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Engineering the Air We Breathe

Published Monday May 17, 2021

Author Judi Currie

James Vear, quality manager at Yeaton MEP. Courtesy photo.

From the time a heating and air conditioning (HVAC) system is installed to the end of its useful life span, some building owners may never give that system a second thought other than to change the filters, unless it breaks down … or there’s a pandemic.

Modern, airtight, energy-efficient structural design is coming up against the need to get more fresh air into buildings and remove deadly pathogens. Even when many buildings sit empty or only house a fraction of the workers they used to, the HVAC industry has never been more in demand as employers and landlords scramble to ensure safety.

Is the system providing enough outdoor air to meet the ventilation requirements? Is the system in need of any upgrades to enhance the filtration? Can other technology help eliminate particles or stop them from making their way into the occupied spaces? These are the questions engineering firms are being peppered with, says William Gagnon, P.E., a mechanical engineer at Yeaton MEP in Bedford and Littleton. “Building owners, schools and health care facilities especially want to make sure that the employees and the people going there on a daily basis stay safe and healthy,” he says.

Christopher S. Kopec, P.E., regional director of facilities at McFarland-Johnson in Concord, says the first line of defense for any space is to conduct a field review of all of the centralized HVAC equipment to make sure it’s operating properly.

McFarland-Johnson engineer Sydney Seney inspects a recently installed natural gas-fired boiler at the Portsmouth International Airport at Pease. Courtesy photo.

“It’s essentially a systematic review of the HVAC equipment to ensure that it’s functioning as the design intended,” says Kopec. “The best investment a building owner can make is to be sure that the money they’ve already spent on very expensive equipment isn’t going to waste, and the equipment that they have is actually working as efficiently and effectively as possible.”

Jason Urso, project manager at Tighe & Bond in Westfield, Mass. (the firm has an office in Portsmouth), says when they perform ventilation air calculations, they are checking to see if the system meets the latest code requirements and COVID-related recommendations, and compare the results to the way the system is designed to run. “If they are under-ventilated, we do an assessment to see if the system can handle extra outside air,” he says.

Air handlers that draw in outside air use dampers controlled by an actuator that opens and closes the damper. “We are finding in some cases that these dampers are in poor condition, they may be rusted shut, or the actuators that move them are not working,” Urso says.

It’s not uncommon to find the ventilation units within heating and cooling systems bringing in little to no outside air, says Tom Betteridge, P.E., principal and vice president of mechanical engineering at Turner Building Science & Design in Concord. It’s an easy fix in some cases by just opening a damper or changing a setting in the control system. He adds that often the building owner or occupant is surprised to learn they were not ventilating their building.

Tom Betteridge, principal and VP of mechanical engineering at Turner Building and Science Design, with part of the redesigned office air filtration system. Courtesy photo.

“We had one client who mentioned that they used to feel lethargic in the afternoon, and they thought it was just people getting tired,” says Betteridge. After they provided proper ventilation, CO2 was no longer building up in the space, and people felt better.

The possibility of a buildup of virus particles raises the stakes. “Looking at how the current pandemic is spread, increasing, the ventilation air—the clean air that’s brought in and then exhausted out of the space—seems to be one of the most effective ways to reduce the risk of contracting COVID-19. That’s been our main focus,” says Betteridge. “Our secondary focus has been on increasing the filtration levels so that you can filter out the virus particles from the air that remains in the space.”

The American Society of Heating, Refrigerating and Air-Conditioning Engineers, known as ASHRAE, convened a COVID-19 task force to develop guidelines based on CDC recommendations.

“[ASHRAE] is sitting in the driver’s seat figuring out how to architect the future building environment that is most efficient and has the best indoor air,” says Paul Bemis, president-elect of the NH Chapter of ASHRAE and co-founder of the Bristol-based startup, Air Cleaners. “Right now, they’re a bit conflicted themselves because in this stage of COVID-19, you want a lot of fresh air coming in, but the problem with getting fresh air into the room is an energy loss.”

Generations of design have made buildings tighter and more insulated with energy efficient windows and all the cracks sealed and “then this pathogen comes along, and the advice is open all the windows and turn on the fan,” he adds.

ASHRAE recommends meeting air flow rates for ventilation as specified by code, and using combinations of filters and air cleaners of MERV 13 (minimum efficiency reporting values as measured on a scale of one to 20) or better for air recirculated by HVAC systems.

James Petersen, P.E., principal and founder of Petersen Engineering in Portsmouth, says MERV 13 is a higher efficiency filter that removes smaller particulate from the air stream than standard filters but without requiring significant modifications to most HVAC systems.

“There are even more efficient filters than the MERV 13, but they can’t simply be plugged into an existing system,” he says.

“It would require more area and larger fans and would result in a pretty expensive alteration that might not even be physically possible.”

The use of portable HEPPA filters that can be plugged into a standard electrical outlet can be effective for an office, a bedroom or an exam room, he adds.

Flushing and Automation
Another recommendation is leaving systems on longer to get more fresh air into the building before the building is used, as well as after people leave for the day, says Petersen.

Gagnon says automation systems are expensive but are a good upfront investment. “It can help control how often the outdoor air is treated to make sure that we’re flushing the space during occupied hours and ahead of people arriving at the office, but we’re not doing it at midnight on Christmas Eve when there’s no chance of anybody being there.”

William Gagnon, health care team leader at Yeaton MEP, conducts a district-wide assessment for a Southern NH school system. Courtesy photo.

He adds that it is important to consider changes to the way a building is being used since the HVAC system was originally designed and installed. “How has the function of the space changed? What was once a janitor’s closet might be the guidance counselor’s office. Perhaps it wasn’t on the system to begin with, and what do we do about that?” asks Gagnon.

HVAC in Demand
Traci Beaurivage, owner and president of NH HVAC Systems in Hooksett, says at the beginning of the pandemic people expected business to drop, especially with so many office buildings and schools not in use. “It’s been crazy busy,” says Beaurivage, who has more than 30 years of experience in the industry.

One unexpected source of increased business has been cell towers as workers went remote and began using their cell phones more, she says, pointing out NH HVAC Systems services 158 US Cellular tower sites in NH. Each site has two or three AC units. US Cellular and other companies with antennas and devices on the tower have equipment in the building at the base of the tower that has to be kept below 80 degrees. “It’s pretty funny when you get a call in January because someone’s air conditioning isn’t working because they’ve got an excess heat alarm, but that’s how it happens.”

With New England temperatures, she can’t simply bring in 100% outside air as it would be too cold. She says many of her clients have increased the fresh air intake to meet the CDC guidelines but have also turned to emerging technology, including UVC (ultraviolet light) and the Clean Air Curtain made by Air Cleaners (featured in the March issue).

Beaurivage says several private schools have installed UVC systems and are using air cleaning devices, but few NH public schools have chosen to do so. She says there is grant money available, which Amherst is using for some of these improvements. “Why not get the kids back in school? Make the environments healthier, not just for COVID but for everything. We’d see fewer colds. These kill molds. Kids with asthma would breathe better.”

Petersen says UV light is being used more often, but it is complicated. While it is a proven technology, it is not safe for people to be directly exposed to UV, so it is often installed inside air handlers or ductwork. He says the pandemic will probably lead to new UV products coming onto the marketplace, which, unlike the models being used in hospitals, will be suitable for home use or light commercial buildings.

Kopec says up until now, there hadn’t been a real need for such robust systems in non-medical settings, but the pandemic is driving requests for medical grade technology, including spatial pressurization strategies where negative pressure is used to remove air from a space.

Among those examining such systems are airports. In a presentation to the Northeast Chapter-American Association of Airport Executives, Kopec recommended an approach similar to a hospital waiting room, explaining the concourse has many individuals sitting together for an hour or two prior to a flight.

“One of the simple things that they do in a hospital is to keep that waiting room under negative pressure to minimize the exposure of the day-to-day workers outside of that space,” he says. “In the case of the airport, your TSA workers, your maintenance workers and administrative staff at the airport are better protected by keeping that hold area under a negative pressure where we can help to reduce any type of viral concerns outside of that space.”

LEEDing by Example
The longstanding guidelines established by the U.S. Green Building Council (U.S. GBC), which are used for construction projects that want to pursue LEED certification, are perhaps more well known for the environmental advantages and energy reductions they represent; but a central tenant of the LEED certification process has always been that the building be healthy for people.

Gagnon says the LEED criteria is well suited to the pandemic and consistent with the current recommendations for safer spaces. “LEED has always been talking about adding filtration to the building. You get a credit for adding 30% extra ventilation to the space; you get a credit for enhancing the filters and really making sure everything is well flushed,” says Gagnon. “Their research has shown that it adds to productivity and makes for a better building environment. So, I think it’s a happy coincidence that these recommendations and upgrades we’re now pursuing are becoming kind of a common conversation.”

Betteridge says he has always struggled with the huge focus on energy efficiency at the expense of the people inside. “It’s easy to look at your gas or electric bill and say, ‘I saved 50% this month because I made these improvements,’ but it’s harder to quantify that ‘I saved $100,000 this month because my employees were 10% more efficient or the test scores at the school are higher because we improved the indoor air quality.”

He says studies show the benefit, but not everyone is willing to jump on the bandwagon because it’s harder to quantify. “LEED has been around for a couple decades, and the U.S. GBC has been very successful in shining a light on construction materials emissions, and water and energy conservation,” says Petersen. Meanwhile, states such as Massachusetts, where his firm does a lot of work, are raising the bar in response to climate change.

“As a practitioner who’s been interested in energy efficiency for 35 years, there have been moments that have prompted progress,” Petersen says. “In the 90s, the global energy security issues coupled with climate change resulted in LEED  and other building improvement programs, such as Passive House, getting some inertia, and now that the consequences of climate change are more tangible, there is an increased urgency for high-performance buildings in certain cities and states.

Massachusetts is a real leader nationally, and I think the pandemic is going to be another motivator for people to invest time, research and attention to making the indoors a less risky place to be.”

Petersen, whose firm specializes in sustainable, high performance buildings, recommends dedicated ventilation systems that are decoupled from heating and cooling, such as energy recovery ventilation systems. “In the winter, heat is recovered from the outgoing air stream and is exchanged into the incoming stream with very little cross contamination between the incoming fresh air stream and the outgoing exhaust stream. That allows for the ventilation system to provide 100% outside air as opposed to recirculating air. It’s called a dedicated outdoor air system. It is not required by code, but it is a safer way to ventilate.”

Into the Unknown
One year into the pandemic, talk of returning to normal or finding a new normal is giving way to a realization that businesses cannot predict what’s going to happen, and everything that is created and built must have some flexibility.

“Everyone is still in a reactionary phase trying to implement ASHRAE and CDC recommendations to make buildings safer,” says Urso. “The owners are realizing pre-existing deficiencies and just trying to get everything working. I think organizations like ASHRAE, LEED and U.S. GBC have a lot of great design guides right now that make sure the engineering community is designing systems to perform well, reduce energy and increase indoor air quality.”

He adds there may be recommendations that come out of this pandemic, but at the very least, he is hoping building owners realize what is involved with HVAC upkeep and try to formulate a plan to be sure systems are operating the way they should be.

“What might help building owners would be for the engineering community to, in the scope of work, identify the maintenance requirements for these systems. It is easy to design it and have the contractors hand off the operation and owner’s manuals without any guidance to understand what it takes to properly maintain it,” Urso says.

With new construction, Gagnon says, the pandemic has provided an opportunity to share ideas to enhance ventilation.

“Maybe you provide a unit that has better filters built into it, maybe you have something that has a UV light built into the air handling system. These are ideas that we want to float, saying that, as a new construction project, you have the opportunity to be a little proactive about this and be well prepared for the next time.”

Betteridge says the pandemic has led to an increased focus on air quality and its effects. “A lot of the stuff we’re doing now due to COVID-19 we should have been doing it anyway,” he says. “There are so many benefits to the building occupants from increased indoor air quality, such as increased cognitive ability.”

He says an associate professor at Harvard, Joseph Allen, has written several papers on healthy and sick buildings that are getting more attention. “It is the sort of publicity that we didn’t get before. Now everyone is so focused on indoor air quality that we’re able to make some of these changes,” says Betteridge. “It’s our hope and belief that some of these changes should stick and continue because it’s not a huge increase in operating costs, but there’s a massive benefit to the building occupants that has been proven through testing.”

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