With the 2019-2020 school year cut dramatically short by the CO- VID-19 pandemic, public and private school systems and higher education institutions across the nation are exploring strategies today to prepare their buildings for a safe return to school this fall. Appropri- ately operating and maintained HVAC systems will play a critical role in creating a safe environment—and in building trust from staff and parents as these buildings are reoccupied. As the Philadelphia Federation of Teachers recently learned from a 13,000-member survey, teachers are adamant that they will not return to school until facilities are in adequate condition. Schools that do not have a plan in place for a safe reopening will be hard-pressed to bring faculty and students back to the classroom. This plan should also address occupant perceptions of an unsafe building that may become conflated with COVID-19. While there are abundant recommendations for reopening schools, it will be important that each school address their specific mechanical needs based on available resources, school demographics and specific building characteristics to create an effective approach to achieve their safe reopening and re-occupancy. Further, schools should periodically reassess their plans as communities move into different phases of re- opening and deeper knowledge of response to COVID-19 becomes available. A varied response Across the board, schools are being advised to create layered control strategies, focusing on de-densifying classrooms, increasing physical spacing, improving ventilation, upgrading filtration, and considering supplemental air cleaning. Increased ventilation of spaces using clean air has proven to be an important and effective tool in helping prevent the spread of COVID-19 as it dilutes the concentrations of the virus in the air. Although Centers for Disease Control and Prevention (CDC) recommendations focus largely on disinfection and social distancing protocols, it offers brief guidance on school mechanical systems: “Ensure ventilation systems operate properly and increase circula- tion of outdoor air as much as possible, for example by opening windows and doors. Do not open windows and doors if doing so poses a safety or health risk (e.g., risk of falling, triggering asthma symptoms) to children using the facility.” The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) provides more robust guidance to help schools Preparing Schools for a Safe Reopening: Recommendations for HVAC Maintenance and Support By Brian Baker, P.E. and John McCarthy, Sc.D., C.I.H.
identify specific opportunities for increasing ventilation. However, it’s important to note this guidance is being updated on an ongoing basis on the ASHRAE website, www.ashrae.org, as research around SARS- CoV-2 evolves. The challenge, of course, with this broad advice is that there are a wide variety of natural, mechanical (both local and central) and hybrid mechanical systems operating in schools across the country. More- over, many older schools, particularly public K-8th grade facilities, may be challenged in achieving adequate air distribution in the class- rooms due to the age and limitations of their HVAC systems. Many of these systems may struggle to meet pre-COVID code requirements or ASHRAE recommended ventilation rates, as highlighted in a June 2020 Government Accountability Office report. This report concluded that more than 40 percent of the nation’s school districts need to update or replace systems, including HVAC and plumbing, in at least half of their schools. That amounts to approximately 36,000 schools begin- ning their COVID-19 response plan at a disadvantage. However, this report also offers a starting place. Schools must begin by examining their own ventilation systems for maintenance needs and opportunities to increase ventilation. HVAC and other routine mainte- nance will become absolutely critical in creating a safe environment. Must-do maintenance for HVAC equipment Today, school facility managers have an incredibly strong and very valid case for growing their maintenance budget, so this is no time to hold back on inspections and identifying needed corrections or delay- ing preventive maintenance. The first step is to begin with a review of existing systems to ensure they're performing as intended. That includes examining air handling systems to make sure dampers are connected, fan belts are in good condition and appropriately tensioned, cooling and heating coils are functional and working appropriately, filters are being maintained, etc. This also includes ensuring general cleanliness of units, condensate drain pans, and related components. Further, knowing the actual flow- rates for both outdoor air and recirculated air for each space that is intended for reoccupancy is essential in helping decide upon allowable class sizes. Now is also the time to review common historic complaints about indoor air quality to identify patterns or problem areas. Any existing maintenance concerns must be addressed because they can give the impression of poor indoor air quality and erode faculty and parent trust in the building’s safety. Today’s maintenance activities should also include putting a plan in place for managing both routine preventive maintenance as well as the actions that may be needed to address potential system trade-offs that may be associated with increasing ventilation rates. The most signifi- cant of these is likely be to thermal comfort. By increasing outdoor air ventilation beyond design limitations, you risk sacrificing comfortable temperature and indoor humidity levels. More than uncomfortable, this could heighten occupant concerns about the overall health and safety of the building.
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august 2020
csengineermag.com
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