Health authorities have provided guidelines to prevent coronavirus infections in buildings, and governments have placed restrictions that vary by location. Many businesses have been forced to close fully or partially, and collaborators are being instructed to work from home. This means that many buildings are staying unoccupied for long periods.
An empty building can run with less systems and less energy, but shutting everything down can have serious consequences. For example, uncontrolled humidity will likely cause a major mold infestation, and the dangerous Legionella bacteria thrives in stagnant water. Also, data centers with mission-critical applications must stay operational, and they need electricity and air conditioning. Before shutting down a building, facility managers must identify all the systems that must stay operational, and configure them properly.
Keep suitable indoor conditions in your buiding during the COVID-19 lockdown.
Managing an unoccupied building is much easier when a Building Automation System (BAS) or Building Management System (BMS) is available.
- Indoor conditions can be monitored remotely, and equipment setpoints can be adjusted without visiting the building.
- Keep in mind that not all BAS have remote access by default, so make sure this feature is available.
- You can “save” the BAS configuration for normal operation, and then make adjustments for the unoccupied state. When the building reopens, you can establish the normal configuration instantly.
Effective communication is also important, especially with your maintenance personnel, since they may be required to visit the empty building for routine checks. Technical documents like building plans, operation manuals and maintenance reports should be available digitally, to simplify maintenance tasks.
Keeping Suitable Indoor Conditions in Unoccupied Buildings
ASHRAE does not recommend shutting down the HVAC system when a building is empty for long periods. Uncontrolled temperature and humidity can quickly degrade indoor conditions, and building owners will face expensive repairs if this is allowed to happen.
Since there are no occupants, heating setpoints can be lowered while cooling setpoints are increased. The ASHRAE recommendation is a heating setpoint of 65°F and a cooling setpoint of 80°F. These temperatures would be uncomfortable for many occupants, but they conserve a stable environment in empty buildings. Relative humidity should be kept between 40% and 60%, since this range minimizes the survival rate of viruses and bacteria. Keeping RH below 60% is also an effective way to kill mold and its spores.
Buildings with multiple boilers should use as few units as possible when they are unoccupied. Dry storage with a dessicant or inert gas is recommended for boilers that will be off. When these boilers are restarted, they should follow the same procedure as a new boiler.
Chillers, cooling towers and all hydronic piping must keep regular circulation to avoid water stagnation, which causes corrosion and Legionella growth. Any hydronic system that will be inactive for an extended period should be drained completely. Unchecked corrosion can cause major damage to hydronic systems, leading to costly repairs. Regular biological testing is also recommended to keep microbes under control.
Plumbing systems are also susceptible to biofouling and corrosion. Plumbing fixtures should be flushed or turned on at least once per week to prevent water stagnation, and their P-traps and U-traps should be kept wet. ASHRAE recommends circulating all hot water systems at 140°F, at least every two weeks and for a two-hour period.
Managing Electrical Systems During a Building Pause
Electrical installations should only be disconnected if they are not used by any of the systems that stay operational. This reduces the risk of electrical faults when the building is empty, and some energy is saved by disconnecting standby loads. Contrary to popular belief, the standby consumption of plugged devices is very small, but it can add up in large commercial buildings.
Building owners must make sure that the power source stays available for mission-critical data centers, and their associated HVAC systems. Any computer equipment that must be accessed for remote work must also stay powered and connected to the Internet.
The electricity supply is also critical for fire protection systems, since the risk of fire is always present. Since there will be nobody to spot a fire if it occurs, the building relies completely on automatic fire protection. Emergency power systems must also be monitored and tested, according to local codes and manufacturer specifications.