Banging is one of the most common noises heard from HVAC ductwork. It is caused by the expansion and contraction of metal duct walls as pressure and temperature in the system change. Ductwork is therefore prone to making noise any time you turn on the AC or furnace. But that doesn’t mean there’s no answer to the question “how do I stop my ductwork from banging?”
These are some simple ways you can stop ductwork noise:
Clean or Replace the Filter
A dirty filter will decrease airflow, causing an excess of heated air that bows the ducts outward. The pressure will decrease once the heating cycle stops and the metal panels will ‘bang’ and ‘pop’ as they contract. To reduce the noise, clean or replace the filter as needed, and check it every month during the heating season. Install the right-sized filter that doesn’t leave gaps between the filter and its housing. Adding a non-pleated filter in your ductwork, attached with metal braces, can reduce the noise as well.
Clean the Ductwork
Dust and dirt can get trapped in your ductwork from many sources. When deposits build up, airflow is affected (and warm air can even become trapped), which can lead to banging and knocking sounds. Unless you are comfortable renting and using duct cleaning equipment, it’s best to hire a professional to thoroughly clean out your ductwork. Dirty fans can also make noise, so you can try to clean the HVAC fan as well.
Adjust or Upgrade the Dampers
Dampers help control the flow of air throughout your duct system. Sometimes a banging sound is caused by vent dampers that blow open and slam shut. You can fix the problem by adjusting the actuator in the damper, which can reduce or stop the noise. If your vent dampers are old, replace them with spring-loaded backdraft dampers that remain closed most of the time and open only when necessary.
Insulate Your Ductwork
If your ductwork isn’t properly insulated or doesn’t have insulation, add insulation to duct runs in the basement or attic. The insulation should be formed and designed to insulate ducts. The insulating material will muffle loud noises from within and it can improve energy efficiency as well. This can be a DIY project or you can have a professional insulate and line your ducts to ensure they are as efficient as possible.
Check Your Furnace
If a banging noise occurs when your furnace starts, the burners may be dirty. Carbon can accumulate on them as part of the combustion process. If the burners are coated, delayed ignition can occur. A large volume of gas ignites in the combustion chamber and causes a loud banging noise. This problem can damage the heat exchanger and possibly cause a fire, so call a technician immediately to perform furnace repair.
Change the Blower
An air conditioning and heating system with a single-speed blower is more prone to ductwork noise. It will only turn on and off. But upgrading to a variable-speed blower allows it to run at high speed and then adjust if a less significant temperature change is needed. It will use less energy and run much quieter. Overheating or overcooling can be prevented as well, reducing noise overall.
Install Ducts with an Insulated Liner
Insulated duct materials provide noise control and can improve temperature control, reduce condensation, and conserve energy. Sheet metal ducts can be lined with fiberglass insulation, while flexible ducts can be purchased pre-insulated. Both can function for years without any issues with moisture or mold, although porous insulation material must be replaced should microbial growth occur.
Consult a Professional to Stop Your Ductwork from Banging
Banging ductwork isn’t always a sign of something serious. But if you tried the tips above and/or don’t know the cause of the noise, it’s best to call a technician. At Sky Heating & Air Conditioning, we provide ductwork sealing, repair, and replacement services. If you need to ask, “how do I stop my ductwork from banging?”, schedule an appointment with us online or call 503-673-9083. We can be reached 24/7.