If you’ve installed a new HVAC system or recently had your ducts cleaned, you may be hearing some odd noises coming from the ducts in your home that you haven’t heard before. Most of the time, some popping in the ducts is completely normal and no cause for worry.
So, why do ducts pop? First, it’s important to remember that most air ducts are made of sheet metal, and when metal expands suddenly, it makes a popping noise. There are two main culprits that can make your air ducts expand—air pressure and heat. When your HVAC system cuts on, it blows air into the ducts. In a new, clean system, this air comes through at a high pressure, quickly filling the ducts and forcing them to expand. This is particularly true with rectangular ducts, which cannot withstand as much pressure as round or square ones.
Likewise, when the heat comes on and a whole lot of hot air fills up cold metal ducts, the heat from the air causes the metal to expand quickly. Again, this can lead to a harmless popping sound, especially if the ducts are in contact with wood structures that can reverberate and carry the noise.
If the popping is loud and frequent enough to be annoying, there’s a few things you can try. One is to have a licensed HVAC technician check to make sure that your system isn’t pushing too much pressure through the ducts. If the duct is in contact with wood, you can put a rubber pad in between to stop the reverberations. Making sure that the air intake is unblocked and replacing your filter regularly can also help to avoid problems with uneven pressure.
Ultimately, a little popping, especially in a new or freshly cleaned system, is generally no problem. It’s just the sound of metal expanding from the heat or pressure of the air rushing through it to warm up or cool down your home.