What Is Air Balancing, and How Does It Work?

Central HVAC systems, such as those with air conditioners, heat pumps, and furnaces, have ducts to deliver conditioned air. That duct network must be balanced to distribute the air optimally throughout the home. If there’s an imbalance, it can manifest in a wide range of symptoms. Air balancing is the process through which a technician identifies and corrects those balance issues.

How to Tell If Your Central HVAC System Is Out of Balance

Increasing energy consumption is often a telltale sign that you’re dealing with imbalance. It’s a reason experts recommend tracking your energy usage month to month and year to year. You likely have a balance issue if you experience a 2-degree or greater difference between floors or rooms. Another sign is that you can feel the difference in airflow between vents or have any vents that make a whistling sound.

The Steps of Residential Air Balancing

There are potentially five phases to the air balancing process. Your technician must:

  1. Calculate the HVAC load
  2. Test static air pressure and airflow
  3. Perform maintenance if applicable
  4. Make adjustments to the system
  5. Finalize the balancing

Home Load Calculation

If you’re having a new HVAC system installed, your technician will perform this step early on. It’s an integral aspect of sizing an HVAC system. It’s also necessary when performing air balancing for an existing system. The technician needs to verify that the original installer sized the equipment appropriately for the home.

The size also dictates total airflow. A 3-ton AC, for instance, should provide 1,200 cubic feet per minute (CFM). This information will be important during the testing and adjustment phases. The technician must also determine the optimal CFM on a per-room basis. It varies from room to room based on the total size, including ceiling height.


During this step, your technician determines if there is an imbalance and, if so, where it is. The equipment used includes a manometer to test the air handler’s static air pressure. A capture hood, also known as a balometer, detects CFM coming from the vents. Your technician may also use a rotating vane anemometer, velocity matrix, voltmeter, and tachometer.

The technician will detect the total airflow of the entire system. In the 3-ton AC example, it should be 1,200 CFM. If the fan is providing more or less CFM than that, there’s imbalance. Once the system airflow is correct, the technician will detect airflow at each vent. The goal is to get each room as close as possible to the optimal CFM determined in the first step.

In rooms that have one vent, all the needed CFM must come from that vent. Those vents must combine in rooms with two or more vents to provide the necessary CFM.


If there are static air pressure and airflow issues that point to a duct problem, your technician will inspect the ducts. This includes an exterior inspection plus an interior inspection using a camera system. There are several potential issues that you’d have to correct before air balancing could continue.

It’s possible to use an air filter with too high a minimum efficiency reporting value (MERV) rating. Another possibility is that the filter is dirty. In either case, the airflow restriction is a problem, and your technician will need to replace the filter.

If dust has accumulated in the ducts to the point of impeding airflow, your technician will need to clean the ducts. Another issue is air leakage. It can waste as much as 40% of your heating and cooling if severe enough. Maintenance may include replacing mounting hardware and reattaching duct sections. The seals between ducts can also break down over time. To resolve this problem, the U.S. Environmental Protection Agency (EPA) recommends the aerosol duct sealing method.


Adjustment begins with the blower. It’s what dictates the total CFM. If total airflow is too high or low, your technician can often fix this by adjusting the fan speed. There can also be fan issues that require repair, such as replacing a ball bearing, or maintenance, such as lubrication.

Once total output is optimal, your technician must go room to room and test vent airflow. When airflow is too high, the technician must lower it to the correct value. If the system has dampers, the technician will fine-tune these to achieve the right airflow. If the system does not have dampers, your technician may need to install them for the rooms that are getting too much air.


The final step is to ensure that the overall balance is correct and sustainable. This involves double-checking all the calculations and retesting the static air pressure and airflow. The technician will test static air pressure at the air handler and at each vent. If that checks out, the technician will also test the total system CFM and the airflow at each vent.

If you have a zoned system, the technician will also check the automated operation of the dampers. If there are any issues there, they can cause air balance problems later when you adjust the system.

The Benefits of Air Balancing

There are four core benefits to optimal balance in an HVAC system:

  • Improved indoor comfort
  • Enhanced energy efficiency and lower costs
  • Better indoor air quality
  • Longer HVAC equipment lifespan


Balance ensures your ideal temperature throughout the home or in each zone. Imbalance will at the very least cause hot and cold spots in certain rooms. If the imbalance is severe enough, it can manifest as one room being several degrees warmer or cooler than another room.

Energy Savings

The U.S. Department of Energy (DOE) estimates that the average household loses 25% to 40% of heating and cooling through the ductwork. With air balancing and, if necessary, duct resealing, you can reduce that loss to 4% to 5%. That’s hundreds of dollars a year in savings and a notably smaller carbon footprint.

Indoor Air Quality

The EPA warns that indoor air quality (IAQ) is a leading environmental health concern for Americans. Imbalanced ducts can be a major contributor to poor IAQ. Proper balance ensures that any dust settles in the ducts rather than recirculating. You can then schedule duct cleaning as needed to remove that dust.

System Longevity

If you have an air imbalance, your system is working harder than it needs to. That results in higher costs in the short term. It also leads to higher costs in the long term because your system will likely need more repairs. There is also additional wear and tear that will shorten the lifespan of the system.

Professional Air Balancing in Etters

Ready & Able Plumbing, Heating & Air has served Etters, PA, and the surrounding areas since 1998. Our HVAC technicians perform air balancing and clean and seal ductwork. We specialize in gas furnaces and boilers, geothermal and air source heat pumps, central air conditioners, and ductless mini-splits.

Our team installs thermostats, carbon monoxide monitors, UV disinfection systems, and whole-house air purifiers, dehumidifiers, and humidifiers. Our plumbing team performs gas, water, and sewer piping. Our plumbers clean drains and hook up appliances. They also install and repair fixtures, water heaters, well systems, garbage disposals, backflow detection, and water treatment systems.

Contact us today to schedule an appointment or get answers to any questions about the services we offer.

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