It’s the middle of the night, and suddenly you hear banging or popping coming from the ceiling or walls. Before you run screaming from the house, take a moment and remember that what you’re hearing is very likely duct and furnace noise. It’s probably quite safe and just means your furnace is doing its job.
Why Do Ducts Make a Racket?
It’s simple air pressure that makes ducts expand when a furnace or A/C is operating. As air rushes through the ducts, the increased air pressure forces the thin duct walls outward. Heated air may contribute to that expansion more than cooled air.
Surprisingly, this expansion effect may be more pronounced after you’ve had a professional duct cleaning. Removing dirt and debris that’s collected in ducts over a period of years allows the air to speed through the ducts with greater force, resulting in louder pops and bangs.
The shape of ductwork also has an effect. If your home’s ducts are square, they’re more prone to making a racket, since a square shape is physically weaker than a round shape, allowing expansion to occur more readily. Rectangular ducts are weaker still.
Thankfully, in most cases, the popping or banging related to ductwork expansion is nothing to worry about. It signals that the forced-air heating or cooling system is working as intended. Another duct or furnace noise – the whistling coming from vents during furnace or A/C operation – is also a positive sign that your HVAC system is operating properly.
As for specific furnace noises, beware if you hear a louder popping noise, or what sounds like a small boom, coming from the furnace. It could mean that the furnace burners are blocked by debris or rust and aren’t igniting immediately. As the gas accumulates, it will finally ignite with a small explosion. Contact a trusted HVAC technician to address this issue and don’t forget to schedule annual furnace maintenance.
To further discuss duct and furnace noise, or for other heating and cooling concerns, contact Bill Joplin’s Air Conditioning & Heating. We’re proud to serve Allen, Frisco, McKinney and nearby communities.
