Ventilation is the introduction of outdoor air into an indoor space, and it has evolved over time. Some of the first research on the topic was done by James Billings, an 1870s Johns Hopkins researcher and physician who postulated that carbon dioxide (CO2) was an accurate measure of impurity emissions from the human body. He determined that there needed to be a certain amount of fresh air brought indoors to keep people healthy. Additionally, he also advocated for 60 cubic feet per minute (CFM) per person. Billings' findings hold up today, as most physicians, doctors and health professionals say the optimal ventilation rate is 50-60 CFM per person. However, there’s pushback to implementing such a high ventilation rate because of the associated energy penalties. Indeed, this point was hammered home during the oil embargo days in the late 1970s when energy prices skyrocketed. At that time, according to the National Institute of Health (NIH), the industry went from 20-30 CFM per person down to five CFM per person to save energy. Fortunately though, the HVAC and engineering communities realized that such a low ventilation rate promoted serious health issues—some reversible and others irreversible—due to deficient indoor air quality (IAQ). Thus, in the mid-to-late 1980s, there was a change when the importance of cleaner and healthier indoor air for occupant health and wellbeing became clear. What’s more, attention grew toward ERVs as an effective means to reduce ventilation energy use and costs. The criticality of high-quality indoor air was hammered home in the last 36 months due to the COVID-19 pandemic. Agopian noted, “IAQ has an immediate value. We know that there could be something in the air that you can’t see, breathe, taste or touch that could technically kill you in two weeks. We need to understand that the quality of air has a direct and proportional impact on the quality of our lives.” He also explained that test scores in schools can improve anywhere between 12-18% if CO2 is lowered within the space. Further, better IAQ supports improved sleep and increased productivity. Indeed, he said that RenewAire practices what it preaches and provides a high CFM rate throughout the entire building. In some spaces, such as the training center, cafeteria and gym, there’s absolutely no air recirculation. For Marks, he places a high value on having healthy IAQ for his family at home where his ventilation system brings in as much fresh air as possible. Marks said that in his residence he does 40 CFM per person, which is a tremendous amount of air. He stated, “I have two young daughters and I want them to be healthy and I want to make sure they’re breathing the best-quality air possible. That’s what I do for work so it only makes sense that I do it also for my kids. I would encourage other people to do the same thing because you might be surprised at the poor quality of your indoor air.” Marks summarized the four different ventilation strategies for homeowners to enhance IAQ: • Natural ventilation: This is the easiest option, which can be done by opening a window. • Exhaust-only ventilation: You can pull air out using an exhaust fan, typically via a bath fan, and air will reinfiltrate via any openings in the structure. • Supply-only ventilation: This is referred to as mechanical ventilation where you’re bringing air into a structure and letting it seep out through little micro-openings inside a home. • Balanced ventilation: You’re pushing in high-quality filtered air and pulling out air at the same time. Essentially, you’re controlling the point of ingress and the point of exhaust for the air. Agopian followed up by saying that when we look at exhaust-only ventilation, back 20-30 years ago it was a different story because sealing integrity wasn’t as tight as it is today. There were openings around windows or doors that provided direct access to the outside. So, when you exhausted and depressurized a structure, air would come inside under the door or between cracks in the windows. He continued saying that today, because of the tremendous sealing integrity of structures, air can no longer come through those direct openings. Instead, what you have now is air coming through the structure via a complex path in between studs, through the walls and over and in between insulation. Thus, you’re bringing in air that used to be clean but might not be so anymore. Agopian then said that balanced ventilation is the assured way of replacing one cubic foot of stale indoor air with one cubic foot of fresh and clean outdoor air. He stated that this is the only way to guarantee a positive displacement of internally generated contaminants. When deciding on a particular ventilation strategy, another component to consider is if energy recovery should also be applied. Many people see it as an additional cost, but this isn’t the case. Agopian explained why, “With energy recovery, you’re recapturing the energy that you spent a lot of money on to cool and dehumidify or heat and humidify the outdoor air coming inside. So, when you look at balanced ventilation with energy recovery, we have paybacks that can be as little as two years to about four years. When considering a structure like a home, office building, condo, school or whatever it may be, these structures are built to last 25+ years. Thus, you have an initial cost for the first two to four years and after that the energy recovery system pays you back.” Taking the case further, Agopian stated “60 CFM is what we need in order to be healthy and productive within the built environment, in which we spend 90% of our time. But how do we rationalize that? How do we go from 15-20 CFM per person up to 60 CFM? The best way to achieving that goal while maintaining energy-code requirements is balanced ventilation with energy recovery applied.” Adding to this point was Marks. “I do 40 CFM at home, but I also do energy recovery so I don’t have to pay the huge penalty. I value fresh air tremendously, especially for my kids. That means I’m bringing in more air, and more air means more energy recovery. Thus, if you value fresh air you’re going to want to recover energy as well.” Closing out the podcast was Agopian with a quote from a study by Lawrence Berkeley Lab: “Overall, the number of reported statistically significant improvements in health with increased ventilation rates far exceeded the anticipated chance improvements in health.” What does this mean, asked Agopian? He said this shows that increasing ventilation will improve your health similar to other positive activities. Agopian concluded, “I’m not saying stop going to the gym, don’t eat well or only sleep two hours a night. What I’m saying is keep those up and increase ventilation as well because it gives you just as much of a health benefit.”
