Understanding Air Balancing and How Air Duct Cleaning Can Have a Big Impact on Air Flow and System Efficiency

Posted on 09/28/2021

The comfort and safety of building occupants relies not only on the mechanics of an HVAC system functioning properly — it also relies on the even distribution and flow of air through spaces. During cooler months, occupants desire warm spaces throughout a building, while in warmer months they seek cooler air. Uneven airflow can cause spaces to become uncomfortable, or even unsafe, as particulate, pathogens, or other pollutants build up, while inefficient systems increase energy consumption. 

Air balancing ensures that airflow is even throughout building spaces, providing comfortable and safe conditions for occupants and maximizing energy efficiency.

How Air Balancing Works

Air balancing tests airflow in a building’s ductwork. Most notably, air balancing detects uneven airflow or negative air pressure. Uneven airflow can manifest with rooms not getting adequate heat or receiving too much cold air when the air conditioning is on.

Negative air pressure happens when pressure inside a space is lower than outside. In non-hospital settings, where it is an intentional part of a system, negative air pressure creates unnecessary strain on units because they must constantly pull air to counteract the higher pressure outside.

“Air balancing allows the equipment to be optimized so it’s not over- or under-using energy,” says April Yungen, ASCS, CVI, the founder of Air Management Industries Incorporated in California and 1st Vice President of the National Air Duct Cleaners Association (NADCA) Board of Directors. “Energy is a big reason for air balancing, as well as equipment life span. If it is not working properly, it’s not going last as long.”

Equipment aside, uneven airflow and negative air pressure can make most settings unsafe due to particulates, pathogens, or other pollutants that build up over time.

Where Air Balancing is Important

Air balancing may be performed in residential areas, but is more common in public buildings such as schools and offices.

Some system manufacturers have added Bluetooth and Wi-Fi capabilities to make data capture easier, and many buildings now have control programs integrated into their HVAC systems. But proper air balancing still requires physical measurement and inspection of each grille.

That thoroughness is particularly important in healthcare settings, where air cleanliness, filtration, and airflow are vital to the health and safety of infected or immunocompromised patients. For example, hospitals have a specialized room called an airborne infectious isolation room, where they will place patients diagnosed with any airborne infectious disease. The room uses negative pressure to constantly pull air in, stopping contaminants from escaping. As a result, hospital rooms require the air to be circulated more than other buildings. Measured in air changes per hour (ACH), a typical room undergoes 4 ACH, while a hospital room may have an ACH of 12 or higher.

Why Test?

To perform an air balance test in any setting, a testing, adjusting, and balancing (TAB) specialist uses diagnostic tools to measure the flow of air being emitted from each of the air handling unit’s distribution points to the specifications of the building’s mechanical engineer. The TAB specialist will then submit a report that summarizes the testing and balancing, and note any deficiencies.

While the results of the tests detail uneven airflow and negative air pressure, it also helps a TAB specialist determine causes. For example, air could be leaking out from the duct, or for multi-story buildings, design flaws such as undersized ducts, long duct runs, and runs with multiple sharp turns could be responsible.

Overall, Yungen explains that air balancing is crucial to building owners as it allows them to know that their building meets the specified airflow at each grille or register, meaning the proper air is provided to each space.

Air Duct Cleaning and Air Balancing

Air balancing problems can come in all shapes and sizes, such as HVAC equipment with improper repair work, poor maintenance, and faulty installation of control systems. However, while air duct cleaning technicians’ roles directly assist proper airflow in systems, they still have a part to play in air balancing.

Without proper understanding and training, duct cleaners can affect the air balancing of a room or even a whole building.

“I have heard hundreds of complaints from air balance technicians that duct cleaning does more harm than good because the duct cleaning technicians do not understand the importance of damper position,” Yungen said. “The key to this is training your duct cleaning technicians the importance of air balancing.” 

For example, part of that training would be to have workers mark damper positions before a cleaning project, so the dampers can be moved back to those same positions after the job is completed.


Comfort and safety for building occupants relies not only on the HVAC system working properly, but it also relies on air balancing. Correct balancing will keep occupants warm in the cooler months and cool in the warmer months.

Air balancing is a process filled with variables that require technicians take their time to understand the system and how it works so they can effectively measure all of a system’s performance and, if necessary, provide solutions to the engineer or building owners.

Article originally featured in July/August 2021 edition of DucTales magazine.

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HINT: Article above first appeared in DucTales, and is worth one (1) CEC!!

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