School HVAC Systems and Covid-19

J&A South Park of Pittsburgh, PA, helps local school HVAC systems and minimizing the COVID-19 spread

A message from your authorized Trane® dealer on School HVAC Systems and Covid-19 . . .

“Bringing HVAC systems in schools up to date will be a key part of improving student health and performance.”

– Rachel Gutter, director of the Center for Green Schools

Is opening a door or window enough ventilation to prevent the spread of Covid-19 in schools?

With last year’s school year cut considerably short by the Covid-19 pandemic, public and private school systems and higher education institutions throughout the nation have been examining strategies to ready their buildings for a safe return to school this fall.

Across the board, schools have been instructed to produce various control strategies, focusing on de-densifying classrooms, increasing physical space, tweaking ventilation, improving filtration, and being concerned with supplemental air cleaning.

Fact is, properly operating and maintained HVAC systems will perform a vital role in producing a secure environment – and in creating trust from staff and parents as these buildings are being returned to.

HVAC systems are critical to Covid-19 mitigation efforts due to their ability to control airborne pollutants and viruses and distribute fresh air in classrooms.

Although the CDC recommendations focus largely on disinfection and social distancing, it offers only brief guidance on school HVAC systems:

“Ensure ventilation systems operate properly and increase circulation of outdoor air as much as possible, for example, by opening windows and doors. However, 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.

On the other hand, the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) provides more robust guidelines to help schools detect explicit opportunities for boosting ventilation. It’s important to note, too, this guidance is being updated on an ongoing basis on the ASHRAE website,, as research evolves.

An article published in 2020 in USA TODAY titled “Ventilation and air filtration play a key role in preventing the spread of Covid-19 indoors” includes important information from experts like Dr. Shelly Miller, professor of mechanical engineering at the University of Colorado Boulder, as well as representatives from the ASHRAE Epidemic Task Force.

The article states that most HVAC systems cycle in about 20 percent fresh air, and the residual 80 percent is recirculated air. This is done to slash energy bills.

However, some aerosolization scientists recommend moving the air out completely and bringing in 100 percent fresh air. That, of course, means greater energy costs. But, let’s face it, the safety of children and students is more important than the extra cost of running the HVAC system.

ASHRAE recommendations for HVAC systems

ASHRAE recommends that the HVAC system provide six complete changes, and it recommends ventilating the room one to two hours before classes are opened and one to two hours after classes are finished.

Every child has a right to environmentally friendly classrooms

On the National Air Filtration Association website, in the section on air filtration for school, it quotes the American Public Health Association: “Every child and school employee should have the right to an environmentally safe and healthy school that is clean and in good repair.” It emphasizes the fact that schools are even more densely populated than a typical commercial building making the “bioburden” much more significant and leading to some of the worst air conditions in any environment.

The truth is, unfortunately, as many as 10 million students and more than 1 million public school employees are engaged in some form of in-person learning may be at risk of heightened exposure to Covid-19 due to outdated and poorly functioning heating, ventilation, and air conditioning systems.

For the most part, this is due to the fact that many of these structures are old, in need of repair, and may even be exposing occupants to other environmental hazards such as carbon monoxide and mold.

GAO report shows the need for system upgrades or replacements

As schools are re-opening in the midst of the lingering pandemic, we’ve seen that HVAC should be at the center of the mission.

Adequate ventilation and effective air filtration are critical elements to help ensure safe indoor air quality for educational institutions.

The challenge is that many schools are housed in older buildings that may not have been adequately maintained. Moreover, there are a wide variety of natural, mechanical, and hybrid mechanical systems operating in schools around the nation. A recent Government Accountability Office (GAO) report estimated that one-third of K-12 buildings that need system updates or replacements, including HVAC and plumbing.

The need is especially pressing for high-poverty school districts that are more likely to rely on state funding to pay for improvements to school facilities and thus are disproportionately impacted by state-level budget cuts – first during the Great Recession and now during the Covid-19 crisis. Building maintenance often receives the largest cuts during budget reductions, meaning that, without targeted intervention, HVAC systems may be under-prioritized at every level.

Transforming these buildings to address the new challenges of minimizing exposure to the novel coronavirus is that much more difficult.

In a recently published article, Christopher Ruch, the director of training at the National Energy Management Institute, said that poor ventilation is an age-old problem that predates the current Covid-19 crisis. Many classrooms did not have HVAC units operating at the minimum required ventilation rates even before the pandemic. The benefits of adequate ventilation, including reduced absenteeism, improved cognitive retention, and improved productivity, have been well documented in multiple publications. This issue needs to be addressed regardless of the Covid-19 pandemic.”

Rajan Goel, a vice president for a building solutions group, echoes these thoughts: “Every school building is different, and there are many aspects to creating safer and healthier indoor environments. From an engineering perspective, filtration can play a critical role in enhancing indoor air quality. In buildings with mechanical ventilation systems, existing filters may be upgraded to filters with efficiency ratings of at least MERV 13. If existing systems cannot accommodate MERV 13 filters, in-room HEPA air filters can dramatically improve indoor air quality.”

Clean air ventilation in school gym because of HVAC system

Why are ventilation systems so important?

Even beyond the pandemic, HVAC systems play a major role in creating safe and comfortable learning environments for students and school staff by regulating indoor air quality and maintaining comfortable temperature levels.

The Environmental Protection Agency has ranked indoor air pollution as one of the top five environmental risks to public health, and health risks associated with poor indoor air quality (including skin and eye irritation, allergies, and asthma attacks) have the potential to impede student learning and achievement directly.

According to a literature review conducted by Lawrence Berkeley National Laboratory, increased ventilation rates are associated with higher student performance in reading and math as well as reduced respiratory health effects and absenteeism.

Safe air circulation is crucial

In the early stages of the pandemic, public health officials believed the coronavirus was spread mainly via droplets – virus-laden liquids larger than 5 microns across. The subsequent rules on social distancing came in part from studies that found a cough or sneeze could project these droplets several feet away, where they might hang in the air for several minutes before landing on a surface.

More recent studies, however, found that Covid-19 spread through much smaller aerosolized particles, which both traveling farther and hanging in the air indefinitely until blown away. That made keeping air circulating safely much more important.

What about aerosolization?

The term “aerosolization” becomes a critical factor here. Pulmonologist Dr. Kevin Fennelly wrote in 2020, “Data show that infectious aerosols from humans exist in a wide range of particle sizes that are strikingly consistent across studies, methods, and pathogens. There is no evidence to support the concept that most respiratory infections are associated with primarily large droplet transmission. In fact, small particle aerosols are the rule, rather than the exception.”

This was a tremendous leap forward in the understanding of the pandemic. It confirmed that preventative measures had to address this critical issue: the ventilation of indoor spaces. While the concept of contaminated surfaces and respiratory droplets dates back 100 years ago, it’s only recently that we’ve had the ability to identify how respiratory pathogens work.

One other study of the coronavirus in buildings found that because of the viruses’ transmissible tendency to hang in the air, school administrators might not be able to rely on the normal rate of airflow from their ventilation systems to clear virus particles from the air. And a separate study of Dutch schools found aerosols built up steadily in school gyms even when they had ventilation. Still, the combination of increased ventilation and the use of mobile air filters cut the concentration of aerosols in the rooms by 80 to 90 percent.

Low-income schools and schools serving minorities

It’s important to note at this point that not all students experience poor learning environments to the same extent. Low-income schools and schools serving people of color and indigenous students are more likely to have unhealthy conditions due to significantly lower funding compared to schools with predominantly white student populations, and because they are often located in neighborhoods with poorer air quality and greater levels of noise.

For example, based on a study of nearly 85,000 public schools (grades K-12) across the nation, students from racial-ethnic minorities disproportionately suffer from exposure to air neurotoxins in school and pose health risks, which can also impact school performance and future potential.

HVAC systems help clean air in school classrooms

Facts & stats about HVAC in schools

  • About 50 percent of our country’s schools have problems related to indoor air quality.
  • Children are more susceptible to indoor pollutants.
  • Students start to learn less when the temperature surpasses 70 degrees. The hotter the classroom, the worse the conditions for learning.
  • Energy is the highest school-related expense for states besides staff.
  • Schools that make energy efficient improvements slash utility bills by 5 to 20 percent.

Creating healthy buildings

As we’ve seen, one key to keeping students and staff safe is reducing the risk of airborne transmission of the virus. The Harvard Healthy Buildings team recommends that schools prioritize minimizing indoor air re-circulation and maximizing fresh outdoor air as much as possible.

Air filtration is key when the total elimination of recirculated air cannot be achieved, but installing higher-grade filters, such as HEPA filters or those rated MERV 13 or higher, is too costly for most districts to do on their own.

Conducting routine building maintenance, including testing ventilation and filtration performance and frequently replacing filters, is essential for maintaining efficient systems that promote good indoor air quality and yield cost savings. Yet even this level of service can be beyond the budget of many schools.

Trane® Technologies offers solutions

In response to these circumstances, Trane Corporation has offered a comprehensive suite of solutions to address conditions and recommendations across all four critical pillars of indoor air quality, including cleaning the environment to actively reduce the number of microbiological that may be in the air or on surfaces. Air cleaning technologies range from high-rated MERV or HEPA filters to Ultraviolet Germicidal Irradiation and photocatalytic oxidation.

“As schools bring back students for part-time or full-time in-person learning, healthy indoor air quality is a chief concern alongside other safety practices including wearing masks and social distancing,” said Donny Simmons, president, Commercial HVAC Americas at Trane Technologies. “HVAC systems, properly applied, are an important aspect of addressing environmental concerns within a school.”

For further information on the importance of HVAC systems in our schools, don’t hesitate to get in touch with your HVAC professionals at J&A South Park.

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