Green Glue for Noise Reduction
Kiley Jacques
| Posted in General Questions on
Have any of you used Green Glue for noise attenuation? If so, would you recommend it? Why or why not?
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I've used it several times--seems to help but I have not had a control to compare it to.
Yes, I've used it, and yes, it works. It isn't a night and day difference, but it does help. Most of the "work" in the recommended assemblies (double layer of 5/8" drywall with green glue between the layers) is done by the double layer of drywall, with green glue only contributing a relatively small amount of decoupling.
I would recommend green glue if you want to optimize your sound "proof" wall, but can only fit a double layer of 5/8" drywall. The green glue does help.
If you want to cut down on sound transmission and budget is tight, just put up a second layer of 5/8" drywall and know that you're close to what you'd have if you used green glue, but at less cost.
If sound reduction is paramount, either go to a staggered stud wall with double 5/8" drywall on both sides, or hang your double layer of drywall on resilient channel. Either of these walls will perform far better than a regular stud wall with a double layer of drywall with green glue between the layers, but they cost more, they take up more physical space, and they are more complex to build.
I actually really like the staggered stud wall. Use 2x6 top and bottom plates and staggered 2x4 studs. Put a double layer of 5/8" drywall on both sides, with green glue if you want to maximize things, but it's not really necassary. Some mineral wool in the wall helps too. The staggered studs decouple the wall surfaces from each other and make a HUGE difference with little extra space, and with little extra construction complexity.
Note that in any soundproof assembly, it's really important to avoid "short circuiting" your efforts with things like electrical boxes on both sides of the same stud cavity. At least put them in different stud cavities, and try to use fire putty pads on the back of the boxes to reduce sound transmission through the box. It's amazing how much sound can leak through electrical boxes. I've found caulking the perimeter of the walls with acoustical sealant to be less of an issue, and I'd rank it about on par with green glue, probably a little less important than green glue, in terms of maximizing sound reduction performance of a wall assembly.
Bill
This is valuable, thanks Bill!
For what it's worth, we had our drywaller add resilient channel to a few walls during our remodel and he did so at no cost citing the materials were cheap and it added some spice to his work day. Not everyone might get so lucky but I don't think this should be expensive either. The main drawback with resilient channel is you lose some space. In our case, about 7/8".
Kiley,
Remember Green Glue is in that family of products like acoustical sealant and roofing tar that will end up on you, your clothes, your tools, truck, lunch, and when you get home your pets. Horrible stuff to use
I won’t be using it (especially given what you have shared—my cat!). An FHB podcast listener was asking about it and I want to be able to share some real-world experience with him. Your input is appreciated, thanks very much, Malcolm.
Green glue works very well when every other detail is done perfectly. If you are building a proper well sealed double stud wall with two layers of 5/8, it does make a difference.
In most residential construction, there are too many flanking paths, improving the drywall sound absorption by a bit just does not make an appreciable difference. I've tried this with installing a layer of drywall over existing ceiling with GG, better but nowhere near as good a proper sound proof ceiling.
The one product I really like is the Green Glue Sealant. This a great sealant for any air sealing, easy to apply and cleans up with water. Much better than the typical solvent based acoustic sealants. Running a bead of the sealant around the perimeter of any interior partition before taping makes a big difference for sound.
Does Green Glue Sealant work well as an air sealant at the sill plate, running a bead over and under the standard sill sealer, like people use Tremco Acoustical Sealant for? Green Glue is readily available at my local Menards, and the Tremco stuff is nowhere....
It might work for that but it skins over and I haven't tried pulling it apart after it fully cures, so I would not rely on it. A similar-looking product that is an excellent replacement for acoustical sealant is Pro Clima Contega HF. It's zero VOC (the opposite of Tremco), super sticky and has a pretty green color. You have to order it online but it's easy and usually in stock.
Ya, thought about Contega HF but it won't get here in time. I just laid down some Green Glue Sealant between some lumber and my patio. I also bought some DAP Dynaflex 230 (elastomeric sealant) and some Loctite PL Window, Door, Siding (polyurethane sealant), both rated for indoor and outdoor use, just to have something to compare to. What exactly will I be looking for when I pull them up? ---- Well, I just realized these won't be fully cured in time. The DAP and Loctite both say at least 7 days to fully cure. Green Glue just say 48 hrs "dry time". Is there anything meaningful I can surmise from my little backyard test in just 24-48 hrs of cure time?
Almost any sealant will work in the short term. You could use the cheapest painter's caulk and get good results at first. The test is how well does a sealant remain adhered (and whatever else you want it to do) years down the road. I don't think you'll learn anything useful in 24-48 hours, other than how easy it is to apply.
But if it’s sandwiched between a sill plate and foundation with literally the weight of the entire house squishing it, how important is its “sticking ability”? It’s not like this is being applied to an outside gap or crack or something. Plus, I’ll also be taping from Zip R9 to foundation as the main air seal at this spot. I’d just be applying the Green Glue under the sill plate as belt and suspenders.
Sound attenuation strategies often act counter-intuitively. Adding layers can make them worse not better. The safest way to ensure they will perform predictably is to use a tested assembly.
Part of this is due to resonances that aren't always easy to predict. That's why you can sometimes get better performance with uneven mixes of materials (like a layer of 5/8" drywall over a layer of 1/2" drywall on one side of a wall). Usually the usual double layer of 5/8" is the way to go, but if you're beefing up an existing wall with 1/2", adding the second layer as 5/8" is better than a second layer of 1/2" partly because the extra mass helps you, but also partly because you're less likely to have a resonanace somewhere when things aren't all the same.
A trick I've used many times to quiet down transformers in commercial buildings helps to illustrate how resonances work to amplify sound. Common dry-type transformers are all over in large multitenant buildings to step 480v (600V for our Canadian members :-) down to 120/208V service. The tend to buzz from the 60Hz AC line frequency, which for some fun physics is due to a property of the iron transformer core known as "magnetostriction", which means the metal changes dimensions slightly in response to the varying magnetic field of the AC line current. Anyway, the enclosures for these transformers are typically made of sheet steel, and they often tend to resonant at some harmonic of that 60Hz and make an annoying buzz.
My trick is to move my knuckle randomly around the face of the enclosure while pressing down on it. At some point, I'll find a spot where the pressure makes a BIG difference in the sound level. I either whack the panel right at that spot to dent it, which deforms the metal, or I stick one of the larger hardware store magnetics at that spot. The extra mass of the magnet, or the dent from the whack, alters the resonant frequency of the panel and you end up reducing the sound level, often significantly. You can do the same thing by gluing strips of drywall onto the inside surface of the opposite side drywall if you're only opening up one side of a wall. This is one place to NOT be OCD too -- things actually work better when you DON'T lay things out evenly in this case. It's also usually better to put things in at odd spacings (1/3, 1/5, etc.), instead of even spacings (1/2, 3/4, etc.).
Bill
You may to look at:
https://www.soundproofcow.com/soundproofing-101/guidetosoundproofing/
https://www.soundproofcow.com/new-wall-soundproofing-assemblies/
You have to be very carful with companies selling you specialty material for sound proofing.
For any house noise proofing, you only need a couple of very low cost materials that are readily available at your local box store and lot of elbow grease.
There are no magical materials that will sound proof your home, one of the biggest offenders is people selling MLV which does almost nothing (not quite as it does add some weight) when installed in a wall or ceiling.
To sound poof you need:
-air seal: a 95% air seal might only get you 50% of the expected STC value
-add mass: concrete/OSB/drywall all cheap, easy to install and double up layers
-isolate: double stud/floating walls/ceiling is the best. Resilient channel is cheap and simple, if you want better hat channel with isolation clips
-always add insulation. Doesn't matter which kind, they all work about the same.
That is it. No specialty items or magical engineering marvel needed.
I'll go one further than using low cost materials...I quieted down a drain line from an upstairs bathroom above a bedroom by using drywall scraps cut to 15" so that they could sit on the I-joist flanges. I then shoved in small cut off scraps of mineral wool around the pipes.
This almost entirely silenced the plumbing and it saved a bunch of waste from the landfill so it actually cost less to do this than to pay the dump fee. Assuming you count the small amount of DIY labor as free.
Where do soundproof panels like these fit in this story? Are they of any use?
https://sonopan.com/
Thierry,
After looking at the link it's still unclear. The STC rated assemblies they show don't seem to isolate the contribution the panels make. They may make a big difference, I just don't see how you tell.
"You have to be very carful with companies selling you specialty material for sound proofing."
I believe the SoundProofingCompany founders (Ted White) invented GreenGlue, and the assemblies on their site have been tested (the STC and IIC numbers are posted). If you ever give them a call they are incredibly helpful (without me even having made a purchase they offered to get on a call and have a discussion with my builder on how to approach things).
Be skeptical, sure, but SoundProofingCompany are good people from my experience -- anyone researching in this area would do well to do some reading on avsforum.com and the "Soundproofing master thread" also.
Agree there are 4 aspects to soundproofing - decoupling, absorption, mass, and damping.
Green glue helps with damping. My understanding is that as the drywall flexes (due to noise), green glue turns that energy into heat. It's but one piece of the solution however.
Thanks all, I will be sure to send the listener to this thread--there are some valuable nuggets here.