HVAC Systems - Fall 2022 Semester PDF
Before the pandemic, most of the air handling units (AHUs) in university facilities were set to operate on schedules that closely matched the occupant density of the buildings. Over many years, these schedules have been developed in consultation with facility managers across campus. They have worked very successfully for years and have greatly reduced the energy usage in campus buildings during times of low occupant density (e.g., nights and weekends).
When the pandemic arrived, professional organizations and government agencies, including the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) and the Centers for Disease Control and Prevention (CDC), published recommended industry guidance on how to operate heating, ventilating, and air conditioning systems (HVAC) systems during the pandemic. Facilities & Services (F&S) implemented many changes to align with these recommendations: physically inspected AHUs to ensure proper operation, verified units have mechanical ventilation wherever possible, installed portable high-efficiency particulate air (HEPA) units in multi-occupant spaces without mechanical ventilation, extended AHU runtimes to flush buildings and enhance indoor air quality, and upgraded to MERV-13 filters wherever possible. Runtimes and ventilation levels were not reduced in buildings due to COVID-19. If a building with heavy laboratory use was already operating 24 hours a day, that schedule was maintained.
The pandemic has taught us that we must continually assess our mitigation measures and recommend adjustments when warranted. F&S engineers have continued to discuss the operation of HVAC systems on campus. Here is a summary of how F&S plans to operate systems following Commencement in May 2022.
HVAC runtimes: The extended AHU runtimes during the pandemic have helped promote good indoor air quality (IAQ), but there is a significant energy cost associated with heating and cooling large amounts of air while our buildings have low occupancy. After careful review, we are now at a point in the pandemic where AHU runtimes can be adjusted to more closely operate based upon building occupant density and current community risk level. The AHU schedules will follow EPA guidance and start prior to scheduled occupancy while keeping Illinois Climate Action Plan (iCAP) goals in mind to balance the benefits of energy conservation and IAQ.
Demand-Controlled Ventilation: Many HVAC systems on campus were initially designed to utilize demand-controlled ventilation with CO2 sensors. Demand control operation ceased during the pandemic to provide increased ventilation in the spaces they serve. The sensors have been calibrated and verified operational in all spaces on campus and have preventative maintenance schedules in place for continued proper operation. HVAC systems with demand-controlled ventilation will be returned to normal, pre-pandemic operation.
Filtration: During the pandemic, F&S upgraded existing AHU filters wherever possible to MERV-13. Staff have confirmed that virtually all central systems were able to handle this change with minimal energy impact. F&S has updated the Facilities Standards to make MERV-13 our new, permanent minimum standard for final filters (up from MERV-11 previously).
Portable HEPA Filter Units: F&S previously identified some spaces on campus that lacked mechanical ventilation. At first, opening windows or using portable HEPA filtration units was recommended to help with indoor air quality in those areas. Today most spaces of this type migrated to using portable HEPA units instead of utilizing operable windows. F&S will continue operating and maintaining these units to promote indoor air quality in poorly ventilated areas.
Operation of university HVAC systems in this manner will allow us to promote the health and safety of students, faculty, and staff while also optimizing campus energy usage. It is also in alignment with the university’s Indoor Air Quality Action Plan, which was developed in response to the EPA’s Clean Air in Buildings Challenge. F&S will make these adjustments as soon as practical following Commencement. This process will take a couple weeks to implement, and the changes will be fully in place prior to the Fall 2022 semester.