Troubleshooting a Noisy Forced Air Furnace

The forced air furnace system is the standard in home heating. In this type of system, hot air is forced through a spiderweb of duct work that runs throughout the home. It eventually passes through the vents to heat the entire room. Over time, the forced air furnace may begin to get noisy for several reasons. Read on to learn how to determine the cause of the noise and how to fix it.

Listen and Learn

When your forced air furnace is too loud, you may only need to take the time to listen to it to find the cause of the noise. If you hear clanging, the problem will most likely be the fan or the grates shifting. A quieter noise might be the duct work shifting.

Tighten the Screws

A forced air furnace has many components that must be screwed in place, including the fan, the grates and the duct work. As the air is forced through the system, it will cause metal to expand and then shrink once the hot air has stopped. This shifting coupled with the forced air can cause screws to eventually become loose. Go around the home with a screwdriver and tighten all of the screws located in the floor vents. Find the fan on the forced air furnace and tighten the fan as well as the grate.

Duct work is often connected with screws from section to section. Tighten these screws to keep that tight bond between the duct work sections.


Many builders will not take the time to insulation a forced air furnace or the system. There are two different ways you can insulate the forced air furnace. The first is to wrap the actual furnace in aluminum backed foam board. You want a kind that is fireproof, and you will need to cut it to fit as well as trimming out sections for pipe and duct. You attach the pieces with foil tape.

The other thing you can do is to insulate the duct work. The easiest thing you can do is to wrap the duct work with natural cotton insulation which will prevent sound from escaping. On top of the duct work you would wrap it with aluminum foil. This helps to keep the insulation in place but also stops heat from escaping the duct work.


There is usually no filter between the heat vent and the duct work which makes the duct work vulnerable to debris entering the duct work through the vents. Detach the duct work at the furnace and blow air through the vents. Any trapped debris will come out the duct.