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# Green Glue - Page 5

hey Tedd, that's incredible - \$5 more a sheet than regular 1/2" ....

here, in the last year, it has ranged from a buck more to less than 1/2", must be the old supply/demand.

i'll run some calculations based on changed mass to estimate the performance difference at very low frequencies and get back
That IS odd. Some places sell 3/8", 1/2" and 5/8" all for the same price.
As for the comparison with a rubber layer, I can't speak to it myself, by my contractor has used it before, and I understand it was a pain to use. The Green Glue is much simpler, and from what I can tell, should work as well if not better.
Again. Does it have the same isolation benefits as rubber? Remember. Rubber, Acoustiblok, has mass, lots of it. The more mass you can build, the better isolation. So, how can a glue have the same mass factor as rubber?

If your building walls with rubber and drywall, your talking major mass. If using GG, where's the mass?
ok, with respect to mass and sub-region performance on a 2x4 wall, the following calculations may be handy, they are based on the expected changes due to mass alone.

IMPORTANT NOTE: these will probably apply well in the subwoofer region, they will not apply at higher frequencies at all,

These are relative to one layer of 1/2" drywall on both sides:

double 5/8" both sides: +8 dB
5/8" + 1/2" both sides: +7 dB
double 1/2" both sides: +6dB
double 3/8" both sides: +3.5 dB
5/8" + 3/8" both sides: + 6dB
1/2" + 3.8" both sides: +4.9 dB
5/8" + 1/4" both sides: +4.9 dB

single 5/8" one side, double 5/8" other side: +5.5 dB
single 1/2" one side, 1/2" + 5/8" other side: +4.2 dB
single 1/2" one side, double 1/2" other side: +3.5 dB

(TEDD: from this calculation, it looks like utilizing 1/2" drywall in lieu of 5/8" drywall would cost you 0.7 dB if you were upgrading one side, and 1 dB if you were upgrading both sides)

single 5/8" both sides: +2 dB
single 1/2" both sides: +/- 0 dB

to convert from one possible construction to another, just subtract the two numbers.

i.e., for 1/2" + 5/8" to 2*5/8", take +8 minus +7 = 1dB of gain in this region for the heavier wall, etc.

i guess that's a few of the permutations, and it must be stated again that these predictions ARE NOT for all frequencies, but should apply reasonably well to frequencies below about 80hz and above wherever the wall resonates as a panel.

there are two low frequency resonances in this type of wall, the first tends to occur in the 80-200hz region, and the second much lower (perhaps lower than 30hz, or even at extremely low frequencies). Performance of all walls at resonant points is damping controlled, not mass controlled, performance of the walls at mid/high frequencies will depend on a wide variety of factors, and the extra mass of 5/8" drywall will not neccessarily be an advantage. BUT:

over the bulk of the subwoofer range, mass will be the most important factor (for an ordinary 2x4 wall), and the above should hold reasonably well.

to compare the above data to lab tests:

moving from 1 layer of 1/2" on both sides to 1 layer of 5/8" on both sides has a predicted benefit of +2 dB

in lab tests it delivered (average) +2 dB (IR-761)

for 3 total layers of 1/2 (1 one one side, 2 on the other side) the predicted benefit is again +2 dB, and test results showed +2.7 dB... (again IR-761)

generally, the data that i can find to browse shows results within ~ 1dB of the prediction for mass change in this region.

LET ME KNOW IF THIS ISN'T STRAIGHTFORWARD ENOUGH
Quote:

Originally posted by vitod
Again. Does it have the same isolation benefits as rubber? Remember. Rubber, Acoustiblok, has mass, lots of it. The more mass you can build, the better isolation. So, how can a glue have the same mass factor as rubber?

If your building walls with rubber and drywall, your talking major mass. If using GG, where's the mass?

Ok, let's talk about mass for a moment... A sheet of 5/8" drywall weighs 70-75lbs... or about 2.3 lbs/square foot

if we added a layer of roofing rubber that was 0.8 lbs/square foot to a wall with 2 layers of 5/8" drywall on both sides, we'd raise the mass from ~9.2 lbs/square foot to 10, or about <10%

by mass calculation, that would translate to 0.7 dB of added performance.

if we added rubber at 0.8 lbs/square foot to a wall with just 1 layer of 5/8" drywall on both sides, we'd anticipate 1.4 dB of improvement.

if we used heavier, 1lb/square foot material, the impact on performance due to mass would be 0.9 dB and 1.75 dB due to mass for the two cases respectively.

so, the added mass of rubber simply isn't/can't be a considerable factor in performance.

looking at cost... let's say that our 1lb/square foot rubber cost 2 bucks a square foot. that's 2 bucks a pound. Drywall costs maybe 8-10 cents/lb.

so if you want more mass, add more drywall, seems alot cheaper.

anyway, to the question at hand: if adding a rubbery product to a wall has a transformative effect on sound-stopping performance, it's not due to it's mass, the mass is trivial.

it would be due to damping or some type of isolation effect (like rubber pucks, perhaps), or changing in the resonant behavior (moving it to a lower frequency to get higher STC). it's not the mass. you have to add ALOT of mass to really change walls. Now, drywall is stiff and very resonant and transfers energy very well, so perhaps roofing rubber attacks the resonance (damping) or the transfer (some isolation effect)

Roofing rubber isn't a practical or meaningful mass loading material, either, so it's effect has to be something else.
oh, hey, Vitod, i guess i got carried away talking about mass and didn't answer the

"which is better" question directly.

To the best of my knowledge, nobody have ever publicly offered a comparison of wall performance with and without limp mass, or even jsut with limp mass to leave us to guess as to what performance was like without it. that makes answering your question a bit harder, no? lol

i can simply say again that the mass of a roll of roofing rubber is largely inconsequential - drywall is far, far heavier, and it doesn't have a big change on overall mass.

and i can say simply that Green Glue is overwhelmingly superior as a damping material. limp materials have one big advantage over drywall - they aren't resonant. Well, Green Glued drywall isn't either (and it's cheap)

we have a large number of 3rd party tests now and in the near future, perhaps we'll pony up a nickel to answer the great limp mass question. Green Glue users won't be dissapointed. If we can squeeze it into our time/budget, we are also going to include non-green walls for as many of the cases as possible... since it's not feasible, or remotely, to compare data from lab to lab, that would give Green users the best idea of how things stack up possible.
So, rubber mass is not necessary as long as you have damping. For example:

stud>GG>drwall>GG>drywall. Correct?

What would be the STC more or less?
The rubber is not necessary and overly expensive for little to no benefit.

STC is meaningless for this application.
hey vitod, we'll release the tests when they are completed, and they'll have the STC calculations...

but what DE said holds: STC is just not a great measure of sound stopping at all.

STC disregards everything below 125hz, and even from 125-4000hz (the frequencies it does consider), it's calculation method is... not so good.

it stems from long, long ago when modern calculation speeds just weren't possible and a manual method for determining a rating was necessary.
Tedd:

Quote:

I've just received a couple of pails of Green Glue to get me started

By the time you paid for import duty and/or goods & services tax, and customs brokerage fees if necessary, what was your final cost in Canadian \$ ?

Thanks ... /FP
You have a pm, Ford Prefect. I guess I won't have the final costs until the charge card bill comes, but the Canadian dollar has made some impressive gains on the US dollar as of late. Sure beats a 50% premium I was paying as little as two years ago....
I have read the application notes .pdf from the website, but have a few questions:
1. "adhesive trowel" is this like 1/8" tooth vinyl trowel or a 1/4' tooth tile trowel?
2. What has anyone found a the best applicator for studs? same trowel? what about a "cake icing bag" type thing?

thanks!
I have a slightly different application that I don't think has been covered in this thread. My dedicated theater room has three exterior walls and I get a very resonant - if that's the right word - noise from outside passing traffic. We live in a developing neighborhood and there are a lot of work/delivery/utility vehicles that rumble down the lane. The walls of the room seem to amplify certain frequencies from the trucks and is REALLY distracting and quite loud. The facing wall is on the second floor and is about 25 feet from the road. The construction is 1/2 drywall+2x4 w/roll insulation+3/8 OSB+Tyvek+Hardiplank. Can I expect much attenuation of the low frequencies of the kind I am hearing via an application of GG and a layer of 1/2 drywall? Is another application more appropriate for this issue? Thanks!
hey sandwedg

1. is covered for you, you get the proper tool with every order

2. is something under research right now. The drywall tool works well, but improvements might be possible. A cake icing bag is a pretty slick idea, i'll have the lab gents take a look. filled conventional caulk tubes might be on the horizon
Bluetone

g'morning.

a quick side note: we experimented with some constructions once just to see if actual amplication of noise across a wall is possible in a case of severe resonance. the answer is affirmative, but that is a very tricky thing to measure with precision for a variety of reasons. i don't think the normal tests would ever reflect such a case.

on another quick side note: i worked in a building a few years back now that upgraded it's brick walls for higher STC. same effect, the low frequency resonance was so bad that the garbage trucks almost scared you if you were lost in thought. no high frequencies coming through, though! lol

with respect to your application, that is Green Glues very reason for being. do you have access to the outer part of that wall? can you treat (from behind, etc.) the OSB or whatever faces the street?

Brian

hardiplank / tyvek / 3/8" OSB / stud / drywall

at this time?

is there an air space between the hardiplank and the OSB? that's siding, right?
I just broke out the Green Glue last night and used the trowel to apply to the studs in the AV closet. It was time consuming for a single sheet and I doubt I'd have the patience to do a long run of studs this way. After reading the cake icing bag idea, I am wondering if the idea of a cake icer might be a good application tool. It is like a smaller version of a caulk tube (But refillable) and I wonder if the there is a suitable nozzle available to lay down a pattern similar to the notched trowel? As the Green Glue cleans up easily with water, this might work.

I just did a quick knuckle rap test on the 1/2" drywall/Green Glue/stud wall and the opposite wall 1/2" drywall/stud wall and I am impressed with a noticeable improvement in the wall already.
Brian - Yes, that is the construction. No air space between the OSB and the Hardiplank (fiber-cement siding), just house-wrap. I'm afraid that I can't get between the siding and the drywall w/o a crowbar. We just had the siding installed as a replacement for synthetic stucco. The noise level was more tolerable with the stucco. Are you thinking that the GG sandwich might be more effective somewhere other than between two layers of drywall?
hi all

Tedd, if you apply the Green to a sheet that is lying down by just scooping some on and spreading it, it goes pretty fast after a sheet or two. we just finished a survey of a couple of crews and also a few individuals and got ~4-5 min/sheet. I konw results will vary, i can't do a sheet in that time, and i think a video or two of that would help, i'll nag! anyway, good luck with the rest.

if you're working over an already painted wall, it's best to put the green on the painted surface.

Blue - i was just wondering if there was any way to damp the OSB, that's all. stucco is heavy, that helps with noise. Adding drywall + green to the inside should do very well if you can't access the OSB

Brian, I just applied the Green Glue to the stud itself but after reading your suggestion, it just clicked in, that it makes more sense to apply it to all the sheet, on the first drywall layer. It is a dampening material after all... Somehow I had it in my mind as a "sandwich only" application. I still have access to the rear of the drywall to correct this. As this wall is common to a separate laundry room and a separate furance room, it is getting double drywall/Green Glue on both sides of the wall, studs filled with Roxul and a layer of Sonopan noise blocker.

Some of my construction is a retrofitting a second layer over existing 1/2" painted drywall (three exterior, insulated walls with pored concrete walls), with the common wall and ceiling pretty much being all new construction.

I was planning on running most of my drywall vertically. Buttering the rear of the drywall and standing it into place, horizontally applied, sounds alot easier then manhandling a 75 pound sheet of drywall, with sticky Green Glue applied, four feet off the ground for the upper horizontal run.
Good morning all,

The Green Glue is a part of a constrained layer damping system. To operate at maximun effectiveness, the Green needs to be applied in between two rigid layers. This can be two layers of drywall or two layers of subfloor, etc.

A sandwich is, in fact, what is needed.

Thanks!
Ted White just called me not two minutes after my last post and to clarify my misunderstanding:

Green Glue is to be used as a sandwiched material between two layers.

I expect Brian will get around to clarifying this but I don't want to be misleading anyone to wasteful use of their Green Glue.

Edit: (Boy oh boy is Ted White ever fast....!)
hi all,

Green has to be a sandwich, it can be effective only when sandwiched between two things.

there are two basic types of damping materials

1. constrained layer damping materials (sandwich damping materials) - Green is one of those, and a really good one

2. extensionsal damping materials - they sit on top (coatings, pads, ) - Green is thoroughly futile as one of these.

about extensional damping materials: they will all be fairly futile on drywall. Drywlal is just too stiff, and the fundamental limitation of damping materials sitting on top (not a sandwich), i.e. extensional damping materials, is that they can't control resonance in stiff things.

so they work very well on sheet metal and what not, but VASTLY less well on things that are stiff.

some damping materials work in both applications, but generally only when very thick and generally not ideally in either application. For anything around the price it is usually easy to make something far superior if you design it for one application or the other.

i'll try to remember to come back with some charts to illustrate

Brian
Quote:

Originally posted by brianr820
hi all

if you're working over an already painted wall, it's best to put the green on the painted surface.

Brian,

I assume the reason for this statement is because GG is water based and cures by the evaporation of the moisture, not some catalytic process. Does the unpainted dry wall soak up too much of the moisture too quickly if you apply the GG to the fresh drywall first? It would obviously be easier in retrofit applications, to apply the GG to a piece of drywall on sawhorses in a horizontal position rather than to the vertical wall. Could this problem be solved by pre-moistening the fresh drywall panel with a damp sponge or some other technique?

i agree, it is very nice to put it on when the sheet is on the ground. after my comment today us lab chaps ran some tests on a painted wall where we put green on the new sheet, and laid it up, we'll report in about 7 days.

the convenience would be nice.

drywall does soak up water, good call, and Green dries faster in a sandwich than it does in open air as a result.

my thought was entrained air. the ridges from the trowel trapping little lines of air against the painted surface (the air can easily escape out through drywall/wood products, etc.)

one test will be done tomorrow (or monday if we don't have time to look at it tomorrow) to check for said entrapped air. if there is none, then in all honesty the other test is probably moot.

Brian
I post on installation when I'm done.
Can GG be used in addition to an In the Wall Barrier Acoustic Composite? Or would that be a waste of money? Thanks!
hey, i was just going to say "hi dork", then i realized you have an unusual screen name

do you mean mass loaded vinyl? and if so, do you intend to put the MLV in between two layers of drywall, or in the air cavity.

i think most MLV sellers recommend the latter

take care,

Brian
two more things

first - someone mentioned the other day my comment somewhere herein that 3 layers with 50% Green on each layer would give higher mass (obviously) and also higher damping that 2 layers with 1 layer of 100% Green.

and that's true, but this gentlemans comment was that the drywall was by far the biggest expense. and i guess that's a regrettable fact of construction, eh? the materials are cheap, getting them in place isn't necessarily cheap at all.

In any case, we just offered observations on 3 layer walls with 2 damping layers, and they are really nice, however... 98% of the work we've done is on 2 layers sandwiches, so use whatever your space/budget/time/patience/code allows.

Second thing - about putting Green on pre-painted walls.

It would obviously be overwhelmingly convenient to be able to apply the Green to the new sheet, and not the existing wall. I'd expressed some wonder about the entrainment of air.

we've ran these tests many times over now, and we have not observed that effect, so it appears i was incorrect. in this case that's a good thing.

we're going to continue to look at it, but it does not appear that there is any reason to not utilize the material in this manner.

TAke care all

Brian
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