Building Operations During Extended Low Occupancy

With states extending the duration of their stay-at-home orders from weeks to months (now into June in some locations), many property teams are adjusting building operations to reflect an extended period of low to no occupancy.  From a health and life safety perspective, the two main considerations are air and water, but property teams are also changing work schedules to guard against an outbreak among staff.


While some buildings are opting to reduce HVAC operations in order to save on operating costs during the shutdown, most engineers are running their air handling systems at or near normal. This helps protect the health of janitorial crews still working as well as the handful of tenants and building staff that remain.

For buildings that must continue normal operations due to tenants doing essential work, maximizing outside air (up to 100 percent, if outside temperatures allow) and filtration are prudent steps.  Installing MERV- 13 filters (or the highest rating allowed in your system) will help prevent airborne transmission of aerosolized virus particles. If changing filters, experts recommend doing it early in the shutdown, as filters become more effective over time as they collect airborne contaminants. Seal the edges of the new filters to minimize bypass.  And treat the old filters as if contaminated – wear personal protection and seal the old filters in plastic before disposal.

If tenants request reduced HVAC during the shutdown, engineers recommend still running equipment for a few hours a day several days a week to maintain air quality and prevent any number of mechanical problems that can occur from laying idle too long.


One significant risk posed by extended closures or low occupancy is bacterial contamination of water in pipes, water heaters, dishwashers, and refrigerators. Biofilm can develop in stagnant potable water in just three to four days, according to Ray Petrisek, a senior microbiologist at HP Environmental, Inc., an environmental consulting firm specializing in building science and toxicology. (Petrisek spoke at a recent BOMA International webinar).Once established, biofilm poses a serious problem that is expensive to remediate. Running water also prevents traps from drying out, which can lead to more contamination (dry traps were a source of viral spread during the 2003 SARS outbreak.)

To prevent contamination, Petrisek recommends running all water supply outlets every two to three days – every faucet, toilet, kitchen sink, dishwasher, etc.  While janitorial crews may flush water in common areas every night or two, they may not be doing this inside tenant spaces. Property teams may want to make arrangements with tenants for someone to run the water sources inside their space during the absence. Upon re-occupancy, tenants should change out ice in ice makers several times.


As the shutdown drags on, many buildings have divided their staff into two teams that rotate week on, week off.  Should an infection spread among one team, the other should be able to step in (after a thorough cleaning). This may be impossible for smaller properties with limited staff, but it’s an excellent time to cross-train engineers and maintenance techs on other buildings in a portfolio.

Security and Other Considerations

Low-occupancy buildings can create security risks, as fewer eyes are present to spot potential trouble. If unable to switch to after-hours (badge only) access, buildings may look at increasing security presence or patrols during the shutdown.

Many property managers and chief engineers caution against reducing staffing during the slowdown for two reasons – losing experienced people and hampering the ability to return to normal operations quickly once the stay-at-home orders lift. But in areas where the shutdown spills into several months, one area in which to reduce operating costs is the frequency of trash and recycling pickup.

Finally, property teams in low occupancy buildings say this can be a good time to catch up on long-delayed projects, complete annual (online) trainings, and tend to all the tasks that typically sit on the back burner.