News & FAQ

Duct, Duct, Ghost: Strange Sounds in the Duct Work

10/30/2014

Valerie Johannsen People & Brand Manager

It’s the night before Halloween and your senses are heightened to all the strange noises around you. In particular, you are noticing strange sounds coming from your heating system and ductwork, like bangs, whistles, and pops. “Is this normal,” you think, “or are there ghosts in my ducts?”

If you hear a lot of loud, unfamiliar sounds coming from your HVAC system, that could be a strong indicator that something is wrong and needs to be fixed. Pops, bangs, and whistles coming from the expansion and contraction of your metal air ducts, however, is considered quite normal.

Especially in older homes with all-metal ductwork, the expansion and contraction of the ducts create lots of different noises. The “tinning” or popping sound is caused by temperature changes and heightened air pressure inside of the ducts when the blower turns on.

The expansion and contraction of the ductwork create audible popping and banging sounds that may lead you to think your house is filled with ghosts, but in fact, these popping noises are harmless and there are ways to reduce the amount of noise.

If you hear really loud banging and popping, you may want to call a Service Legends professional to diagnose the problem as it could pose a safety hazard.

Reduce the noise

Let’s examine the different ways that your furnace and ductwork can make strange sounds and what you can do to help reduce the noise.

  • Ducts have different shapes and each shape can withstand different degrees of pressure: round ducts are able to handle the most pressure, followed by square ducts, and finally, rectangular ducts, which can take the least amount of pressure. Although it may be too expensive or impractical, consider having a duct system shape change or switching to a high-pressure or high-velocity duct system. You can also insert duct liners, or cover all your ducts with fiberglass insulation. If the ducts are expanding and hitting its wood frame, consider putting rubber padding in between the metal and the wood to create a barrier.
  • Make sure all of your air vents are open and nothing is blocking the registers or the returns. It is a common mistake to close air vents in unused rooms. This increases the pressure within your ductwork, creating more noise and decreasing your system’s energy efficiency.
  • You may want to take a look at your furnace filter and check to see if there is an airflow restriction problem.
  • Have your Service Legends technician check to see if your HVAC system is blowing too much air into your ductwork. Ask our technician to also check to see if you have a flexible furnace transition from the furnace to the ductwork.
  • Leaks in the air ducts can create a whistling sound when there is high-pressure air escaping from the cracks in the ductwork. Ironically, duct tape is not a good tool to use for sealing air ducts; instead, use “foil tape” and silicone or mastic caulk sealant.
  • You can see if your air duct is dirty by taking a picture. Simply, unscrew your vent/register plates and stick a flash camera deep in there. If it looks anything like the left picture, call Service Legends right away to make it look like the right one.

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  • And finally, if you want to get rid of loud and annoying noises from your HVAC, the best thing you can do is to schedule regular maintenance on your HVAC system. You may have a faulty blower, dirty coil, frozen up coil, or something else that needs to be serviced. In addition to finding any problems that are creating excessive noise, your Service Legends regular maintenance will also help you save money by creating a more energy-efficient HVAC system.

Heating and Cooling Des Moines Since 1997

At Service Legends, we take pride in heating and cooling Des Moines and the surrounding areas. Our HVAC services include furnace and air conditioner installation, repairs, maintenance, and tune-ups. Our lineup of Indoor Air Quality solutions includes whole-home humidifiers, air purifiers, and air filtration systems. We can even help with HVAC financing.

Call 515-657-6634 to contact our Home Comfort Heroes today. We’re standing by 24/7.

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