Why is My Furnace So Loud?

Now that you’re using your furnace full-time to keep your home warm and comfortable, you may have noticed a few odd sounds when the unit is running. Many sounds are normal and aren’t of concern – they don’t indicate a major problem. However, some sounds may indicate that all is not well within this vital home appliance.

As a homeowner, you can do some investigative work to try and figure out where the sound is coming from, as well as its cause. In fact, there are some odd furnace noises that can easily and quickly be taken care of by the average homeowner, perhaps by something as simple as changing a filter. More complex problems, however, such as a loud bang caused by a delayed ignition, are better left to the professionals.

Here are a few common furnace noises and their potential causes.


If the bottom of your furnace isn’t level with the floor’s surface, you may notice a rattling sound when the system is running. This is a problem with a simple solution – add rubber anti-vibration padding underneath the furnace. Your local hardware store will likely have these pads in stock.

Additionally, a vibrating sound when the furnace is running could indicate that you have loose ductwork. This isn’t a major cause for concern. A heating professional will be able to place additional screws into the ducts to keep them from rattling. If you feel confident in your ability to handle the task, you may be able to complete the work on your own. Along with adding extra screws to your ducts, you may also be able to fix the problem by adding electrical tape to secure loose areas.

Banging noise

When your furnace cycles on, do you hear a loud bang? This is often caused by a weak area of ductwork. Warm air from your furnace expands into your ducts when the unit is running. This extra pressure on a weakened area of the ducts could cause it to push outward and “pop,” hence the loud banging sound you hear when the system switches on. The problem can easily be taken care of by replacing this section of ductwork, or a professional may be able to add a special support device on the outside of the duct.

Alternatively, the banging noise may be caused by the ignition process that takes place when your natural gas furnace cycles on. To determine whether this is the cause of the loud noise you hear, stand by your furnace when it comes on. If you see the doors on your furnace shaking when the unit comes on, and you hear the noise, this is likely the cause of the sound. It’s nothing of concern as it’s something that often happens with natural gas systems.

One of the lesser-known causes of a banging sound when the furnace is running is when the ducts under your flooring are too tightly secured into place. You may notice a loud banging sound when you or another family member are walking across the floor in certain spots. A heating professional will be able to loosen the duct so that it isn’t so snuggly in place. It’s important for ducts to have some “give” to them, but they should also not be too loose.


Many times, a whistling sound that’s associated with a furnace is a result of a clogged air filter. When your furnace filter is full of dirt and dust, the system’s fan will try and pull in air wherever it can. Air will be pushed through tiny holes in the filter, and as a result, you may hear a distinct whistling noise.

It’s important for you to routinely change your air filter. If you aren’t sure how often it needs to be replaced, refer to your owner’s manual. It will tell you how often to change it, as well as what size you need. Keeping up with replacement filters is necessary to prevent jeopardizing your family’s indoor air quality, and to prevent premature wear and tear on your system.

In addition to a dirty air filter, a whistling noise when your furnace is running could indicate there is a hole where your ductwork connects to the furnace’s blower. A heating professional will be able to determine the exact location of the hole and get it fixed.

Motor sounds

If the bearings attached to your furnace’s motor are worn out and in need of replacement, you may notice that it makes a continuous sound when the system is running. A professional will be able to replace the bearings for you and resolve the issue.

Protect your family’s heating system

In addition to being mindful and proactive in taking care of any strange sounds you hear from your furnace, remember to keep up with routine maintenance. Schedule a heating tune-up with a skilled service technician to ensure your system runs efficiently all season long.