Source: The Center for Green Schools
Ventilation has received increased attention over the past two years, especially in schools where our children spend a large portion of their day. One reason for this is because many schools are decades old and still rely on ventilation systems from their time of construction.
School ventilation systems in North America are designed based on ASHRAE Standard 62 which was first published in 1973. Most schools built in Nova Scotia before the 1970s do not have a mechanical supply air ventilation system, instead they either rely on exhaust fans to pull outdoor air into classrooms through windows and cracks in the walls or they rely on opening windows which are generally closed during the winter due to our climate. These systems may be called natural or passive ventilation systems. Schools built over the past 40 years largely have mechanical ventilation systems comprising of a fan, heating coil, filter and ductwork allowing a consistent amount of outdoor air to be supplied into classrooms year around. These may also be called active ventilation systems.
As ASHRAE is responsible for building ventilation standards, it was natural that they prepared Guidance Documents on how to combat the airborne transmission of SARS-CoV-2. Their Guidance for schools says:
HVAC systems are to be inspected for proper operation,
Ventilation is to be supplied based on Standard 62,
Supply air is to be filtered with high efficiency (MERV-13 or better) filters and
In-room air cleaners can be used where the ventilation and/or filtration requirements cannot be met.
These measures can be implemented with minimal impact on building energy use at a reasonable capital cost.
In addition to mitigating the spread of airborne diseases, ventilation provides many other benefits to classrooms - these include improved academic performance, reduced asthma symptoms and reduced absenteeism. Ventilation renovations have been shown to improve math and reading test scores significantly with an improved probability of passing by 2% and 3% respectively. For each 1 L/s (2.2 cfm) per occupant increase in outdoor ventilation airflow rate, illness absence was found to decrease 1.6%.
Nova Scotia, like other provinces has added in-room air cleaners to filter out SARS-CoV-2 and other viruses in older schools but in order to see all the benefits of improved ventilation, the next step is to bring our older schools up to current ventilation standards by adding mechanical ventilation systems. This will come at a financial cost but it will provide significant academic benefits and help shield us from this and future epidemics for years to come.