Author Topic: Noisy boiler room  (Read 10954 times)

Christos spirotis

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Noisy boiler room
« on: March 29, 2006, 10:42:50 AM »
I have a noisy boiler room underneath my living room.

When the boiler starts working i have loud noises in my living
room and the adjacent bathroom.

What kind of soundproofing should i do in the boiler room
in order to reduce noise.

Thanks in advance,
Christos

johnbergstromslc

  • Guest
Re: Noisy boiler room
« Reply #1 on: March 30, 2006, 05:32:34 AM »
You could do the usual treatment: insulate the joist cavities, mount drywall on clips and resilent channels, seal up gaps and penetrations.  But I have a suspicion that won't do it.  The boiler is probably mounted on the basement slab and rigidly connected to the rest of the building.  It's probably vibrating the whole structure and mounting it on resilient pads or springs is the only way to really kill the noise for good.  

Christos Spirotis

  • Guest
Re: Noisy boiler room
« Reply #2 on: March 30, 2006, 03:27:32 PM »
Thanks for your reply.

Would you say that it is highly unlikely that
the sound is transfered airborne from the machine -> structure (walls) -> airbone?

And do you have any suggestions as to where to look for pads?

Thanks in advance
C. Spirotis


johnbergstromslc

  • Guest
Re: Noisy boiler room
« Reply #3 on: April 01, 2006, 01:25:49 AM »
Quote
Thanks for your reply.

Would you say that it is highly unlikely that
the sound is transfered airborne from the machine -> structure (walls) -> airbone?

And do you have any suggestions as to where to look for pads?

Thanks in advance
C. Spirotis





Impossible to say without knowing the setup, the spectrum of the sound (probably most energetic in the lower frequencies) and the construction deficiencies.  Assume both airborne and structure-borne sound is responsible.  Aim to correct both.

As for pads, you'll have to judge what to use, based on the weight of the boiler.  You might want to use a piece of thick rubber.  Just make sure it won't get too hot and burst into flames or anything.  And be careful you don't burst any pipes when you're lifting the thing up.

But I'd do the airborne part first.  Insulate all the cavities in the boiler room, mount all the drywall resiliently (2 layers) and do some good sealing.  See how much better that is.  Maybe you won't have to mess with mounting pads.

Another benefit from drywall is that you increase the fire rating in the basement.  If something unfortunate happens in the boiler space, you'll have more time to escape (and the fire department will have more time to extinguish the fire) before your house burns down...
 

Christos Spirotis

  • Guest
Re: Noisy boiler room
« Reply #4 on: April 01, 2006, 08:17:23 AM »
Just made some spectrum analysis of the noise
with my laptop.

I have a lot of 100 Hz in my bathroom.

And guess what, i have a lot of 100 Hz in the boiler
room too!!!!

So i need to aim for materials that do well with very low
frequencies. Any suggestions?

johnbergstromslc

  • Guest
Re: Noisy boiler room
« Reply #5 on: April 02, 2006, 12:22:47 AM »
My advice remains the same.  To cope effectively with noise (esp. low frequency noise) you need mass and decoupling.  The ideal would be a floating floor, a layer of concrete on top of a soft underlayment, but you probably won't want to go to that extreme.  

As I said before, you should hang drywall resiliently - on not just the boiler room ceiling but all the walls, too.  But not before insulating the cavities with fiberglass batts, to attenuate the mass-air-mass resonance.  Do a thorough and quality sealing job with a flexible sealant.  (I use RTV - it has 425% elongation and lasts forever, but a good quality silicone caulk will work too. )

If you use 2 layers of 5/8" drywall, that will give you some good mass (~5.5 lb/sq.ft.) but make sure the ceiling panels are not rubbing up against the walls or the walls resting on the floors.  Anywhere one plane intersects another or any discontinuity or penetration occurs, leave a 1/8" - 1/4" gap and seal that up too.  Also, you can put a bead of sealant in the drywall seams and tape the seams and edges up with foil tape before you mud and tape the drywall.  Not necessary, but it adds a redundant layer, and it only costs 5 cents/ft., or something like that.  Just be careful not to puncture it with your mudding knife...

Check out the SSP clips sold on this site.  I am a definite convert to them.  When used with standard hat channel, they perform much better than channel alone.  And more forgiving to install, too.  

By the way, did you record the dB of the noise around 100 Hz (or the a-weighted average)?   What was the difference between the boiler room and bathroom?

Christos Spirotis

  • Guest
Re: Noisy boiler room
« Reply #6 on: April 03, 2006, 12:20:02 PM »
What i did was record a .WAV file using the laptop's soundcard
once in the boiler room and once in the bathroom while the
boiler was working. The recordings were about 15 seconds long.

Then i ran an FFT on both files using a kaiser window.

The 100Hz component in the bathroom was 4 db lower than
the 100Hz component in the boiler. So i guess i have about
half the noise in the bathroom!!!

I also put my hands on the wall that the exhaust pipe goes
through and it REALLY vibrates a lot. I think that this is the
source of my problem.

The boiler is connected to a chimney by means of a metallic
pipe about 20 cm in diameter.

If its either contact of the metallic pipe with the wall/chimney or
the exhaust fumes that causes the vibrations then i guess i
need to find a way to improve the setup.



johnbergstromslc

  • Guest
Re: Noisy boiler room
« Reply #7 on: April 04, 2006, 03:18:31 AM »
Christos:

If you have determined that the wall is vibrating - far more than could be attributed to any airborne noise - then, by all means, try to isolate and correct that aspect first.  Then, if the problem persists, do the construction.  Maybe you'll get lucky and not have to spend a lot of money.