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Discussion Starter · #1 ·
Not necessarily theater related (although there are speakers involved), but definitely construction related...


I just found out that there is no insulation between my ground floor and second floor in my kitchen and family room. Ripping down the drywall and fully insulating is not an option because A) they're the most used rooms in the house and B) I have a complex grid laid out on the ceiling for construction of a coffered ceiling, and 75% of the nailing studs are already installed, so I'm not pulling all of that back down.


I saw a post by Ted White stating that beyond 50%, there's a diminishing return in filling the cavities. I'm wondering if I could use the fact that 6" fiberglass insulation rolls won't fill the cavity completely to allow me to push insulation in from a slot cut at one side of the ceiling, until no more insulation will go in? Or is this an application for blown-in insulation?


Thanks!
 

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No need to panic. Tests show only about a 3 point improvement in Sound Transmission Index with insulation vs. none.
 

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Agreed.


My comments regarding insulation were with decoupled framing. In a decoupled scenario the addition of mass and insulation has a much better payback.


In your coupled ceiling scenario the insulation isn't such a big deal. It will technically improve things, but many would say that the cost and effort relative to the gain makes it not worth doing.
 

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Depending on your upstairs you may be able to remove the subfloor and install it that way but I doubt you would want to do that.


Maybe if you removed the speakers and made boxes in the ceiling that would seal the sound off.
 

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Discussion Starter · #5 ·
Thanks all. I think I'll just build boxes for the speakers and insulate around the can lights I'm installing (where I have open access to the joist bays) and call it good.
 

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My HT is a retro-fit, and like many, if not most homes, I didn't have insulation in the interior walls and floor cavities. I didn't want to tear down the sheetrock off my ceiling of my HT so I had a company come in and cut small holes in each floor joist cavity and blow in insulation.


Insulation, especially blown-in insulation, doesn't do a whole lot, from what I hear, but they were already coming to my home to blow in insulation in the attic, so I just had them do the theater. Then I added another layer of GG + sheet rock to the theater ceiling and walls. I'm not finished yet, so I can't give you a full report, but hopefully this gives you an idea of what other folks do in your situation...


Now if you wanted to decouple your HT ceiling with isolation clips, then you have to tear off the existing sheetrock ceiling anyway, so you could add insulation.


You could also forget the can lights and in-ceiling speakers and go with wall sconce lights, and other in-room ways of mounting speakers...
 

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Do I understand this correctly? He would not get much sound isolation from ripping out ceiling/walls and installing insulation? A larger/cheaper gain would be had by decoupling?
 

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That's correct. It's still best to incorporate the all 4 basic elements of Decoupling, Absorption, Mass and Damping. All 4 perform separate functions and one does not replace the other.


Insulation, for example has a more important role in a decoupled system. It helps drop the LF resonance point. This distinctly helps with LF isolation, and is not reflected in STC measurements. So insulation is an important component in high performance isolation.
 

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Quote:
Originally Posted by Ted White /forum/post/18546857


That's correct. It's still best to incorporate the all 4 basic elements of Decoupling, Absorption, Mass and Damping. All 4 perform separate functions and one does not replace the other.


Insulation, for example has a more important role in a decoupled system. It helps drop the LF resonance point. This distinctly helps with LF isolation, and is not reflected in STC measurements. So insulation is an important component in high performance isolation.

Yes, Ted makes a good point here. The insulation filling the cavity effectively changes the speed of sound within it (vs. just air), and that lowers the resonant frequency a bit (by a factor of 2^-3, if I am remembering the equations correctly).


- Terry
 
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