Soundproofing a large closet with HVAC inside.

[frule]

Thanks,

I'll check it out........another question for the HVAC guy!

[daddo]

We had been in our home about fifteen years when the AC died.  When we replaced the AC they had to tear out portions of the duct work in the Furnace closet to install some of the control works for the new AC unit and we asked if it wouldn't be wise to replace the Furnace at the same time.  (We had asked this same question of all the bidders on the job.)  They all said that the furnace could last another ten years, or go next year.  Since labor was a large portion of the job, we decided to go with replacing it at the same time, and went with the OEM unit.  BIG mistake.  We saved about 30% over the next bid, but.....  (Replacing the 15 year old unit wasn't a mistake, the new unit was more efficient and saved propane in the long run... but)

When they fired up the new unit it sounded like a 747 taking off.  I called the owner of the company and he sent his "boys" back out.  They made some "adjustments" and it was certainly quieter.  Funny, but it was no longer cooling.  (Seems they overrode the system and prevented the three speed fan from going into HIGH.)  They came BACK out and reset the system to run at all three speeds and told me that they could order another FAN... at about $400.  The savings on the OEM system was accomplished in a variety of ways, but one way was to use a CHEAP blower motor / fan assembly.  The assembly has cheap bearings and very few of them and rumbles when it turns.  The fan blades are not the best in the market and are themselves noisy.  The motor and fan blades vibrate and that is transmitted through the metal closet it's mounted in and thru the duct work.  If you replace the fan, it will make a huge difference.  They put some silver insulation on the duct work behind the motor and it made a small difference, but they re-emphasized,  if you really want to lower the decibel level, upgrade to a high end blower/fan assembly.

We haven't done it yet, just haven't gotten around to it.  Really need to.  When the heat/ac cuts in, you have to turn the TV up loud.  When it cuts out, you have to turn it back down.  You watch tv with a remote in your hand.

Ask your HVAC guy if you have a low end assembly in your unit.  Perhaps replacing that will make a big difference and you won't have to insulate?

I can tell you that before we replaced the old system, we never had this issue. 

 Room permitting, one can line the inside of the blower compartment with 1" ductboard as well as the return air space under the furnace. An old technique that works quite well.  Then it may sound more like a Cessna 175.

[brianwelch]

Have you considered Quiet Rock drywall boards. Never actually used it, but supposed to provide the equivalent noise reduction of several layers of conventional GWB(and is available in fire rated...)
https://www.quietrock.com/products
Not cheap, but may be worthwhile...

[Cooler]

I visited a customer this morning and he has a noisy machine in a small room which he built from 2 x 4 studs and sheathed inside and out with homasote.

He used standard Homasote and the machine was virtually silent in the room.  They make a special sound deadening homasote that is even more effective.  I was impressed.

http://www.homasote.com/products/440-soundbarrier

[Robert Adams]

I visited a customer this morning and he has a noisy machine in a small room which he built from 2 x 4 studs and sheathed inside and out with homasote.

He used standard Homasote and the machine was virtually silent in the room.  They make a special sound deadening homasote that is even more effective.  I was impressed.

http://www.homasote.com/products/440-soundbarrier

Homasote is handy stuff but unless you have a Menards it's cost prohibitive. It's around $150 a sheet here and only by special order from the plywood supplier.

[Cooler]

Homasote is handy stuff but unless you have a Menards it's cost prohibitive. It's around $150 a sheet here and only by special order from the plywood supplier.

I had no idea.  It used to be the cheapest sheet goods that you could buy. 

In the early 1970s it was legal to sheath a house with homasote. So they had aluminum siding + homasote + fiberglass insulation + sheetrock.  I would guess you could shoot an arrow at the side of the house and possibly penetrate the wall and exit the opposite wall.

On the bottom left corner of each wall they used on sheet of plywood to keep the structure from racking.  I don't now why that system was abandoned (but I'm glad I don't live in a house built that way).  But clearly it was done to reduce cost so at one point homosote was cheaper than any other sheathing material.

[daddo]

Menards has homosote for 24 bucks.

1/2" x 4' x 8'.


I don't see a fire rating, but I'd guess it should be contained.

[Robert Adams]

Menards has homosote for 24 bucks.

1/2" x 4' x 8'.


I don't see a fire rating, but I'd guess it should be contained.

Yup and every time I'm doing a job up north I shop menards and at home I cuss that we don't have them because they carry all the odd stuff that I need. They even carry nice 4x8 sheets of plastic that is great for workbench tops.

         Took loml into one for te first time and showed her all the stuff I either can't get or is cost prohibitive to order here. I can't even order gutters in the color I want here but menards has them in stock...  Not to mention much cheaper than plain white at despot or blowes.

[EricU]

I'm guessing the OP's closet doesn't have any insulation, so the sound deadening Roxul stuff that they sell around here at the big box stores in combination with 2 layers of sheetrock would probably do a lot.  With a closet, putting one of the 2 layers of sheetrock on resilient channels might help a lot, and would be more space-efficient and easier than double 2x4's. They used to sell it at HD, but they don't any more.  I thought about using metal studs instead.

  As others have said, the door is also something that needs to be addressed. Wouldn't hurt to have a sound absorptive wall treatment, not sure what you use for fire resistance.  More than one club has gone up in flames because someone used a sound absorptive material that promoted fires.

[TDKPE]

With a closet, putting one of the 2 layers of sheetrock on resilient channels might help a lot, and would be more space-efficient and easier than double 2x4's. They used to sell it at HD, but they don't any more. 

I got mine at the local drywall supplier.  Paid for them, went out to the yard, and loaded them myself.  Only a few bucks a stick, but that was ten years ago.  The BORG only had other types of channel, but not the cantilevered sound-isolating resilient channel used for soundproofing.