Author Topic: Vibrations from rooftop HVAC  (Read 10656 times)

seaspeas

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Vibrations from rooftop HVAC
« on: August 12, 2012, 09:21:23 PM »
We just moved into a top floor apartment, but we soon discovered that there's a very loud HVAC unit directly above us on the rooftop. We alerted the management, who looked into it for a few days, but they came back and said it was functioning properly and the noise was unfortunately part of the "consistent air filtration system" for our floor level. I walked up to the roof top and stood next to the unit in question (it's a large one; the maintenance guy told me it's like 50 tons -- though I know nothing about HVACs). It's indeed loud, but they do have a concrete wall surrounding it. It puts out a very inconsistent hum and vibration though, which is really the problem. I walked over to the other one on the other side of the roof, and it put out a more consistent hum. Neither was necessarily louder than the other, but the one above us definitely had an intermittent nature to its loudest times -- which of course hits our apartment like a neighbor whose sub woofer is too loud.

The only catch is that our furniture has not arrived yet, so we're living in a mostly empty apartment. Air mattress, few boxes and bags here and there, and a lot of open space. I've read that adding furniture and wall hangings will dampen noise, but since it's coming from the roof (and it's a vibration/deep humming sound), I'm not sure if having the couch and chair, full bed and mattress, etc., will do anything. If the noise is coming from above us, and we're not putting anything between us and the ceiling, we won't be reducing the noise, right? Or am I totally misunderstanding how this all works?

We've thought about relocating to another unit in the building, but we really like this particular apartment, and truth be told, if adding furniture and pictures to the walls is known to reduce this kind of noise, then we might just see how that plays out. But if it doesn't, we don't want to move all of our things in here and then have to move them to another unit; would rather just move everything into the new place and not fuss with it.

Just looking for some options in case the management doesn't want to do anything more about it (we have a meeting with them tomorrow, after an outside HVAC specialist looks at it). We don't have the ability to rip up walls or create new ceilings or any other sort of construction work relating to the drywall, windows, etc., that so many people suggest altering in this situation. Any advice that you can provide regarding ways to add things to one's apartment to reduce this kind of noise would be greatly appreciated, and thanks so much for your time.

--Steve

johnbergstromslc

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Re: Vibrations from rooftop HVAC
« Reply #1 on: August 12, 2012, 09:39:36 PM »
You are right - filling the apartment up with soft, absorbent stuff like furniture, drapes, etc will help.  If not, you do have the option of moving - you are lucky in that regard, most people are stuck...

By the way, the a/c unit that's 50 tons - that's not it's weight (if it were that heavy the vibration would be negligible), it's a measure of cooling capacity.  One ton = 12,000 BTU/hr, the amount of heat required to melt a ton of ice, in one hour.  So a 50 ton unit is 600,000 BTU's/hour.  An a/c system for an average house is 3-5 tons.

seaspeas

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Re: Vibrations from rooftop HVAC
« Reply #2 on: August 12, 2012, 09:46:37 PM »
Thanks John. That's obviously what we're hoping, but we all hate moving, and if we know ahead of time that filling space in the apartment won't provide much relief, then we can just arrange to have our things delivered straight to another unit. No use moving everything in and then moving out immediately.

We have very high ceilings (probably 15-16 feet), and our living area is a wood floor (bedrooms are carpeted). Already bought an area rug and will probably get more once our furniture arrives.

Just haven't seen anything quite like this in any forum -- that is, nothing where the person asking about the noise couldn't alter the ceiling or walls with new drywall, etc. Have been researching noise suppression items (i.e. heavy drapes, sound muffling panels that can be decorated to look like art work, and other similar items), but since those would be hung on the walls and not the ceiling, I wasn't sure if they'd provide any relief, given the source is above us, not next to us.

johnbergstromslc

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Re: Vibrations from rooftop HVAC
« Reply #3 on: August 13, 2012, 11:45:30 PM »
That sounds like a pretty sweet space.  If the furnishings don't reduce the noise, you could always talk to your super/landlord and ask if he would try to remedy the problem.  I'm guessing most of the noise is structureborne, and you can do something about that.  You'll want to break the vibration paths from the unit to the roof with resilient material, i.e. rubber pads.

If a solution like that is not feasible, you might just have to outlast it.  Only a couple more months of summer and the thing will be turned off...

seaspeas

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Re: Vibrations from rooftop HVAC
« Reply #4 on: August 14, 2012, 07:35:55 PM »
Definitely a really nice place, but we did move in all of our things today. Little to no difference in the sound. Bedroom might be marginally better (amazing what a full mattress and box springs does instead of just a crummy air mattress), but no real change in the living room.

Waiting to hear what the HVAC specialist says about it. Met with him earlier and he alluded to having the option of adjusting some settings and changing out filters, but if he's done any of that today it hasn't made a difference unfortunately. We don't have anything hung on the walls; curious if that would do anything, though I don't want to go punching holes in the drywall to hang things if we're just going to be relocating.

Mary B

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Re: Vibrations from rooftop HVAC
« Reply #5 on: July 08, 2013, 12:33:54 AM »
Hello,
I am having a similar problem with my rental unit.  I live in Durham, NC.  When I first moved into my apartment, it was acceptable, but then when the weather became warmer, it became intolerable.  I am measuring 50-63 decibels in my apartment more than 95% of the time.  Durham county noise ordinance specifies no noises louder than 50 dB during the night.  Would the law apply to my situation?  Can I force my apartment management to fix the problem?  Do you have any references?
Thanks

jhbrandt

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Re: Vibrations from rooftop HVAC
« Reply #6 on: July 11, 2013, 07:13:25 AM »
Mary,

I recommend that you check with ordinances about the noise issue.

Where is the noise coming from? - The walls? Ceiling? or is it airborne floating in through open windows or doors?

If airborne, you'll need better seals on the doors/windows, but if it is Structure-borne, the apartment management will need to put the unit on isolators - springs or rubber.

Usually this sort of noise is low-frequency.. and that's why it has not be taken care of before. - Low frequency isolation is expensive.

Cheers,
John

 

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