# ceiling insulation



## flash (Feb 18, 2009)

What is the best route to go with insulation for the theater ceiling? I don't want to break the bank, but i want something that will reduce noise. Mineral wool is somewhat expensive, but if it's the best route then i guess i will do it. If i go with fiberglass what R value should i use? Paper faced or not?


----------



## bpape (Sep 14, 2006)

What 'noise' are you trying to stop? If it's just mid and high frequency and things coming INTO the theater, filling the cavity full of standard insulation will help a good bit. If you're trying to stop low frequencies, you need that plus additional mass - like another whole layer of drywall. You'll also need to pay attention to any openings for things like can lights, HVAC, etc.

Bryan


----------



## flash (Feb 18, 2009)

yes, mids and highs. The bass shakin' thing should be ok, because i really do not want to do a second layer of drywall. I have 5/8 going up and that's all I can handle. So what R value do you think I should use?


----------



## Space (Jul 18, 2007)

The R value has no bearing on your choice of insulation as a means to burn off frequency. What does is the depth of cavity or area you are trying to install it in. 

As a rule of thumb, my thumb anyway, whatever the depth is of the lumber, get the r-rated equivalent.

4" depth, get r 11.
6 inch depth, get r 19

The main thing is to not compress the insulation, too much.


----------



## bpape (Sep 14, 2006)

Correct. Fill the cavity full even if you have to (and you will) use multiple layers. There is no need to compress it - though it won't hurt anything much from an acoustical standpoint if you do. That'll only impact it's heat insulation properties which we really don't care about.

Bryan


----------



## Space (Jul 18, 2007)

The posters question/situation is un-clear to me as it is written. If the r value is under question then by way of simple error it should be noted that over-compression of this material can create a bridge and diminish isolation.


----------



## bpape (Sep 14, 2006)

I think people usually refer to R value as that's how it's sold rather than by thickness. You're correct that if it was severely compressed (like 3.5" down to 1") then there could be some transmission.

Bryan


----------



## flash (Feb 18, 2009)

My basement ceiling rafters are 12" should I use R38?


----------



## bpape (Sep 14, 2006)

Not sure what thickness that is but if it's close to 12" then yes.

Bryan


----------



## Space (Jul 18, 2007)

flash, As a sound reducer, insulation is often not thought of in this capacity. Not alone, anyway. As part of a system it is used to damp panels from vibration and stop high frequency. 

Maybe if you explained more about your situation you would get better clarity.

Bryan Pape is a noted professional in this field, he can help.


Mass is what stops sound, it has no equal. In whatever form you get it, mass is the way to beat sound from moving between panels in a wall or ceiling system.

Please share more if you have time.


Brien


----------



## bpape (Sep 14, 2006)

Absolutely - mass is always your friend. As has been said, the cavity still needs to be filled or we just get a drum that's tuned lower. 

Bryan


----------



## flash (Feb 18, 2009)

I bought r30 and r11 both stacked i believe gives me the 12 inches i need. The only problem is my joists are about 17.5 inches wide and the insulation is 15". Should i just cut and stuff some insulation in the 2 inch gap? I bought un:yay2:faced. I figured faced was not needed.


----------



## bpape (Sep 14, 2006)

Unfaced is just fine. You might be OK with out stuffing but if you have extra, I would.

Bryan


----------



## Ted White (May 4, 2009)

As a side note, while filling a 12" cavity you can use R38, but there are little benefits gained in STC and IIC beyond R19. Hard data, not opinion, there.

Also, it makes no difference where the insulation is placed withing the cavity. Up by the floor, down by the ceiling or in the middle. Again, all based on actual lab tests.


----------



## Ted White (May 4, 2009)

Space said:


> Mass is what stops sound, it has no equal. In whatever form you get it, mass is the way to beat sound from moving between panels in a wall or ceiling system.


Mass is one of 4 elements of soundproofing. I would not characterize it as having no equal. A system primarily dependent on mass will still resonate and conduct. In the real world, you'll never get enough mass to depend on it exclusively.

Rather, you would prefer to attack a sound containment system using multiple elements. Decoupling, mass, absorption and damping.


----------



## Space (Jul 18, 2007)

Good to see ya again Ted 

Space said:
"As part of a system it is used to damp panels from vibration and stop high frequency."

It's been covered, but thanks for watching out for me.

BTW, would you have access to the lab data you mention?


Good luck,

Brien


----------



## Ted White (May 4, 2009)

Hello Brien,

This comes up from time to time.

http://irc.nrc-cnrc.gc.ca/pubs/fulltext/ir766/ir766.pdf

Courtesy of the NRC in Canada











Note that there's not much performance gain after R19


----------



## Space (Jul 18, 2007)

The link you want is here:
http://irc.nrc-cnrc.gc.ca/pubs/ir/ir766/

The data will also show(top of actual page: 88) that there is a point difference in STC and/or IIC depending on placement of absorption material.  If points matter...

Thing is, this is a good document, maybe not for this specific topic as it was written based on data produced by many different assemblies of many different materials in many configurations. So a broad statement taken out of context cannot be made with this document as support.

Page 25 will disagree with you. A thickness of 90mm to 456mm(3 - 1/2" to 18") shows an increase in overall performance in both STC and IIC.

But it only applies to the 457mm depth wood I-beam with 15mm OSB attached on top, 610mm O.C. RC with 1 layer of 15.9 gypsum 

It also will prove my statements incorrect about "bridging" from over stuffing! Whadaya do?

I appreciate what your doing. I love this stuff too!

Brien


----------



## Ted White (May 4, 2009)

Thanks for that URL Correction... not sure what happened to the old link.



Space said:


> The link you want is here:
> http://irc.nrc-cnrc.gc.ca/pubs/ir/ir766/
> 
> The data will also show(top of actual page: 88) that there is a point difference in STC and/or IIC depending on placement of absorption material.  If points matter...
> ...


----------



## Ted White (May 4, 2009)

On a side note I like to talk in terms of "practical" improvements rather than "technical" improvements. 

Doubling up on a material to get a point of improvement may technically be better, but considering the cost, it is not practically better. 

Green Glue for instance is technically better at 3 tubes per sheet, but we never recommend more than 2 for the practicality.


----------



## bpape (Sep 14, 2006)

That was where we were with a couple of my customers. I told them that if they really wanted the extra isolation, they'd be better with 3 layers of drywall and 1.5-2 tubes per sheet rather than just 2 layers and 3 tubes. It's more work but it's serious isolation. 

Bryan


----------



## Ted White (May 4, 2009)

That is exactly right. More mass in the second scenario and damping is more effective in layers.


----------

