Healthy Schools: It’s in the Air

by Marcy Marro | November 1, 2021 12:00 am

Strategies for designing new facilities with healthy indoor environments are abundant, but what about existing buildings? Established standards and conventions for ventilation rates and filter efficiency are not necessarily adequate to protect occupant health and promote wellness. Additionally, deferred maintenance, system overrides and other issues common in existing buildings prevent them from meeting the minimum IAQ standards.

Nowhere is this more evident than in public schools, which have long suffered from inadequate facilities funding which significantly impacts learning environments. We must address the environments that so dramatically impact children’s health, wellness and cognitive function. School districts faced a gargantuan challenge in preparing for the return to in-person instruction.

While remote schooling was necessary at the height of the pandemic, it is not sustainable. Distance learning was challenging for many students, teachers, and parents and caused some students to slip behind. With the Delta variant surging in the late summer, low vaccination rates in many regions, and children under 12 still ineligible for vaccines, the risks of bringing students and teachers back into schools were significant.

The Seattle Public School District took a proactive approach to ensure health and safety in their schools, which offers important lessons for other institutions. SPS engaged Engineering Economics Inc.[1] (EEI), a consulting firm specializing in building systems performance improvements, to guide a safe return to in-person learning. This program started last spring when the District transitioned to a hybrid model with limited classroom instruction. EEI guided the systematic evaluation of ventilation systems in approximately 100 schools, ensuring that all systems provided effective ventilation, and, where possible, maximized outside air ventilation rates to reduce COVID-19 risk via dilution ventilation. Many HVAC units were converted to 100% outside air, which was practical going into summer when the limited increased energy impact was a small price to pay to ensure student and staff health and safety.

Over the summer, the District’s effort shifted to preparing for full-time, in-person instruction when the fall semester commenced. Based on Centers for Disease Control and Prevention[2] (CDC) and Washington State Department of Health (DOH) guidelines, this comprehensive program applied a layered approach to create a safe and healthy environment for teachers and students. The program worked within the limits of the District’s budget and existing building systems, some of which are over a century old. It incorporated typical policies and protocols, including personal protective equipment use and administrative controls such as scheduling, physical distancing, and evidence-based cleaning routines. Notably, it also included a robust approach to engineering controls.

Operating the HVAC at 100% outside air was a reasonable solution in the spring, but wasn’t sustainable over the winter. Keeping students in the schools required a new approach. EEI developed a reliable process to determine COVID-19 risk exposure. They recommended a mix of effective and cost-efficient engineering controls for classrooms, cafeterias and other key spaces. To achieve the DOH target of six effective air changes per hour (ACH_e), EEI’s analysis factored in occupant density, occupancy duration, air filtration levels and ventilation rates for each space. When the ACH_e fell short of the target, EEI recommended the appropriate number of HEPA air cleaners to close the gap.

The strategies to meet the ACH_e target depended on the existing HVAC systems. Some schools with modern systems allowed easier enhancements (MERV 13 filters and increased outside air), making an effective 6 ACH achievable with a few air cleaners picking up shortfalls. The systems in older schools cannot always accommodate the same improvements. In these cases, more air cleaners were needed to meet the ACH_e target.

Initially, cafeterias were assumed to be higher-risk spaces because the entire school population cycles through them, space constraints limit physical distancing, and students can’t wear masks while eating and drinking. Surprisingly, modeling revealed lower risk in cafeterias than in classrooms due to shorter occupancy periods and larger air volume. Exposure duration and intensity influence our “exposure response” to SARS-CoV-2.

To validate the efficacy of the engineering controls and provide assurance to stakeholders that schools are safe, EEI engaged Intertek’s team of building scientists and industrial hygienists to perform IAQ testing. The team divided the testing process into two phases: unoccupied and occupied.

Phase I focused on sampling particulate matter (PM) in classrooms and other spaces before the start of the school year. Concentrations of PM_2.5 and PM₁₀ were the most relevant parameters to measure the effectiveness of ventilation, filtration and air cleaning strategies in unoccupied spaces. The assessment demonstrated that most of the schools were ready for the safe return of students. It also identified some spaces that required corrective action and highlighted maintenance and operation issues that needed attention.

The team conducted Phase II during school hours in occupied spaces and measured PM and carbon dioxide (CO₂). IAQ sampling confirmed that the implemented risk-reduction measures functioned as intended in most cases. It also provided a quality control check, flagging spaces that did not meet expectations due to system limitations or operational issues. The team addressed these through adjustments to HVAC systems, addition of air cleaners and education of school staff.

The IAQ data also highlighted an opportunity for most school districts to improve the learning environment through ventilation improvements. Older schools consistently had higher CO₂ concentrations in occupied classrooms than newer buildings. While these concentrations were below established thresholds, they are higher than recent studies[3] recommend for optimal cognitive function.

A proactive, evidence-based approach to safe and healthy schools, like that taken by Seattle Public Schools, provides effective results through targeted interventions. Even as the pandemic subsides, improving IAQ in schools needs greater attention to reduce illness and absenteeism due to common and new pathogens. As we continue balancing energy conservation with IAQ, this approach will create better learning environments.

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Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect with over 30 years of experience in sustainable building design. He is a senior consultant with Intertek Building Science Solutions in Portland, Ore. Brendon Mattis, PE, CxA, LEED AP, is an engineering and commissioning agent with 28 years of experience and a principal with EEI in Seattle. To learn more, follow Scott on Twitter @alanscott_faia[4].

Source URL: https://www.metalarchitecture.com/articles/healthy-schools-its-in-the-air/

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