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Green Glue - Again!

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Green Glue - Again!

Postby The Byre » Sun Feb 19, 2006 12:36 pm

Did we ever receive an answer on Green Glue and how it compares with conventional glues?

I know that according to the manufacturer, after using this stuff, you should be able to walk on water, leap tall buildings at a single bound and it may bring us the answer to World Peace. But has anybody tested this stuff and compared it one-on-one with conventional glues?
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Re: Green Glue - Again!

Postby Eric Desart » Sun Feb 19, 2006 12:49 pm

The Byre,

While there certain are other formulas then Green Glue thinkable ( :blush: for experts, not for me). Green Glue is very specific designed to constrained layer damping.

Hence the comparison with conventional glues is almost a non-issue.

The damping values of Green Glue are noted on the Audio Alloye site. And they are about unique.
Hence, where increasing damping causes a gain, Green Glue is indeed a superior solution.

With standard glue you run as well and even likely the risk that you deflate the TL of the wall. It doesn't or hardly increases internal damping and just shifts the coincidence downwards, which in itself can be the cause of trouble.
;) Hence it's a bit like comparing a carr with a dish washer.

The question for Green Glue is how cost effective is it, and then compared to good standard walls without being glued.
The comparison with a standard wall on common wooden studs, is as comparing with a worst case situation for me, where the properties of Green Glue indeed will show at their best.

But within what Green Glue is designed for and how it works with CLD (constrained layer damping), comparison with conventional glue which is meant to glue is really no comparison at all.

Warm regards
Eric
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Re: Green Glue - Again!

Postby Rod Gervais » Sun Feb 19, 2006 6:15 pm

Byre,

I have to pretty much agree with Eric on this, you can't compare Gree Glue with standard adhesives because the job they do is very different. This material is not intended to glue in the sense that the 2 (or more) sheets become one - as is the case with standard adhesives.

In that case you may as well install one layer of drywall double the thickness to acheive your goal, which (as Eric mentioned) might well decrease the TL values of the wall assembly.

Green Glue creates a pliable inner layer which allows the sheets to move independently of one another - thus constrained damping rather than actually gluing the pieces together.

From a cost point of view - I've been conviniced by Audio Alloy that the product is indeed a cost effective solution IF you would be willing to install 4 layers of 5/8" drywall (per side) with an isolated framing assembly..

In fact I have just (for the first time) specified their product for a clients project.

In a case like your studio (however) I do not believe it would not be cost effective.

Your primary concern is not isolating value - you've already explained that you don't mind some bleed through and do not see the need for maximum isolation.

SO it all comes down to the depth of isolation one desires, the greater isolation desired - the more cost effective it becomes.

Sincerely,

Rod
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Re: Green Glue - Again!

Postby Wurlitzer » Mon Feb 20, 2006 11:19 am

Rod Gervais wrote:From a cost point of view - I've been conviniced by Audio Alloy that the product is indeed a cost effective solution IF you would be willing to install 4 layers of 5/8" drywall (per side) with an isolated framing assembly..

The question though, as we discussed at some length last time, is whether it's cost effective in comparison to simply putting more layers of drywall up (ie, "doing a Woodlock" :)) until you reach the same isolation spec that way.

On the face of it I think the extra drywall will work out much cheaper, but then of course one needs to include the time spent erecting the extra drywall, associated labour costs if one is paying contractors to do it, and the extra weight upon the studwork (and floating floor, if there is one).

Then there is the fact that GG doesn't take up significant space, whereas a few extra layers of drywall might lose you an inch or more of floor space all around the room - probably not significant for bigger rooms, but can be for smaller project studios where space is at a premium.

I was tempted by this last factor, but at the time I put up my walls there just wasn't enough evidence of exactly how much good it would do. I didn't need full-on total isolation so I just went with two layers of drywall for the inner room, with no GG. If I want to further deaden things, I may consider another layer or two of drywall later and use the GG then. I believe more information about it is becoming available now.
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Re: Green Glue - Again!

Postby The Byre » Mon Feb 20, 2006 12:06 pm

Hi Rod, Eric and Wurly!

At the moment my interest is purely academic, though I will be doing some work on a studio in the South of Scotland in the near future and so I thought I would look at this stuff as an alterantive to two solid block walls.

With drywall, I assume you mean what the Brits call plasterboard or the Germans call Rigips. I have always assumed this, but it is better to ask the obvious silly question, than to live in doubt!

My problem is that I cannot perform acoustic tests here as I do not have a test chamber any more. I used to have one in Germany - a barn with 80cm sandstone walls and one small window that I could use to test boards, glass, etc. But since we moved here, I have found other things to do! (Perhaps I'll build one, but then I have so many things on my plate right now . . .)

My eyebrows were raised by the almost utopian values that the manufacturer has claimed for this product, but they do not compare it to any other named product or structure.

It is all very well to shove in the words 'conventional glue' but which one? Silicon? Dots of silicon with an airgap? Multiple sheets of plasterboard as Wurly suggests? What?

As most people use silicon, this is the product to compare it with, BTW, so is this what is meant by 'conventional glues?'
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Re: Green Glue - Again!

Postby Wurlitzer » Mon Feb 20, 2006 12:33 pm

The Byre wrote:My eyebrows were raised by the almost utopian values that the manufacturer has claimed for this product, but they do not compare it to any other named product or structure.

It is all very well to shove in the words 'conventional glue' but which one? Silicon? Dots of silicon with an airgap? Multiple sheets of plasterboard as Wurly suggests? What?

As most people use silicon, this is the product to compare it with, BTW, so is this what is meant by 'conventional glues?'

Sorry Andy but, with respect, you're still not quite "getting it".

Green Glue shouldn't really be called a "glue", because that's not its actual function. It's just a shame that the manufacturers chose to call it that, as you're not the first one that has made this mistake.

The function of GG is to provide a "constrained layer damping system" which basically absorbs vibrations passing between the two sheets of drywall, turns them into heat and dissipates them before they get out the other side. It doesn't actually "glue" the sheets together at all.

Actual glues, on the other hand, will cause the two sheets of drywall to function as one thicker sheet, which is a completely different thing. They are not even attempting to do what GG is doing, so comparing them doesn't really make any sense.

Since GG is a soundproofing technology, it's more relevant to compare it to other soundproofing techniques that you could spend your money on instead - eg adding extra drywall, increasing the airgap etc. It's not an adhesive, so there's no point comparing it to other adhesives.

And yes, dryall = plasterboard.
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Re: Green Glue - Again!

Postby Juju Money » Mon Feb 20, 2006 3:46 pm

The Byre wrote:With drywall, I assume you mean what the Brits call plasterboard or the Germans call Rigips. I have always assumed this, but it is better to ask the obvious silly question, than to live in doubt!

Your assumption was spot-on. US "drywall" = UK "plasterboard". That's as qualified as I get in this discussion, interesting though it is ;)

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Re: Green Glue - Again!

Postby Eric Desart » Mon Feb 20, 2006 4:25 pm

http://www.earsc.com/pdfs/engineering/understandingdamping.pdf

Green Glue shouldn't really be called a "glue", because that's not its actual function. It's just a shame that the manufacturers chose to call it that, as you're not the first one that has made this mistake.

The function of GG is to provide a "constrained layer damping system" which basically absorbs vibrations passing between the two sheets of drywall, turns them into heat and dissipates them before they get out the other side. It doesn't actually "glue" the sheets together at all.


It is indeed not meant to glue as a primary function, but without gluing them it shouldn't work either that way.
If one should apply GG on the outside of the panel, not much should be left of the effect.

If one compares both by GG connected panels where they meet than one notices that a crest in one panel is a through in the other.
Hence one gets significant shearing deformation which partly dissipates in the viscoelastic layer as heat.

It's not as if the vibration comes into one side of the double GG glued panel, then encounters some kind of viscoelastic insulator which then should pass a lower vibration level towards the next panel exiting with a lower level at the other side.
The vibration level on both sides (incident and outgoing) of the double panel glued with GG is about equal.

It strongly increases the internal damping of the whole combination drywall/GG/drywall

As I told in another message, noise does not go through a mass, but brings the whole thing in vibration which then brings the air at the other side in vibration. The CLD damps this vibration level of the total combination.

There is a direct analogy between the insulation value of a panel and it's internal damping, and the fact that absorption will lower the sound level in a room by adding absorption (damping on the sound field), assuming a constant source and a approximate diffuse field.

When one compares e.g. thermal insulation of a brick wall with acoustic insulation, then one notices that the temperature within the wall will gradually decrease from the inside to the outside temperature.
With acoustic insulation that's not the case. If one has a 40 dB insulation the vibration level on the outside of that brick wall equals the vibration level of that wall on the inside of the room.
Which in other words means that that wall radiates as much sound back into the room than to the outside.

Best regards
Eric
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Re: Green Glue - Again!

Postby Eric Desart » Mon Feb 20, 2006 5:56 pm

The Byre wrote:

It is all very well to shove in the words 'conventional glue' but which one? Silicon? Dots of silicon with an airgap? Multiple sheets of plasterboard as Wurly suggests? What?

As most people use silicon, this is the product to compare it with, BTW, so is this what is meant by 'conventional glues?'


Andy,

One of the major conditions for damping is dissipation (absorption) of energy.
In this type of application this assumes a viscous or viscoelastic material. It's the viscous part absorbing the energy.
An elastic material does not dissipate energy but stores this energy and gives it back.
Silicone is very much an elastic material and as such not a good damping material.

Best regards
Eric
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Re: Green Glue - Again!

Postby Rod Gervais » Mon Feb 20, 2006 7:50 pm

The Byre wrote:Multiple sheets of plasterboard as Wurly suggests?

Byre,

The break ahead point for this material is 4 layers of drywall each wall face.

If you plan on using a design that will only use 2 or 3 layers of drywall - with standard construction techniques - then even through the green glue will give you more bang for your money - it will cost more than conventional techniques.

However - if your plan includes the isolation gained by installing 4 sheets per side - then all indications are that you can acheive the same results - slight advantage in the higher frequencies (but that isn't the critical area of concern really) with 2 layers each side and green glue between the 2 layers.......... There is also a slight advantage around 100Hz with this application.

Anything prior to that is not cost effective.

The client I specified this material for is constructing side by each practice rooms for bands - and room to room isolation is quite critical.

Sincerely,

Rod
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Re: Green Glue - Again!

Postby Eric Desart » Tue Feb 21, 2006 9:23 am

Rod,

Can you translate that in numbers?
How much cost applying GG per surface unit (sft or m2) per glued layer versus not gluing. (hence the absolute added cost). Since you calculated it for a project, you must have a good picture.

1 Material (base on which cost per material unit = prices maybe differ per geographical area)
2 Labor (in cost and average time = hourly rates can differ geographically).

3 Total

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Re: Green Glue - Again!

Postby The Byre » Tue Feb 21, 2006 12:13 pm

I am find this all quite interesting, but a couple of points here:-

1. Reading through all the above, it does not seem that anybody has tested GG and we still have to take the word of the manufacturer.

2. Plasterboard is unbelievably cheap and cutting with a carpet knife and fixing with small dabs of silican or whatever is a totally unskilled opperation, ideal for the DIY'er.

3. By the time you have put up all kinds of 2 x 4 (inches) and double plasterboard and GG, would it not be much easier to just throw up a solid brick wall? Bricks, mortar and a brickie are fairly cheap too.

4. One material I have never tried for a studio (though I did use it for a bathroom once) is Ytong (a type of foamed light concret block - Eric is bound to know this stuff). In the UK, Ytong does not seem to be used at all.

5. I have only ever built studios out of brick. I can imagine needing some magic stuff like GG for converting a wooden structure, where sound can travel down joists to just about anywhere in the building, though it would be nice to see GG compared to other materials and methods that work - and not just to methods that are obvious mistakes, like screwing plasterboard to a wooden frame.
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Re: Green Glue - Again!

Postby Wurlitzer » Tue Feb 21, 2006 1:28 pm

The Byre wrote:I am find this all quite interesting, but a couple of points here:-

1. Reading through all the above, it does not seem that anybody has tested GG and we still have to take the word of the manufacturer.


Yes, this is definitely a problem. As I said above, there certainly wasn't enough evidence to make me buy it when I was building. I was under the impression that had been addressed to some extent - have you been on the Audio Alloy site?

I remember Max saying he had just decided to try it out for a job he was doing, as would be keen to see the results. So if you're not in a hurry, maybe wait and see what he comes back with.

2. Plasterboard is unbelievably cheap and cutting with a carpet knife and fixing with small dabs of silican or whatever is a totally unskilled opperation, ideal for the DIY'er.


Of course, and this is probably the simplest way to approach the question of isolation (once you have a basic mass-air-mass system in place) - just keep putting more layers of board up.

On the other hand, putting the plasterboard up does take time, which you're paying for if someone is doing it for you. It makes the walls thicker, taking space you might not want to give up. I agree that for the majority of people, adding layers probably makes far more sense and is more economical. But for some professional studios, the price of a layer of Green Glue might not actually be that significant, and they're happier to save the hassle of putting up more layers, or there may be practical reasons why they can't.

3. By the time you have put up all kinds of 2 x 4 (inches) and double plasterboard and GG, would it not be much easier to just throw up a solid brick wall? Bricks, mortar and a brickie are fairly cheap too.


That has certainly occured to me, particularly AFTER all the palava of erecting a stud wall in my building! Note that studio construction is always double-skinned - ie, there are two, separate and ideally non-connected walls. I expect in most cases the external one will be brick or block pretty much automatically. Plasterboard walls are then used for the inner wall, and for internal walls separating rooms within the structure.

Now with each of those walls that separate rooms within the overall structure, you want ANOTHER mass-air-mass system, ie another set of TWO walls with an airgap in between, for maximum soundproofing. So to achieve this with brick, you'd need TWO brick walls, not one.

There are several possible reasons why this might not be practical. So much brick might be too heavy for the foundations of the building. If there are floating floors, the amount of weight added by brick-built walls may make their design impractical, etc. etc.

As for the internal of the two walls around the perimeter of the structure, I was originally going to build this out of brick in my (one-room) studio. However there were severla problems. UK building regs state that any structural masonry wall has to be a certain minimum width, or have piers placed every so often to strengthen it. That would involve accomodating the piers into the internal design of the room. Also, a double masonry wall like that is supposed to have wall ties connecting the two walls, which would compromise the effect of decoupling them and make the mass-air-mass system not work so well. Whereas plasterboard walls are not subject to such regulations. There were other factors as well in my case, so I ended up just going with a plasterboard inner room. It's worth noting that before I built the building, I had conversations with two studio-building firms (both of who were way out of my budget, hence ending up doing it myself), and both of them suggested this kind of structure - masonry outer wall and plasterboard inner. Primarily because of the issue with the wall ties.

I remember Tim Rainey at the time saying that his studio in Greece was built with an inner room of brick. But then in Greece they probably don't have building regs. ;)

In principle I agree with you that brick walls might be a simpler and more effective way to go. However accomodating that much weight into a double-skinned system, and satisfying UK building regs in the process, is not necessarily that simple. But if you can do it, I reckon it would work great.
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Re: Green Glue - Again!

Postby Eric Desart » Tue Feb 21, 2006 1:39 pm

The Byre wrote:
1. Reading through all the above, it does not seem that anybody has tested GG and we still have to take the word of the manufacturer.


Andy,

1. That's not completely true. Several people follow this GG from the beginning it became known publically.
At the AVS forum (Home theater forum where they are addicted to subwoofer range) they use it regularly, most (all?) respond enthousiast.
The designer of the stuff is member here ( :D you can be sure he follows this thread)
Brian Ravnaas is mainly active here:
http://www.avsforum.com/avs-vb/member.php?userid=7456319
You can find countless messages related to GG and people who applied it there.

We followed a lot of post where Brian did all his investigative measurements, entering lots of this experimental data. Brian is a scientist with a lot of in-depth background, with a scientific attitude and knowing exactly what he talks about.

The principle phenomenon of internal damping is a known phenomenon, including it's relation to transmission loss.
Hence the measurements in function of damping can be seen and checked versus known data and as I said are about unique leaving little room for improvement.

I do agree that the comparison as stated in:
http://www.audioalloy.com/c10-00_STC/AudioAlloy-GG-STC.pdf
is a typical commercial approach which I don't appreciate at all.
They use a standard wooden stud wall without absorption as the reference wall calling it a normal wall.
Well for me that's very simple: If somebody wants sound insulation than a wall without absorption is not normal at all and direct screwing to wooden studs is a worst case situation influenced by structural resonance as well.
When I shouldn't know more about the stuff and better knowing Brian, this page should cause me not to trust Audio Alloy as well. That's not a technical page but a commercial hype one.


The Byre wrote:2. Plasterboard is unbelievably cheap and cutting with a carpet knife and fixing with small dabs of silican or whatever is a totally unskilled opperation, ideal for the DIY'er.

2. Is true but has nothing to do with the topic at hand as explained before. The gain of GG is CLD. The silicone suggestion is fun and easy but senseless and can even be harmful.


The Byre wrote:3. By the time you have put up all kinds of 2 x 4 (inches) and double plasterboard and GG, would it not be much easier to just throw up a solid brick wall? Bricks, mortar and a brickie are fairly cheap too.

Nobody claims that drywall with GG is a better solution than brick walls.
In the States (and probably lots of other countries, hence is geographically dependent) drywall based on wooden studs seems fairly standard.
Here drywall is mainly used in utility buildings as e.g. office buildings and in the DIY world.
And 95% of the utility applications is NOT with wooden studs, but dedicated metal framing which in itself will show better results than what's on the Audio Alloy site called a normal wall.
For me there's nothing normal about that wall. That's the worst version one can build with drywall. Certainly when TL comes into the picture, which is the reason GG exists.

But GG IS good. When one chooses to build light-weight walls, gypsumboard double leaf walls are about the most efficient option.
Double leaf walls are limited by some phenomena, mainly the mass-spring resonance (and in that so-called normal wall the structural resonance) and higher up the coincidence but which mostly isn't that defining in the overal insulation.

What GG does is OPTIMIZING such walls, which indeed can show significant improvement.

Further in Studio terms it certainly can have advantages because one suppresses the drumskin effect undamped panels can show much more enhanced.
In fact GG makes the panel sandwich as dead as possible, and I do believe better than anything I saw before.
GG doesn't leave much space (if any) for improvement.


The Byre wrote:4. One material I have never tried for a studio (though I did use it for a bathroom once) is Ytong (a type of foamed light concret block - Eric is bound to know this stuff). In the UK, Ytong does not seem to be used at all.

The basic idea of insulation is isolating above the fo (mass-spring-mass) and below the coincidence.
A) Hence trying to get the first as low as possible and the second as high as possible (what GG does is suppressing or minimizing the negative effect of this).
This assumes ligh-weight walls which are called flexible walls. Below the coincidence the radiation degree of a panel is lower than 100% or 1. Hence this means that the measured vibration is not all converted into radiated noise (there is some natural anti-noise in front of the panel caused by the neutralizing pressure effects of adjacent crests and throughs).

B) shifting the coincidence that far downwards that it lies below the frequency range of interest.
This by definition assumes very heavy stiff walls (brick, concrete etc.).
I this range above coincidence there is a radiation degree of 1. The wall acts as a stiff piston. Every bit of vibration measured is converted in radiated sound.

C) The Ytong, or whatever other cellular concrete, or thin gypsum blocks, or whatever other type of wall with an in-between mass will cause the coincidence to lower to the mid-range area right into the center of interest in function of insulation (one calls that the insulation plateau which can be wider than 2 octaves). It also calls for much larger cavities in function of MSM (mass-sprring-mass).
Hence it's nor one (flexible), nor the other (stiff) and is not a logical choise if not forced to make such choise for other parameters.


The Byre wrote:5. I have only ever built studios out of brick. I can imagine needing some magic stuff like GG for converting a wooden structure, where sound can travel down joists to just about anywhere in the building, though it would be nice to see GG compared to other materials and methods that work - and not just to methods that are obvious mistakes, like screwing plasterboard to a wooden frame.

As said. GG doesn't present itself as a substitute for complete other approaches, but for what it's meant for.
And for that it does an EXCELLENT job. And I never saw better related damping values as measured/published by Brian and I don't doubt for one second they shouldn't be representative.

Brian has made measurements comparing different mounting methods including dedicated rubber decouplers, Resilient chanel and so on.
And indeed those measurements prove GG to be superior.

I don't know if it's on their site. And I also agree if I find a comparison as I linked above and you probably referred to, I don't feel like searching any further.

Hence I defend GG, by understanding the phenomenon. seeing those CLD measurements, but mainly knowing and blindly trusting Brian, the related communication and posts the last years.

If I shouldn't and should see this PDF, not knowing better, I should react exactly as you do. Forget that site, yet another hype thing .......

Kind regards
Eric
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Re: Green Glue - Again!

Postby mattm » Tue Feb 21, 2006 2:23 pm

i have spoken with a few people who have bought GG and they are happy, though they say it is sticky!

Max is away at the moment, he can relay hes initial findings on the product when he returns
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