Modifying the built environment to reduce the spread of COVID-19

There are between 320,000 to 1 million different viruses in the world. Of those, there are 219 known viruses that can infect and cause disease in humans, including coronaviruses. COVID-19 is a type of coronavirus that was identified in Wuhan, China in December 2019. By December 2020, it had infected nearly 20 million people and caused nearly 350,000 deaths in the U.S. alone.

The COVID-19 pandemic is the most severe pandemic since the 1918 Spanish flu. One of the most dangerous characteristics of this virus is how it spreads: through respiratory droplets when an infected person coughs, sneezes or talks. Contaminated particles stay aloft long enough to be subsequently breathed in by another person.

Multilayer infection control mitigation

While social distancing, masks and hand washing are some of the best measures to prevent the spread of COVID-19, the built environment can also support infection control. However, 80 - 90 percent of the buildings that exist in our lifetime are already built, so making small updates to existing buildings is the best path forward.

Building owners can choose from a variety of multilayer infection control modifications to help reduce the spread of viruses within their facilities. The following modifications can be applied to a variety of non-industrial building types where there are high concentrations of people, including office buildings, movie theaters, bowling alleys, restaurants, bars, gas stations, grocery stores and schools.

Humidification to the HVAC system

Preliminary studies show that humans have better immune systems when in higher relative humidity environments, around 40 – 60 percent relative humidity. This results in a reduced spread of COVID-19. The most convenient location to install humidification is the air-handling unit, but depending on how your building’s air-handling unit (AHU) was designed, the humidification may have to be duct-mounted or installed within the occupied space. This is one of the most effective infection control modifications that can be made to reduce the spread of COVID-19.

Higher efficiency filters

Most building HVAC systems have MERV 7 or MERV 8 filters installed, which have 25 - 35 percent dust spot efficiency. While these filter out large particles, they are not efficient at removing smaller particles that contain a pathogen. Adding higher efficiency filters—MERV 13 or MERV 14—to the HVAC system can remove particles infected with COVID-19, as they have about 90 - 95 percent dust spot efficiency. The original MERV 7 or MERV 8 filters need to remain as pre-filters and the MERV 13 or MERV 14 filters should be added downstream of the pre-filter.

Dedicated work station supply air

Providing dedicated supply air nozzles at each work station inside an office building is effective at preventing the spread of COVID-19. Supply air nozzles have small induction areas that pull the air from the ceiling instead of the breathing zone. Any pathogens in the supply air will affect a substantially smaller area.

Upper room ultraviolet lighting

Ultraviolet light (UVC) uses short-wave energy to inactivate viruses, bacteria and fungi so they don’t cause disease. Upper-room UVC light fixtures produce ultra-violet light and are installed below the space ceiling with the UV light pointing towards the ceiling. Most supply air diffusers have high-velocity discharge that creates an induction-air current inside the space and distributes air across the ceiling. The upper-room UVC fixtures inactivate coronaviruses in the supply air stream and are most effective when installed in high-occupancy and transient spaces.

Increased outdoor airflow

Modifying an HVAC system from partial outdoor airflow to full outside airflow will help flush a pathogen out of a building. Caution needs to be taken to increasing outdoor airflow beyond AHU heating and cooling capacity. Verify that a system enthalpy wheel is bypassed on the exhaust side to prevent the re-introduction of pathogens into the HVAC system. This modification will also increase the building’s energy usage. Another option is to put the building HVAC system into economizer mode before occupancy and/or between shift changes.

No-touch operations

From no-touch faucets and automatic doors to voice-activated control systems for elevator banks, no-touch operations are a great way to reduce the spread of viruses in buildings.

Managing cost and disruption to operations

Capital cost and disruption to operations remain the biggest challenges of implementing any of these COVID-19 mitigation options in existing buildings. To keep costs down and your facilities up and running with minimal disruptions, I recommend adopting a multilayer approach. That is, choosing one or two of the above to apply to your building that fit within your budget. Some of the mitigation options above, like adding humidification to your HVAC system, can be done over a weekend, depending on the type of technology you’re using.

Before you implement any of the above COVID-19 mitigation options, evaluate your facility first to ensure that you have the correct infrastructure in place to handle these upgrades.

The return on investment

When weighing which virus mitigation option you want to install in your facility, it’s important to consider the cost of sicknesses in the winter. If you could reduce the amount of sick days that your employees take every fall or winter by 50 percent, how much would you save? That’s what these virus control mitigation options can offer you. They not only help slow down the transmission of COVID-19, but all kinds of viruses, including influenza and the common cold. It all boils down to your return on investment.

Last updated: 1/14/2021