Author Topic: Recessed lights unavoidable--any point to 2-layer drywall + GG?  (Read 311 times)

shayyadin

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Our 1923 Colonial has an insane amount of noise communication. My wife was talking to a plumber in the basement yesterday, and I could hear it in the bedroom two floors away.

I use that basement as an office, and we are in the middle of a renovation. I have been thinking about putting in rock wool insulation and then putting up a double layer of drywall with green glue in between. My understanding is that, as an elastomer, the green glue should attenuate some of the kinetic energy coming through the studs, whereas the rock wool should help to limit the communication of airborne noise.

Now, here's the problem: the ceiling is barely 7 feet, so we just can't do track lighting. We already have wall lighting and it isn't enough, because there's no natural light. Recessed lighting is simply unavoidable. We also have to cut out 1 sq foot for a plumbing access.

Given the fact that we will be putting a bunch of holes in the ceiling, is there any point to the extra cost associated with the double layer of drywall and the green glue? Or will all the sound just come through those openings, making noise attenuation a hopeless goal?

Randy S

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Re: Recessed lights unavoidable--any point to 2-layer drywall + GG?
« Reply #1 on: March 19, 2019, 03:03:40 PM »
Build boxes for each can light and caulk them. make the box the exact same assembly as the ceiling so if you are doing double drywall with green glue then the box is double drywall and green glue.
same with your plumbing access hatch.

Randy S.
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shayyadin

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Re: Recessed lights unavoidable--any point to 2-layer drywall + GG?
« Reply #2 on: March 19, 2019, 03:32:55 PM »
Hi Randy,

This project is already above our budget, so building boxes on top of everything else is just not going to be in the cards. Prefab QuietBoxes are $60 and would require customization and installation, so we're talking probably another $1200 or $1500, which we don't have. Having someone custom cut a bunch of drywall, put green glue between the layers, and caulk them together has to cost even more than that. Is the double layer of drywall with GG a waste of money without the boxes?

Thanks,
David

Randy S

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Re: Recessed lights unavoidable--any point to 2-layer drywall + GG?
« Reply #3 on: March 19, 2019, 03:46:16 PM »
if you do not build the boxes you will be at 2% - 5% leak and you could lose up to 60% of your potential performance of the ceiling system.

Randy S.
Randy Sieg

Super Soundproofing Co
www.soundproofing.org
888-942-7723
Ph. 760-752-3030
Fax.760-752-3040

shayyadin

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Re: Recessed lights unavoidable--any point to 2-layer drywall + GG?
« Reply #4 on: March 19, 2019, 03:52:18 PM »
Thanks, that helps. I'd like to try to get a better sense of what losing 60% means, or for that matter, how much performance I might have gotten in the ideal case. Right now, every footfall sounds like someone is hammering above me. (Like, REALLY loud--I think it's actually getting amplified somehow.) Every word someone says sounds like they're in the room with me. Let's say I put in 3" of rock wool, build the boxes, and put two layers of drywall with green glue. How do the footfalls and the voices sound now? Suppose that I lose 60% of that performance--how about now?

Randy S

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Re: Recessed lights unavoidable--any point to 2-layer drywall + GG?
« Reply #5 on: March 19, 2019, 04:02:23 PM »
that system will do very little for footfall....that is an airborne sound approach..
if you want to reduce impact/footfall noise you must decouple with resilient channel or clips and channel. 
or carpet and padding on the floor above..

Randy S.
Randy Sieg

Super Soundproofing Co
www.soundproofing.org
888-942-7723
Ph. 760-752-3030
Fax.760-752-3040

shayyadin

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Re: Recessed lights unavoidable--any point to 2-layer drywall + GG?
« Reply #6 on: March 19, 2019, 04:07:37 PM »
I was afraid of that. The problem is that I can't find any contractors who know how to do resilient channel in my area (Maplewood, NJ). Any advice?

Randy S

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Re: Recessed lights unavoidable--any point to 2-layer drywall + GG?
« Reply #7 on: March 19, 2019, 04:16:35 PM »
That surprises me since any multi residential build after 2006 is required to have them by international building code.
I would look for a drywall company that does multi residential projects.

Randy S.
Randy Sieg

Super Soundproofing Co
www.soundproofing.org
888-942-7723
Ph. 760-752-3030
Fax.760-752-3040