Working distantly this summer, our staff and board members started to wrestle with the question: “How do we safely reopen a school during a pandemic?” And so began Campus Manager Karen Bridgeo and Board Member Frank Grossman’s journey towards understanding the relationship between airflow and airborne vectors.
Harvard TH Chan report
“Through the course of researching our air quality mitigation strategies,” says Karen, “we spoke with our building architect, the engineer who designed our mechanical systems, and the president of the Granite State chapter of ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers).” The process took most of the summer. “We based our plan on the Harvard TC Chan School of Public Health study, ‘Risk Reduction Strategies for Reopening Schools, COVID-19.’ Lastly, an industrial hygienist reviewed the final draft of our mitigation plan before it was released to our parent community.”
Research indicates that airborne transmission is the primary manner in which COVID-19 is spread, so the school focused considerable energies and resources on airflow in our classrooms. By creating and implementing strategies to consistently introduce fresh air and prevent air stagnation, we worked to ensure our classroom environments were less likely to host concentrated viral loads. This focus was aimed at potentially reducing airborne transmission in the event of an unknowing, asymptomatic, COVID positive person being present in the classroom. The airflow plan was created in tandem with numerous other school-wide strategies and procedures, all designed to enable our students to attend school in person for as long as possible.
Hollis Montessori’s founders decided to build a Passive House building as part of the school for energy efficiency and sustainability. This year we discovered that the same features that make the building efficient also make it easier to prevent the spread of COVID. Each classroom in the lower school is equipped with a classroom-specific air exchange unit that supplies fresh outdoor air. Although the HVAC units recirculate air, it is only within each specific classroom, so there is no cross-contamination between classrooms.
Students working socially distanced while a HEPA filter quietly does its job in the background.
Part of what Karen and Frank learned about airflow this summer is that even in a well ventilated room, there will be areas where air tends to circulate less, similar to a river eddy. After performing tests to identify areas of low circulation, additional portable HEPA air-cleaning units were added to account for the identified pockets of low circulation.
Humidifiers and hygrometers were added to every classroom. Frank and Karen learned that potential infected droplets in the air will fall to the ground in correctly humidified environments, as well as supporting healthy airways for staff and students. Dry air can actually cause infected droplets to aerosolize, which keeps infectious particulates floating in the air. Our electrostatic sprayer, used daily to sanitize, mitigates for any droplets that may fall to the ground.
In addition, the architecture of the Lower School lends itself well to mitigate airborne disease! Classrooms have exterior entrance doors and ample windows to provide additional fresh air, complementing the air handlers. High ceilings also allow for larger air volume, which further dilutes any viral concentration, if present.
Our Middle School is housed in a building that was originally built to house migrant workers when the property was an apple orchard. Because it is a renovated older building, it doesn’t have the same efficient properties as the main school building. However, it turns out that can be a good thing, too. Since the building is “leaky,” the volume of fresh air coming in and circulating throughout the building is higher than in an airtight modern building. To increase that volume, we added an efficient attic fan to pull fresh air in, move it through the building, and expel it out through the attic soffits. Adding oversized HEPA air-cleaning units and humidification to every room in the building also complements the mitigation effects of increased airflow, as well as a multitude of vented windows.
Hollis Montessori has always encouraged our students to spend as much time outdoors and in nature as possible, and this year has been no exception. Outdoor classrooms were in use throughout the fall, as well as many long walks through the woods being incorporated into various programs. Score one for nature - and for virus prevention!