modified the HVAC system to show them you care about their health and to help them feel more comfortable in your building. With the wrong information or poor planning, some building managers alter their HVAC practices in ways that don’t decrease COVID-risk and unnecessarily increase energy consumption. The solutions below help to keep your building safe without wasting energy.

Install low-pressure-drop MERV 13 filters

To keep your air fresh and clean, you can bring more outside air into the building or upgrade your filters to remove more virus particles from the recirculated air. Installing new filters is often the better option because it’s usually cheaper than conditioning a lot of outside air. Retrofit the HVAC systems with Minimum Efficiency Reporting Value (MERV) 13 filters, which reduce virus transmission. Hire an engineer, contractor, or commissioning agent to design the retrofit and make sure the filters are properly installed, the edges are sealed, and the HVAC system performs as expected.

Use natural ventilation

When outdoor air temperatures are close to your preferred indoor temperatures, open windows or doors to increase ventilation. More fresh air will enter your building but the ventilation system won’t spend much more energy. If you tend to open doors and windows frequently, consider adjusting your temperature setpoints to account for it: set them warmer in the summer and cooler in the winter.

Add or use economizers for air-conditioning

Economizers reduce the need for mechanically cooled air by drawing cooler outside air into the building through a controlled vent on the rooftop unit. Economizers can increase ventilation rates and reduce HVAC energy consumption under the right conditions. Use economizers whenever possible and make sure they’re working properly.

Adjust, rather than disable, demand-controlled ventilation

Demand-controlled ventilation (DCV) adjusts how much ventilation is used in response to how many people are in the building. During the pandemic some organizations, like ASHRAE, recommended disabling the system to be sure air circulation remained high at all times. But the Western Cooling Efficiency Center (WCEC) instead recommends adjusting the carbon dioxide (CO2) setpoint—to less than 1,000 parts per million, for example—and monitoring levels continuously. With this strategy, you won’t lose all the energy savings of DCV.

Tune up the air-conditioning system

HVAC systems might be working overtime, especially if your DCV systems aren’t running or you’ve adjusted them to keep ventilation rates high. Don’t let the HVAC system waste energy through neglected maintenance. Tune up your HVAC system with the following steps (follow this list in order if you need to complete all tasks):

  • Inspect and repair the economizers or dampers
  • Recommission the variable-frequency drive controls
  • Replace and upgrade filters
  • Check and adjust airflow
  • Reevaluate thermostat temperature setpoints and consider increasing them in the summer or decreasing them in the winter (particularly in low-occupancy areas)

Use energy management and information systems

Energy management and information systems (EMISs) understand and control the energy-consuming systems in your building, allowing for better control and more energy savings. They can make it easy to operate your HVAC system and keep it running efficiently. For example, as part of an EMIS, some networked smart thermostats let you quickly increase ventilation rates across your HVAC systems without having to do any manual work yourself, such as walking to every thermostat in your facility. Some EMIS options now include an epidemic mode that decreases illness transmission without unnecessary increases in HVAC energy consumption.

Perform commissioning on your building’s systems

Consider commissioning or recommissioning the building to be sure all systems are calibrated correctly. This process helps your building operate safely and efficiently. When the risk of COVID-19 transmission is high, commission the ventilation system under the assumption of full building occupancy even if fewer people are present as part of social-distancing practices. The amount of ventilation per person still increases but the equipment isn’t overworked. Look into monitoring-based commissioning if you want to have an ongoing view of your building’s energy systems.

Add energy recovery ventilation

Energy recovery ventilation (ERV) can reduce the energy consumption of large facilities that have high ventilation demands. ERV captures thermal energy and moisture from the air leaving the HVAC system and transfers it to air entering the system, saving energy and possibly improving humidity control. Heat recovery ventilation (HRV) only transfers heat, not humidity, from the exhaust airstream to the intake airstream. HRV is typically less expensive, but ERV is better suited for humid environments because it reduces the need for dehumidification. HRV systems can have efficiencies as high as 95%, and they often have payback periods of 3.5 years. Consider either of these units, especially if your building’s in a very cold or very hot and humid climate.

Monitor indoor air quality

Monitoring IAQ might provide information about the safety of your building and how much ventilation is needed to minimize the possible spread of COVID-19 indoors. Although there isn’t a clear consensus on the issue, a report in Environmental Science & Technology Letters, Exhaled CO2 as a COVID-19 Infection Risk Proxy for Different Indoor Environments and Activities, found that CO2 levels indoors trend with COVID-19 risk. This suggests that checking CO2 levels might be a useful way to monitor IAQ.

Use ultraviolet technology to sanitize air in ducts

Ultraviolet germicidal irradiation (UVGI) has been shown to be effective for disinfecting flowing air, but its effectiveness depends on the type of pathogen, air velocity, humidity, size of particles, and the design of the UV system. Some research has shown that a form of UV light, UV-C, is effective in deactivating the virus that causes COVID-19. You can install UVGI in ductwork to sanitize the airstream, though research suggests it’s probably only necessary for high-risk scenarios. If you’re already getting good filtration or ventilation, installing UVGI might not be worth the added cost or complexity. There are two ways to install UV lamps in ductwork:

  • In-flight. The airstream passes through UV lamps, deactivating airborne contaminants.
  • In-duct coil treatment. UV light is directed at cooling coils and drain pans of the HVAC systems to reduce bacterial growth and prevent a microbial film from accumulating on the coils.

Only the in-flight application has potential safety benefits for COVID-19. But in-duct UVGI systems may provide energy-efficiency benefits and increase the lifetime of your HVAC equipment by keeping the coils clean.

Steps to restart your building

Many commercial buildings had to be shut down hastily, and building managers weren’t used to planning for long-term vacancies. As you reopen your building, work backward from how you shut down the equipment to be sure you restart all systems safely, without damaging the building or its equipment. In particular, you should check or adjust building controls and HVAC and refrigeration settings. Use the building-restart checklist to be sure your systems run efficiently (figure 1).

Figure 1: A building-restart checklist

The building-restart checklist guides you through your main energy systems and top uses—electricity, gas, water, lighting, and HVAC. Use it to check the condition and maintenance needs of equipment throughout your building.

More resources on air quality, buildings, and COVID-19

The World Health Organization’s Roadmap to improve and ensure good indoor ventilation in the context of COVID-19 and a Taylor Engineering COVID-19 White Paper provide guidance on maintaining good IAQ throughout the pandemic.

The WCEC website Improving Indoor Air Quality in California Schools offers resources on reopening buildings and the science behind IAQ.

The ASHRAE report Guidance for Building Operations During the COVID-19 Pandemic (PDF) asserts that HVAC systems in nonmedical buildings typically play a relatively small role in the transmission of infectious diseases. For more guidance from ASHRAE, refer to its Coronavirus (COVID-19) Response Resources from ASHRAE and Others.

The Better Buildings Initiative webinar Navigating Air Purification Technologies During COVID includes information on air quality and a presentation (beginning at minute 33 of the recording) that focuses on how you can decide which technologies are best for you.

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