You Need to Balance Your HVAC System

When certain rooms in a home are consistently warmer or cooler than others, there may be an obvious cause, like an uninsulated exterior wall or drafty windows. But that’s not always the case.

If you’re unable to determine what’s behind the temperature difference, there’s a good chance that your home’s HVAC system needs to be balanced. Air balancing is an essential part of maintaining effective circulation and air quality throughout your home. To better understand this process and why it’s important, Lifehacker spoke with four HVAC technicians and specialists. Here’s what they told us about HVAC balancing, including how to make some DIY adjustments, and when to call a professional.

What is air balancing?

Balancing an HVAC system (or simply “air balancing”) refers to the process of making adjustments in order to optimize a home’s heating and cooling system, and ultimately, making it more efficient, says Jimmy Hiller, president and CEO of Hiller Plumbing, Heating, Cooling & Electrical.

“The primary goal of air balancing is to ensure the even distribution of air throughout the home, leading to consistent temperatures in all rooms,” Hiller tells Lifehacker. The process involves making sure each room receives an appropriate amount of heated or cooled air based on its size and usage, he explains.

What are the signs an HVAC system needs to be balanced?

According to all of the HVAC experts we spoke with, the telltale sign that your HVAC system needs to be balanced is uneven heating and/or cooling in different areas of the home. In other words, certain rooms or areas being consistently warmer or cooler than others without a (separate) clear cause.

“If you walk into a room in your house and it feels like the temperature dropped five degrees, this could be a sign of a draft, but it could also be a sign of an HVAC system that just needs to be balanced,” says John Gabrielli, owner and founder of Air Temp Solutions.

Noises like whistling vents or loud air handlers may also be a sign of imbalances in an HVAC system, says Hiller. “Balancing the system can help reduce these noises by ensuring that air flows smoothly through the ductwork,” he explains.

What causes HVAC system imbalances?

Temperature imbalance can be due to various factors like the distance from the HVAC unit, the size and layout of the ductwork, or the natural heat gain/loss in different parts of the home.

“Over time, ductwork can become blocked or begin to leak out air,” Gabrielli tells Lifehacker. “Changes in the home, like renovations or additions, can also alter airflow patterns.” Hiller adds shifts in foundations and insulation to the list of changes in a home’s dynamics that can lead to a home’s original HVAC design no longer being optimal.

In other instances, a closed supply register may be the culprit. “A homeowner that closes supply registers may unintentionally reduce total system airflow, which can stress the blower motor,” says Jennie Bergman, senior product manager of Indoor Air Quality at Trane Residential. “This can lead to increased energy usage, and ultimately, may cause premature system failures because of the excessive wear on the HVAC system.” According to Bergman, a closed supply register has a similar negative impact on HVAC system performance as a dirty or clogged air filter.

Why is air balancing important?

As we discussed above, a balanced HVAC system is necessary for even airflow and consistent temperatures throughout the areas of your home. But, as Hiller and Gabrielli explain, air balancing is essential for reasons beyond comfort. Let’s start with those related to money.

“An unbalanced system can lead to inefficiencies, causing the HVAC system to work harder than necessary to maintain the desired temperature,” says Hiller. When your HVAC system is forced to work harder, it will lead to increases in energy consumption, and, in turn, utility bills. And because it’s overworked, this puts extra strain on the system, which could result in components breaking down more frequently and requiring costly repairs, potentially shortening its lifespan.

It could also cost you when you decide to sell your home. “Regular air balancing is important for preserving and potentially increasing the value of the property, as a well-maintained HVAC system is one of the key features that potential buyers look for,” Hiller explains.

But that’s not all: HVAC system imbalances could also end up harming your home, or even your health. “Proper air circulation is essential for maintaining good indoor air quality,” says Hiller. “An unbalanced system might not effectively circulate air in certain areas, leading to issues such as moisture accumulation, mold growth, or stagnant air.”  

How to balance your HVAC system

As the experts have explained, air balancing is a process that involves making adjustments to various parts of your HVAC system to improve its efficiency. Like most processes, there are usually a number of different steps—some of which are more difficult than others.

In this case, there are many complicated aspects of HVAC system balancing that should only be done by a professional. However, there are also some relatively simple DIY adjustments you can try making first. While these adjustments aren’t going to fix every possible problem, they may take care of yours and are worth trying before calling a professional.

Check the filters

Even if you’re already changing your HVAC filters on a regular basis, you’ll need to do it again. “Whether you or an HVAC technician will perform the balancing, it should always start with checking and replacing filters, because dirty air filters can restrict airflow,” Hiller explains. And according to Chris Winters, a tech content specialist at Cielo WiGle Inc. with five years of experience as an HVAC technician, clogged filters can also cause uneven temperatures. “Clean [your HVAC air filters] every two weeks, and replace [them] every three to four months for optimal performance,” he tells Lifehacker.

Inspect the vents

Next, check all of your home’s air vents—meaning the supply vents (i.e. the ones that blow heated or cool air into your home) as well as the return vents (i.e. the ones that pull air from the rooms in your home and return it to the HVAC system), Hiller advises. Make sure that the vents are open and unobstructed.

Clean the vents

If you notice dust and dirt in your air vents—including stuck in their cover or grille—it’s time to clean them. This 2021 Lifehacker post walks through the various steps in the cleaning process.

Sometimes you might get lucky and figure out that a particular room or area was too hot or too cold because one (or more) of its air vents was switched off, or that a piece of furniture, other large object, or an obscene amount of dust and dirt was blocking it completely. If that didn’t happen, move on to the next steps. (Or, if you’re nearing the end of your technical expertise and/or patience, it may be time to call a professional.)

Do a temperature check

While the HVAC system is running, check the air vents in each room. First, make sure air is blowing out of the each supply vent. If it’s not, double check the vent to see if it’s actually open. If it’s open, but there’s no airflow at all—or it’s extremely low—make a note of it: You’ll probably need to call an HVAC technician, and this way, you’ll be able to let them known which vents aren’t working.

If there is air blowing out of the supply vent, use a thermometer (we recommend an infrared thermometer) to check and make note of its temperature. When you’ve hit up all the vents in your home, review the airflow temperatures, identifying rooms or areas that are too hot or too cold.

Find and adjust the dampers

The next step in DIY air balancing involves your HVAC system’s dampers. According to Hiller, many systems have dampers in the ductwork that can be adjusted to control the airflow to each room.

But before you adjust the dampers, you have to find them. “To locate the dampers, follow the ductwork from the furnace,” Hiller explains. “Dampers are typically located where the ducts branch off from the main line.”

If you don’t already know which ducts supply the air to the various rooms and areas in your home, you may need someone to check the airflow coming through the supply vents and let you know whether there are any changes when you adjust a particular damper. The process is similar to figuring out which breaker controls the electricity on an outlet or switch, and also involves some trial and error.

To adjust your HVAC dampers, you’ll need to rotate the levers outside the ducts. As Winters explains, moving the lever will either open or close a metal disk inside the supply line that controls the airflow to different parts of your home. “Rotate the lever for maximum airflow, keeping the metal disk flat, and be mindful that an upright position blocks airflow,” he notes.

Now that you’ve figured out how to make the adjustments, refer back to your list noting the temperature of the air coming through the vents of each room.

“Slightly close the dampers in rooms that are receiving too much air—usually the ones closest to the HVAC unit—and open them more for rooms that are not receiving enough,” says Hiller. “Make small adjustments, about 10 to 20 percent at a time, and wait a day or two to observe the impact before making further changes.”

Over the next few days, monitor the temperatures in each room, and continue making further adjustments to the dampers until you achieve balanced airflow. “Remember: Each home and HVAC system is unique, so what works for one might not work for another,” says Hiller. “Be patient and prepared for a bit of experimentation to achieve the best results.”