Will a new furnace be quiter then a 30 year old furnace?
November 15, 2018 10:11 AM   Subscribe

Will a new furnace be quiter then a 30 year old furnace?

I'm looking at replacing our hvac both inside furnace and the outside system. Our current system is roughly 30 years old. It's loud. I do recordings in a near by room to the furnace. The room is treated for sound proofing but with our current system I can still hear it a little bit when the ac or heat is on. My AC guy says a new system with an ECM torque motor should be 20-30 % quiter running both ac or heat. The brand of the new one is Rheem. Do you think it will be noticeably quieter then what I currently have? Thank you.
posted by ljs30 to Home & Garden (15 answers total)
Anecdotally my family noticed a remarkable difference in sound switching from a 25 yr old oil furnace to a natural gas furnace. I suspect a lot of it will depend on what you have now, fuel sources available and how well insulated your home is.
posted by larthegreat at 10:22 AM on November 15, 2018 [1 favorite]

What are you actually hearing? The low cycle hum of the fan motor? Rushing air noise?

If you are hearing anything duct-related (not electrical), consider having the ductwork re-braced to the structure, and if you're getting the low cymbal-crash of ductwork as it moves to different pressures, you can have it braced with just some strut on the long axes.
posted by notsnot at 10:31 AM on November 15, 2018 [1 favorite]

Response by poster: I am hearing the sound of the furnace motor running. It's basically as loud as a window ac unit if that makes sense.
posted by ljs30 at 10:35 AM on November 15, 2018

I just got my natural gas furnace replaced. Mine was only about 20 years old, but the new furnace is about 3/4 the size of the old furnace. This means the blower motor is also much smaller and quieter, but I can still hear it.
posted by The_Vegetables at 10:45 AM on November 15, 2018

My parents replaced theirs a couple years ago and my mom remarked that it was tiny and silent in comparison.
posted by restless_nomad at 10:53 AM on November 15, 2018

Yes. I had an old forced air furnace replaced a few years ago and the noise went from rocket ship launching, turn the tv up as far as it can to go to hear it to I don't turn the tv up at all and can hear the tv even at low levels while the furnace is running. It's way more efficient as well.
posted by BooneTheCowboyToy at 11:03 AM on November 15, 2018

You could replace it with a two-stage furnace. Most of the time the furnace burners and blower run at low speed to maintain an even temperature. It only goes to high speed for large temperature changes. The newer blower motors are electronically controlled so they have a wide range of speeds. You are less likely to hear them start and stop.

When shopping specify a two-stage furnace that allows some user programming so you can tune it to the response you want.
posted by JackFlash at 11:04 AM on November 15, 2018 [1 favorite]

Chances are your old furnace motor hasn't been lubricated for awhile (it's not really in the interests of your AC guy to suggest this). I would do that first, but the new furnace will probably be quieter regardless, though the new furnace will probably shift the peak remaining noise to a higher frequency than the old peak noise.
posted by jamjam at 11:09 AM on November 15, 2018

I was expecting mine to be more quiet, but it actually ended up being louder. Not sure if I didn't shop well or what, but YMMV.
posted by willnot at 11:23 AM on November 15, 2018

You could replace it with a two-stage furnace.

My two-stage is certainly quieter in terms of the actual motor starting and running. In terms of the air going through the ducts, that's probably the same. However, with a two-stage, the furnace goes more often but for much shorter times, making it less noticeable overall.

As a data point, my new gas furnace replaced a 15 yr old oil furnace. ("High-Efficiency Oil", they called it, which is Not A Thing.)
posted by Capt. Renault at 11:51 AM on November 15, 2018

Generally speaking, properly sized units will be quieter than the 30-year-old units. However, a big caveat to that is the structure and layout of the home itself. For instance, if it’s a small place and the hvac is in a closet next to the bedroom, you’re going to hear it. There’s just no way to avoid it.

Now, if the new stuff goes in a basement, it’s possible you’ll never know it’s there.
posted by Thorzdad at 3:38 PM on November 15, 2018

There's two big sources of noise. The motor of the furnace fan itself, and the airflow. Replacing the furnace will almost definitely quiet noise for the motor; any new motor is going to be better and also running much smoother by virtue of being not worn down.

Duct / air noise is harder to manage. But a two stage system should help, if it mostly runs on the low setting. I have a fancy variable-speed / multi-stage HVAC system and it is definitely significantly quieter. It runs more often but at like 1/5 or 1/10 the air volume, so you don't hear the air moving.
posted by Nelson at 4:59 PM on November 15, 2018

I replaced a 14-year-old forced air furnace with a new one and it’s so much more quiet. I barely notice when it comes on.
posted by bighappyhairydog at 7:51 PM on November 15, 2018

We replaced a 30-year-old forced-air furnace with an equivalent (probably nicer) one, and it got louder. That was due to efficiency reasons, because the new furnace pushes more air to exchange more heat/cold. However, you can turn down the fan speed at the cost of reduced efficiency. The actual noise of the furnace operating didn't change.
posted by wnissen at 9:15 AM on November 16, 2018

Obvious question, how often have you had your system serviced? How recently?
posted by ivan ivanych samovar at 1:38 PM on November 16, 2018

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