Noisy Metal Ducts

Metal ducts may expand and contract as the temperatures change.

The metal duct work in your house transports heated or cooled air, keeping the inside temperature comfortable. Sometimes the ducts may make popping, ticking or other noises that can be annoying. Investigating the cause of the noises can be time consuming, but you may at least reduce the noises in the end.

Expansion and Contraction

The metal ducts in your house may expand and contract at different times, depending on how you are using them. Since the ducts are made of metal, they may expand a bit each time the furnace kicks on. When you run the air conditioning, the metal ducts may contract from the exposure to cold air. The sounds you hear may be caused in part by the ducts expansion and contraction, especially if the noises start right after the furnace or air conditioning first turn on.

House Frame

The expansion and contraction of the metal duct work makes the ducts move and come into contact with the framing in the house, creating even more noise. When an installer puts in your house’s ducts, he should take into account the potential expansion of the ducts and place sufficient space between the ducts and your house’s framing. Placing a duct right next to the framing will result in contact between the two.

Locating the Source

Finding the exact source or what part of the duct work in your house is creating the noise requires a certain amount of detective work. You may have to cut into your house’s walls or ceilings, unless you are lucky enough to have an unfinished basement with the ducts exposed. As you chase down the noise through the walls or ceilings, look for ducts that touch the wood framing in your house.

Fixing the Noise

Once you find the source of the noise, you can exercise a number of options for a resolution. Some fixes may give you a partial relief from the noise, while others completely eliminate noise. You may place rubber pads between the ducts and the framing at the point of contact. A home inspection service can come to your house and examine the contact point, and then advise if you can cut away any of the framing without compromising your home's structural integrity. You may also bring in an HVAC system specialist who can analyze the ducts to ensure they are not overloaded.

References

• Ask the Builder: Duct Noise
• This Old House: How Do I Quiet Noisy Ducts?