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Recessed Lights Incompatible with Soundproofing?

Recessed Lights Incompatible with Soundproofing?

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  #1  
Old 02-06-07, 09:53 AM
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Recessed Lights Incompatible with Soundproofing?

A cautionary tale...

I have a two story house in which I'm just completing a remodel of the first floor. Because of the low (7'9") ceilings downstairs I decided to go with 4" insulation compatible recessed lighting units. Since I'm also planning on renting out the downstairs area, I was concerned about soundproofing so I went to some trouble to add lots of insulation in the ceiling joist bays. I also read great things about Green Glue, so I drywalled the ceiling with two layers of 5/8" drywall, with Green Glue sandwiched in between. It cost me a few $k more, but everything I've read online led me to believe that this would reduce the sounds from downstairs to a barely audible level.

Not so!

With the ceiling downstairs now complete, I can hear virtually every sound from downstairs on the second floor. It's all a bit depressing...

So on reflection, I think the culprit is those recessed lighting cans. They punch a series of nice 4" holes right through my Green Glued ceiling. In addition, the I/C cans are bulky enough that there's not much insulation on top of them (if any). So there's a nice sound path through the light fitting right up to the second floor.

Anyway, not sure what I can do at this point. If I could turn back the clock I would probably install track lighting instead, and make sure there was plenty of insulation on top of the ceiling boxes, but that's not really feasible for now. I can try to make sure that all the recessed cans are well sealed around the edges, but the cans themselves are unlikely to be very soundproof. Anybody else got any ideas or thoughts?

Damn!
 
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  #2  
Old 02-06-07, 10:08 AM
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Yup every single hole will compromise any sound insulation. In our studio, all electrical is surface-mounted and each wall penetration (wires, etc.) is sealed with acoustic caulk. If soundproofing is your goal, surface mounting everything is your best bet.
 
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Old 01-25-09, 07:24 PM
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Use of Air tight cans and RC?

Did you use air tight cans or Resilient Channel? I'm looking for advice on soundproofing floors and am wondering if can lights will really be any worse than surface mounted lights with 12" joists, R-19 insullation, and air tight, I/C contact cans, along with using RC-1 or using PAC RSIC-1?

Thanks in advance for any advice.

Justin
 
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Old 01-25-09, 07:48 PM
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I used air tight IC cans - no resilient channel (I have low ceilings and was worried about losing headroom).

In retrospect I would have skipped the green glue, used a single layer of 5/8" drywall together with resilient channel and sound clips, and minimized the number of penetrations through the drywall (with surface mount and track lighting).

The trouble with the cans is that even if they're airtight, they're still basically big hollow sounding boxes that break the insulation layer and block very little sound themselves.

One other comment - the double layer of 5/8" drywall makes a lot of fittings difficult to install which are sized for single 5/8". With resilient channel you'd have similar problems so you might want to focus on using old work boxes that don't have to attach to joists - this might also help reduce sound conduction.

In the end, I ended up pouring a 1.5" think gypcrete layer on top of the upstairs floor (with radiant heat pipes embedded), which has done a pretty good job of eliminating airborne noise between the floors (it adds about 11 pounds per square foot of mass), though, there's still an issue with impact noise transferred from upstairs to downstairs, which I think the resilient channel might have helped with.

Hope you have better luck with your setup!

Cheers,

Simon
 
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