Ductwork Makes Banging Noise: Causes & Solutions

image of homeowner covering ears due to loud hvac ductwork noises

Central heating and cooling systems produce warm or cold air in one area and then distribute it throughout the entire building using a system of ductwork. HVAC air ducts are frequently comprised of metal which makes them prone to causing noise with even the most minor disturbances. This ductwork noise can be a source of frustration for homeowners when it’s constant or excessively loud. It can even keep residents from sleeping well. Read on to learn why ductwork noise occurs and to learn a few strategies for preventing or reducing it.

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Common Causes of Ductwork Noise

HVAC air ducts can become noisome and annoying due to various reasons. Listen to your ductwork closely to determine which sounds are being produced. Even if you’re unable to see the source of the problem, you may be able to identify it based on the sounds that you hear. One type of noise that we frequently encounter is loud, banging sounds.

Banging Sounds Coming From the HVAC Ductwork

Sometimes homeowners report hearing loud banging and popping sounds inside of their HVAC air ducts. This type of noise usually occurs in quick, short bursts. It is the result of expansion and contraction in the duct walls as internal temperatures rise or fall. This type of noise can also be the result of pressure changes within the ducting. Keep in mind that ducts expand when exposed to hot air, and they contract when exposed to cold air. These changes may be imperceptible to the naked eye, but you’ll likely hear them occurring in real-time just after you’ve turned your home cooling system or heater on.

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Common Causes for Other Forms of HVAC Air Duct Noise

Banging and popping sounds aren’t the only type of noise that HVAC ductwork can make. Following are a few common sounds and their most likely causes.

Ductwork That Rattles

image of rattling hvac ductwork

If your HVAC ducts are producing rattling sounds, then the most likely cause is the movement of loose metal parts. These components knock into each other and make audible sounds. This is a common problem in aging ductwork. Seals start to fail, and various connections loosen as the result of static pressure. This is a noise that you’ll continue to hear so long as there are loose components and air moving through your ductwork. It might start off as relatively soft, but it will eventually become so loud that it’s impossible to ignore. A licensed HVAC company can identify and resolve the underlying issue.

Booming Sounds in HVAC Ducting

Booming noises may be heard at the meeting of the duct’s plenum and trunk. The largest changes in temperature occur in this very area. If there are insufficient dampers or expansion joints at the connection, the sound will reverberate throughout your entire home via the supply ducts. Skilled HVAC equipment installations understand the potential for this issue, and thus, they take steps to limit noise from the connection.

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Shaking Ductwork

There may come a time when you see your air ducts vibrating or shaking and producing a low home. This is a problem that occurs when airflow is blocked on the return side as the result of a dirty, dust-covered air filter. Given that air is unable to enter, the pressure falls so low that the ductwork starts to vibrate and shake. Make an effort to regularly check your air filters. If they start looking dirty, replace them or clean them as required. Your HVAC ductwork will produce far less noise, and your HVAC equipment will be far more efficient overall.

Scratching Noises Within HVAC Air Ducts

image of a rat in hvac ductwork

There is another unpleasant noise that your air ducts can emit. This sounds like something or someone is scratching on the metal walls of the ducts – and there is a very likely chance that this is squirrels, raccoons, rats, or other animals that have found their way into the system. Take immediate actions, or pests may start making nests and settling in, negatively impacting your indoor air quality and causing other issues. If you hear loud buzzing sounds, this could be a bee or another large insect. Get help from a local HVAC company.

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How to Keep Noise in Your HVAC Ductwork to a Minimum

Ductwork noise isn’t something that homeowners always have to contend with. Loose objects and pests can be taken out. Competent HVAC professionals can repair damaged areas. As for the sound that results from normal use, you can even reduce these to make them softer and easier to bear. Following are a few ways to do this:

Adjust the HVAC Fan Speed

During the installation process, HVAC professionals determine the amount of HVAC airflow. Every heating or cooling system has its own ideal range that’s determined by various factors. In some cases, installation companies may set this speed far higher than it needs to be. If this is an issue in your home, you can reduce static pressure by lowering the fan speed. You might want to have an HVAC technician help you with this because lowering the fan speed too much will make it virtually impossible for conditioned air to reach every room in your home.

Change Out Your HVAC Air Filter

image of a dirty air conditioner filter that needs replacement

Keep a close eye on your HVAC air filters. These components are meant to capture and collect dirt and other airborne particulates while still allowing air to flow through. The more debris that they retain, the more that air struggles to pass through them. Air filters must be replaced at least once every two to three months to keep airflow optimum and to ensure overall efficiency. However, homes that have pets or that exist in naturally dusty areas often need to have their filters replaced monthly. The ideal frequency for HVAC air filter changes depends upon the nature of your living environment and many related factors. Clean filters will limit the likelihood of clanging, banging, and popping sounds in your HVAC air ducts. Air filters don’t cost a lot, so you should stop up to keep your home heating and cooling equipment working and sounding like it should.

Have Larger HVAC Air Ducts Installed

Consider the fact that your HVAC air ducts may be too small to handle the amount of air that your heating and cooling equipment requires to function well. Even though your heater and air conditioner might be the right size, you can still have a number of problems if the air ducts are too small. Having larger air ducts installed may reduce the amount of noise that you’re hearing as will a larger supply and return plenum. When paired with high-velocity grilles and registers, you’ll get better airflow all-around.

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Have a Bypass Duct Added In

If you have a multi-zone system with excess pressure, you may be able to lower it by having a bypass duct installed. Pressure mitigation strategies like this one will limit the amount of stress that your ducts are subjected to and prevent many other issues. However, this is a strategy that only works in specific instances. Speak with an HVAC company to see whether having a bypass duct installed is the right choice for your home.

Consider Different Duct Shapes

hvac ductwork installation

If it’s time to have new ducts installed, think about getting a different duct shape. Rectangular ducts are becoming increasingly popular due to their clean lines and sleek profiles. However, these ducts create more noise than round ones due because they don’t tolerate pressure as well. If your home can accommodate round air ducts, then this is an option worth considering. Get advice from an HVAC technician.

Install a Duct Silencer

If you have round ducts, a duct silencer or duct muffler can b installed to limit the amount of noise they create. Duct mufflers have built-in insulation and a double-wall design that helps mute their vibrations. These components work best when they are positioned near an air handler, the fan, or any other component that makes a significant amount of nose. Keep in mind, however, that they are only able to reduce noise. They cannot entirely eliminate unwanted sounds.


Have Your Ducts Insulated

You can have insulation wrapped around your ducts to make them more energy efficient. This will also minimize the amount of noise they produce, especially popping or banging noises. For best results, have this job handled by a licensed HVAC technician.

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Consider Having a Ductless System Installed

If you’ve already taken advantage of all of these noise reduction strategies and are still unhappy with the amount of sound coming from your ductwork, you may want to bypass the use of ducting completely. Think about switching to a ductless mini-split setup to minimize maintenance and reduce unwanted sounds. You’ll have the additional benefits of zoned heating and cooling, greater energy efficiency, and independent temperature control.



Ductwork noise can mean many different things. At times, this is an indication of a problem like incorrect configuration, pest issues, or loose parts. Ductwork noise may be an indication of a need for immediate attention. However, noise may simply be a normal part of your system’s operation. It may not be possible to eliminate unwanted noise, but you might be able to reduce its frequency and volume of it. Speak with a reputable HVAC company to find out which solution will work best for your home.

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