Author Topic: ceiling insulation  (Read 5105 times)

fred

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ceiling insulation
« on: March 10, 2006, 04:58:50 PM »
does anyone know what level of sound dampening blowin-in insulation will provide on my ceilings?  i have loud upstairs neighbors and it is mostly their footfall that bugs me.  i can't invest in suspended ceilings or anything like that.  but part of the offensiveness of the sound is its reverberation, i think because our ceiling cavity is totally empty.  i am thinking about stuffing it with the hope that it may dampen or "distance" the thudding a bit and make it less intrusive.  any advice is greatly appreciated.  thank you.

johnbergstromslc

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Re: ceiling insulation
« Reply #1 on: March 13, 2006, 11:57:58 PM »
Cellulose will provide about 6 dB of attenuation of their airborne sound, but do nothing about the footfall noise.  That vibration will travel through the floor joists and right into your ceiling drywall.  In fact, if you eliminate the airborne noise (talking, music, tv, etc.) the thud from walking will seem even more annoying.  You have to mount the drywall resiliently to dampen footfall noise.

fred

  • Guest
Re: ceiling insulation
« Reply #2 on: March 20, 2006, 02:38:42 PM »
i can't expect any benefit at all for impact sounds?  my biggest issue isn't the "thudding" as much as it is the reverberation.  i was told that densely filling the ceiling cavity would help address this.  but i really don't want to spend the $ if it won't have any effect.  please help - thanks!!!

johnbergstromslc

  • Guest
Re: ceiling insulation
« Reply #3 on: March 21, 2006, 02:39:32 AM »
Fred:

Unlikely that any kind of joist cavity insulation will make any difference in impact noise.  As long as your ceiling is attached rigidly to his floor joists, the vibration travels efficiently through the solid material and radiates right down into your space.  If possible, you should both insulate the cavities (use fiberglass, though - easier to install upside down) and mount the ceiling drywall resiliently, but if it's and either/or situation budget-wise, forget the insulation.
And depending how much peace and quiet you like, you might have to do the walls, too.  The vibration will travel along the joists and into your studs (albeit with more attenuation and less noise than from your ceiling) and vibrate the drywall on your walls, too.  You could put on a second layer, where possible, maybe with some Green Glue (audioalloy.com) and that would help kill some noise.

fred

  • Guest
Re: ceiling insulation
« Reply #4 on: March 21, 2006, 03:27:32 PM »
thanks, john.

after doing some more research, i am going to insulate the cavity and apply an additional 2 layers of drywall to the ceilings with the green glue product.  i hope this will sufficiently dampen the footfall sound.  if it doesn't, i will look into doing the walls as well.   short of that i'll sell my place and make this somebody else's problem to fix.  thanks so much for the input.  i'll post results when the job is complete.

johnbergstromslc

  • Guest
Re: ceiling insulation
« Reply #5 on: March 22, 2006, 05:05:33 AM »
Glad I could help, Fred.

Yeah, that's about the best you're gonna do, unless you want to give up 8+ inches of ceiling height and construct a 'false' ceiling with joists separate from theirs.  But that is a lot more work.  

I tried to find some data as to how much improvement you could expect in IIC (impact insulation class, the rating used to measure structure-borne noise, including footfall noise) but couldn't really find any.  I'm assuming the upstairs neighbors have wood/tile/vinyl flooring.  A 'bare' floor/ceiling (plywood on wood joists with drywall attached) has an IIC of 37.  Adding insulation and resilient channels with one layer of drywall to your side kicks it up to 43.  But since you're adding two layers of thicker drywall, plus Green Glue, you could probably expect a rating of 50, maybe more.  This will seem 60% quieter.

The real trick would be to convince your neighbors to install carpeting.  Carpet with a nice, thick pad along with the modifications you're going to do would increase the IIC to almost 80 dB - a 95% reduction in the annoying 'thump, thump'!!  Hello, peace and quiet!

It is amazing how much difference a foam underlayment makes in impact noise.  The source I'm using also gives data for concrete slabs.  A 6" slab (massive enough that you'd think there'd be no problems) has an IIC of only 25.  Add carpet and pad and the IIC jumps to 86 - a 98.5% reduction.  

Also, I forgot to mention:  the best resilient system to use on the ceiling is SSP clips + hat channels (the clips are sold on this site and the hat channels at Home Depot or Lowes).  They are more forgiving to install than using the channel alone, and give better sound isolation.  Cost for both is about $1 per sq. ft. of ceiling, give or take.

 

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