A recent study conducted by UC Davis and Lawrence Berkeley National Laboratory researchers found that 85% of the heating, ventilation and air conditioning, or HVAC, systems in California K-12 classrooms do not provide sufficient ventilation.
The study found that many of the HVAC systems had equipment, fan control or filter maintenance problems, according to Rengie Chan, study author and deputy chemist of the Berkeley Lab Indoor Environment Group. Lack of sufficient ventilation, Chan explained, can lead to adverse health effects.
“Inadequate ventilation in classrooms is a very common problem,” Chan said in an email. “There are compelling evidence of an association between inadequate ventilation impacting student performance, resulting in respiratory health effects, and student absence.”
The study inspected 104 classrooms across 11 schools in California, all of which had new HVAC systems installed within the last three years. Data was gathered through field inspections, monitoring and a teacher survey. Indoor environmental parameters were measured for four weeks, Chan said in the email.
Classrooms with insufficient HVAC systems were also found to have higher carbon dioxide levels and lower ventilation rates. Increasing evidence has shown carbon dioxide is associated with the ability to perform cognitive tasks, according to a Berkeley Lab article.
Twenty-three of the classrooms inspected had a temperature above 25.6 degrees Celsius, or about 78 degrees Fahrenheit for more than 20% of school hours, according to the study.
The study also cites prior research showing a recommended range of 20-23 degrees Celsius or 68-73.4 degrees Fahrenheit, for an optimal learning environment. In contrast, only five of the investigated classrooms maintained a temperature lower than 20 degrees Celsius for more than 20% of school hours.
“Many classrooms in this sample were frequently too warm to support learning,” the study said, citing previous research that found a high correlation between student test scores and indoor temperature and ventilation.
According to Berkeley Unified School District, or BUSD, spokesperson Trish McDermott, the study’s findings are not applicable to BUSD schools as the district follows the Uniform Building Code and the Building Energy Efficiency Standards, or Title 24, requirements.
Carbon filters, replaced twice annually, are installed at BUSD schools where exterior air is drawn in. Preventative maintenance and filter replacement are priorities in the district, McDermott said in an email.
“Like many California school districts, we find ourselves facing sustained smoke events — extraordinary circumstances for which schools were not designed,” McDermott explained in the email.
The research team recommends improved monitoring over HVAC purchases and installations to ensure they work properly, Chan said. In addition, routine filter maintenance needs to be provided.
“Classroom ventilation problems can easily go unnoticed, without periodic testing of ventilation systems, and without continuous real-time CO2 monitoring,” Chan said in the email. “We need better detection to correct ventilation problems.”