Green Glue

[ReneO]

This might sound stupid but I've honestly never
Heared if the stuff. What is green glue ?
Is it really green?
What are its uses read of it as Being used between
Giprock panels.
If I need it for my studio build where would I find it in Europe "Switzerland"
And what would if be referred to here.

[Soundman2020]

This might answer your questions:

http://www.greengluecompany.com/

Yes, it really is green. No it is not glue, and cannot be used as an adhesive. It is a "constrained layer damping" compound, meaning that it damps some types of resonance that occurs between layers of drywall.

- Stuart -

[BriHar]

Green Glue is not locally available in Switzerland nor Germany. There is a source in Austria but I wasn't able to find out the cost.
It is not an absolute necessity, and if you use fermacell (which is readily available in Swizterland) instead of the usual gipswand, you shouldn't really need it.

[Ted White]

Is Fermacell something other than a heavier plasterboard? If so, it's just a heavier drywall. No damping as with a damping compound in a CLD system. There you would see increased TL from the LF resonance point all the way through coincidence.

[BriHar]

Fermacell is made from recyled paper fiber and gypsum, so it is basically a kind of plasterboard, but much denser than common drywall. For a 15mm thickness it weighs 18 kg/m² compared to normal drywall (data from Knauf) which has a weight of 12.2 kg/m² for an 18mm thickness (14.4 for 18mm special firewall) and only 12kg for 15mm. Furthermore it has many properties which are far superior to normal drywall. it's exceptional ability to hold screws, it has a much higher impact resistance, and can even be used in flooring and external construction. It is inherently fireproof, and water-resistant, without having to buy special variants as one does with drywall (though there is a more waterproof version). Something else that is possible with Fermacell that you could never do with drywall - you can soak it in water for about 8 hours, take it out and clamp it to a form. Upon drying it resumes all of it's original properties, and you now have a custom formed (curved) wall panel (Great for those curved plane diffusors, not to mention the possibilities for custom waveguiding walls for an RFZ).

There is no doubt that adding Green glue would even further enhance the TL of a construction using Fermacell over drywall, but if the GG is difficult to get here, using Fermacell over drywall will give better performance, so that the lack of GG will not be as significant.

Searching for Green Glue here brings numerous hits for a product called "Scotch Green Glue Universal" which is something totally different. I guess "Green Glue" is not a Registered Trademark.

[Ted White]

Thanks for the explanation. A more massive panel is more massive, but that is all. No damping, no decoupling, just mass. More mass doesn't negate the need for damping or decoupling. One component does not replace another. Better tires on a car doesn't reduce your need for brakes.

Consider installing as much mass as practical on the widest framing possible, to introduce as much flex as possible.

[ReneO]

Thanks for the info guys. That'll help making decisions on What to use for my Build.

[ReneO]

For my inner walls I used first a layer of normal Giprock panels and then a layer of these
http://www.knauf.de/content/de/trockenb ... lten_2.php
Did that so I would have varying mass from the layers. Contemplating doing a third layer. Would that be of any use for my CR. Or just over kill
I Had to buy special screws to get the screw heads to sink level with the surface. They are so dense.
)

[Soundman2020]

Did that so I would have varying mass from the layers.

That is not necessary. It's a myth that you need to vary the thickness of the layers. Yes, it does have a small effect, but it is not as effective as having more mass. So it is better to have each layer as massive as possible: 16mm fire-rated drywall.

Contemplating doing a third layer. Would that be of any use for my CR. Or just over kill

If you do it on all sides (all walls and the ceiling) then it will improve isolation, for sure. The question is: do you need to do that? How much isolation do you need, and how much are you already getting? It might be that you don't need the extra layer if you already have enough isolation with 2 layers.

- Stuart -

[ReneO]

Surrounding walls floor and Ceiling are all 25cm plus thick concreat walls with exception to the walls going to adjoining rooms such as the heating room with a heat pump. And the LR

Isolation requirements are for a CR and tracking vocals. The LR will have Accoustic Drums etc. in so more than 100dB at times in adjacent room.

? As for varying mass walls wouldnt it make sence to have varying mass between the 2 different leafs of the rooms eg. 3 layers on one leaf one 2 layers on leaf 2 ?

[Ted White]

I would say you are over-thinking this. You want decoupled framing, some absorption in the cavity and as much damped mass hanging on the decoupled framing as practical.

[Soundman2020]

As for varying mass walls wouldnt it make sence to have varying mass between the 2 different leafs of the rooms eg. 3 layers on one leaf one 2 layers on leaf 2 ?

Not really. The resonant frequency of the MSM system is governed by the total mass on both leaves ("m1 + m2" in the equations). If you have less mass on one leaf, then you have less mass in the entire system, and therefore the resonant frequency is higher, and isolation is reduced. Also, isolation in an MSM system is optimal when the mass is the same on both leaves. If you would like to understand the details of why that is, take a look at the Wyle paper from 1973: it explains that pretty well.

But like Ted said: you seem to be over-designing this. With two layers of 5/8" fire-rated drywall on each side of a deep cavity with plenty of insulation, plus Green Glue between the layers, that is going to give you really good isolation in your walls. The challenge will be to get the same level of isolation in your doors, windows, HVAC and electrical system.

There's nothing wrong with putting 3 layers on each leaf if you really need it, but that's a lot of extra money, time and effort that might not really be needed.

- Stuart -

[Ted White]

The challenge will be to get the same level of isolation in your doors, windows, HVAC and electrical system.

That's the best statement in the whole thread.