All Systems Go: Building Readiness in Response to COVID-19
COVID-19 has created a significant uptick in the interest of building systems, and the impact on operating costs, air quality, and wellness, particularly as economies and communities re-open. In this article we look at considerations related to building systems to provide a starting place as you prepare and launch new protocols for operations. This is just one element of a more comprehensive approach that encompasses facets of policy, building design, and healthcare delivery models.
Heating, Ventilation, and Air-Conditioning Systems
Modern HVAC systems allow for temperature and humidity control, introduction of ventilation air, and filtration. Consider making an upgrade if you have an older, less-than-capable HVAC system.
Research shows that a relative humidity range of 40-to-60% RH, compared to drier conditions, supports respiratory immune system efficiency, reduces virus “float” time, and virus survival time. An RH below 40% increases travel distance for viruses due to its impact on droplet size and impacts the actual stability of the virus while an RH above 60% can create conditions for mold to grow. While most HVAC systems can dehumidify to 60% RH, most also do not have active humidification. During the winter, in cold climates, where indoor RH may drop significantly below 40% a system with active humidification should be considered.
Modern ventilation standards, such as ASHRAE 62.1, address the delivery of oxygen to replace carbon dioxide to offset odors from finishes and occupants, and to dilute other contaminants. With COVID-19, there is now increased interest in additional ventilation which serves to dilute viral concentrations.
Modern HVAC systems incorporate multiple stages of filtration, known as a pre-filter and final filter. Filtration effectiveness is categorized by MERV ratings, with MERV 8 for pre-filtration and MERV 13 for final filtration being most common. The higher the value, the more efficient the filter is at removing particles. Higher levels of filtration come with potential energy and cost considerations. Alternative air treatment technologies, such as UVGI or bi-polar ionization, have received significant attention, but should be considered with care in all applications.
The proper design of air delivery requires an integrated design approach. Two types of distribution commonly used are mixed air and displacement. Mixed-air diffusers are designed to mix room air with treated air from an air-handling unit or fan coil unit rapidly. There is currently some concern that air can promote transfer of virus from person to person within the direction of air movement. This transmission pathway is currently being studied by research organizations. Displacement systems use another approach to air distribution which supplies cool air at low speed from floor level, allowing heat from occupants to naturally drive air upwards, where it is captured at ceiling level. This approach is also being studied specific to the transmission of SARS-CoV-2.
As many facilities have had to stop operations, facility owners have communicated their curiosity and interest about energy usage and reduction. If spaces have no occupancy, systems can be run at significantly reduced demand, including the use of elevated temperature setpoints and reduced ventilation. It is important that a facility operations team is aware of these adjustments, as air quality may be compromised in this type of operating mode.
As potable water systems see low or no demand, stagnant water has raised concern over bacterial growth, including the increased potential for Legionnaires Disease. Adequate flushing of potable water systems is particularly important.
For deeper data rich insights on building operations, consider a monitoring-based commissioning approach to building operations and utilizing automated fault detection and diagnostics. An indoor air quality certification program such as RESET prioritizes on-going results and long-term occupant health. It requires data to be live streamed to the cloud via multi-parameter monitors that can be accessed from any digital device.
As you build your plan to safely re-open facilities, use our downloadable building readiness checklist to start the process.
We recommend reviewing the resources below directly for the latest commentary on solutions to some of the considerations we’ve raised. Before any measures are implemented, consider both the short-term and long-term impact. Keep in mind that although no single measure can reduce transmission risk to zero, they can have positive results for energy usage as well as overall health and wellness.
- ASHRAE Position Document on Infectious Aerosols
- ASHRAE Environmental Health Brief, COVID-19 and Airborne Transmission
- World Health Organization COVID-19 Resource Site
- CDC COVID-19 Resource Site
- Harvard Business Review, What Makes an Office Building Healthy
This article was authored in collaboration with Lloyd Ramsey.