First off, a furnace’s noise level is measured in “decibels”. So the short answer here is that the quietest furnace is the one with the lowest decibel (dB) levels.
The good news? You can easily find furnaces with dB levels as low as 50—which is roughly equivalent to the sound of a quiet conversation at home. For more context on dB levels, check out our chart below.
For context, here is a chart that breaks down decibel levels to common noise levels:
|Quiet conversation at home||50|
|Quiet, rural area||30|
The bad news? Most furnace manufacturers don’t make decibel levels readily available information.
But don’t worry—there are other factors to consider that affect a furnace’s noise level (and that point you in the direction of a quieter furnace).
Let’s explore the 3 factors that affect furnace noise levels…
Factor #1: High AFUE rating
“AFUE” ratings (Annual Fuel Utilization Efficiency) are used to measure the efficiency of a furnace—the higher the AFUE rating, the more efficient the furnace.
So how does that correlate to noise?
Well, typically, higher AFUE ratings correlate with lower decibel levels (i.e. quieter operation). That’s because, more efficient furnaces have more advanced motors and components that operate smoothly, quietly and at lower “speeds” (which brings us to our next factor).
Factor #2: Speed of operation (“stages”)
Another factor to consider when looking for a quiet furnace is how many operation speeds the furnace has. The bottom line is that furnaces that can run at lower speeds have lower operating noise levels.
Basically, there are 3 types of furnaces:
- Single-stage furnaces are the loudest because they can only run at 100% capacity.
- Two-stage furnaces are quieter than single-stage furnaces because they can fire at two different levels (low capacity and high capacity). When the furnace runs at the lower setting, decibel levels are much lower.
- Variable speed or modulating speed furnaces are the quietest because they can operate at unlimited speeds. Basically, variable-speed units can ramp up or down in speed depending on the level of heating needed. These units are designed to have much longer run times at much lower speeds so they’re typically always very quiet.
Factor #3: Faulty duct system
Unfortunately, even the most efficient, variable-speed furnace will produce loud noises if your duct work needs modification.
You see, duct work can cause loud popping noises due to air flowing through them. Sometimes, there’s no actual problem to fix here. Changes in air pressure simply causes metal duct work to expand and contract—which is the cause of the popping noises.
However, your tech can try making adjustments to your duct work to keep furnace noise levels.
To keep furnace noise levels under control, a tech can:
- Upgrade thin, cheaper sheet metal to thicker, commercial-grade duct work
- Replace square duct work with round duct work
- Improve the design of the duct work to incorporate less bends and turns
- Add insulation around the ducts
Need help choosing a quiet furnace? Ask a Kansas City tech.
We’ll go over all the options and help you find the best fit.