Page 36 - spaces4learning, Spring 2021

spaces4learning K-12 COLUMN
MITIGATING THE RISK OF COVID-19 AND IMPROVING INDOOR AIR QUALITY IN SCHOOLS
Following CDC, ASHRAE Guidelines is Crucial to Healthy Environments.
By Mike Wolf, P.E.
ACCORDING TO THE U.S. Gov- ernment Accountability Office, 40%
of school districts (representing about 36,000 schools nationwide) need to update or replace their Heating, Ven- tilating and Air Conditioning (HVAC) systems. In 2020 and 2021, Congress passed three stimulus bills that provided nearly $190.5 billion to the Elementary and Secondary School Emergency Relief (ESSER) Fund. A significant portion
of the ESSER Fund is earmarked for schools to undertake HVAC system maintenance and make the upgrades necessary to mitigate the spread of COVID-19 and improve Indoor Air Quality (IAQ).
When evaluating options for maintaining and upgrading an HVAC system, it is important to follow guide- lines established by the U.S. Centers for Disease Control and Prevention (CDC). A key CDC recommendation for HVAC systems references guidance from the American Society for Heating, Refrig- erating and Air Conditioning Engineers (ASHRAE). ASHRAE Standard 62.1 outlines the functions that a well-de- signed and maintained HVAC system should perform to maximize IAQ and mitigate pathogen risks. These functions include:
Ventilation
Introducing outdoor air into a building is critical to ensure proper IAQ, as the fresh air allows the HVAC system to purge contaminants (e.g., airborne virus- es, bacteria, volatile organic compounds) from the building. When introducing outdoor air into a building to mitigate the risk of COVID and improve IAQ, consider one or more of the following:
• Disable demand control ventilation to maximize the amount of outdoor air introduced into the space, regardless of occupancy level.
• Run the HVAC system continuously to prevent buildup of contaminants.
• Run the HVAC system longer than normal occupancy mode. Start delivering fresh air into the space before occupants arrive and continue after they leave, providing a pre- and post-occupancy flush of the air.
Filtration
Increasing air filtration is another tool
to mitigate the risk of COVID and improve IAQ. HVAC systems typically utilize filters with a Minimum Efficiency Reporting Value (MERV) rating of 8. MERV 8 filters are effective at capturing large particles, such as dust and pollen, but are not effective at capturing smaller pathogens. Filters with a MERV 13 rat- ing or higher can capture approximately 85% of airborne respiratory particles and are recommended to help capture SARS- CoV-2 and other pathogens.
However, filters with higher MERV ratings will increase resistance to airflow. To overcome the resistance of filters with higher MERV ratings, the ventilation
PHOTO CREDIT ROMAN ZAIETS
system’s fans will likely need to run faster to deliver the proper ventilation rate. Consult a qualified HVAC engineer or contractor to ensure fans have the capacity to run at higher speeds and that the duct system can support the higher pressures.
Circulation
Air circulation refers to how air moves within a space as a function of air rotations and air velocity. Proper air circulation reduces high concentrations of pathogens from forming in a space. Air circulation also aids in destratification (mixing hot air that rises with cooler
air beneath) to help improve occupant comfort and reduce energy costs. High volume low speed (HVLS) ceiling fans are ideal for increasing circulation in a space.
Humidification
Studies show that maintaining a relative humidity of between 40%–60% will reduce the potential of airborne viral transmission. Utilizing energy recovery with a dedicated outdoor air system (DOAS) will help reduce the cost to humidify (or dehumidify) ventilation air. Supplemental humidification and/ or dehumidification can be added to more traditional HVAC systems. Again, it is wise to consult a qualified HVAC engineer or contractor to maximize
your system capabilities and minimize operating costs.
Additive Air Cleaning Technologies
Air cleaning technologies may also be added to existing HVAC systems.
36 SPRING 2021 | spaces4learning.com