I am curious how you guys think a standard wall (1/2" drywall-stud-1/2" drywall) with RC8 resilient channel and 2 layers of 5/8" drywall with Green Glue will perform.
How many leaves would that be? does the RC8 cause an air gap therefore making the wall 3-leaves? If so would it help if I cut out holes in the existing drywall?
Also my ceiling is one layer of 1/2" drywall, how would it do with RC8, 2-layers of 5/8" and GG?
Please see attached picture:
Resilient Channel & Green Glue vs. M-A-M wall?
Originally posted at johnlsayers.com, topic 15655.
I would not recommend resilient channel for several reasons. Decouple with clips and channel, but not with existing drywall. You should remove the drywall or face very limited improvement due to the triple leaf. Using channel directly on the ceiling is a commonly used example of what not to do.
I would also suggest stepping the drywall up to double 5/8"
That isn't a 3 leaf is it Ted? Wouldn't that be a coupled assembly with an additional leaf, and the small air space between the added sheetrock plus this coupling of the assembly... wouldn't that be the reason for the loss of isolation...or no?
I may be completely reading the diagram wrong Brien. I took it as an existing ceiling with plasterboard. Standard coupled double leaf. Then there was the proposed rc channel and more plasterboard. That's the triple leaf. Maybe im not following properly. Sorry if that's the case.
Most likely dichotomy. A coupled assembly is that...coupled, and I haven't seen it mentioned as a two leaf...a two-sided assembly certainly. A free mass, uncoupled, and an air space, another free mass, uncoupled and an air space and then yet another uncoupled free mass, that is a 3 leaf as I understand the terminology.
While I do not dispute the reference completely, it is to me, a misconception since the air in a coupled assembly does not have the same impact being bound as it is by the framing bays which produce a different result then free air applying it's medium, as it were, on the opposing boundaries.
Still....your answer is the most correct since it is essentially entirely too small an air space with entirely too much field of vibration from the existing boundary.
Hmmm. Well he started with a coupled double leaf assuming there's a floor on that ceiling. One air cavity. Then the channel and drywall give us a second air cavity, third leaf.
The NRC uses an example like this to show a very minimal gain relative to the effort. They only add a single layer of undamped drywall in that example so not directly comparable to the diagram. Then they show the same ceiling with the two drywall layers combined on the channel (one air cavity) and performance soars. I know you've seen this Brien so I still think I'm missing something. Apologies.
Thanks for the input guys!
I should have mentioned the ceiling has a layer of pink stuff and is an attic with ridge & soffit vents. I think that makes the ceiling a single leaf.
You guys think that removing the existing wall drywall will improve performance?
I do plan on using double layer 5/8 everywhere"
This is my garage, my hope is to make the room semi "normal" so that when I move out I won't have to deconstruct the entire room, I would like to be able to leave it up.
Well, it is an area of disagreement for me, and i don't recall a coupled assembly being referred to as a two leaf...so, if that is your information, I would like to see it, but I may have already and still came to the conclusion that I rest on. An example of how a ceiling/wall assembly is incorrectly defined as a two leaf would be to look at a concrete block wall. Concrete block wall is a one leaf I hope we can agree on that. But it has the same coupling front to rear and the same type of individual air spaces as a simple framed wall/ceiling sheathed with a mass material on either of the two sides. But it is a coupled assembly and we both know that this is a difficult assembly to isolate since adding mass can only be done in multiples until it becomes unreasonable/cost prohibited/structure resistant. tarnationsauce: You should update your location in your profile and add more information about what it is you are trying to achieve. It is true that a typical room, the ceiling and the roof above are a two leaf, mass/spring/mass assembly. So you could use that by adding mass directly to the ceiling rather than installing rc, and get what everyone is trying to get in this respect. But...there are things that have to be considered....and that requires details:)Hmmm. Well he started with a coupled double leaf assuming there's a floor on that ceiling. One air cavity. Then the channel and drywall give us a second air cavity, third leaf.
Actually, that makes it a two-leaf.I should have mentioned the ceiling has a layer of pink stuff and is an attic with ridge & soffit vents. I think that makes the ceiling a single leaf.
On the ceiling? No. Yes. Maybe. It all depends on what you are trying to accomplish. On the wall? Yes, definitely it would be an improvement to remove the existing drywall, then either add RC plus new drywall, or a separate from plus new drywall. The big issue with your current plan is the very thin air gap caused by the RC between two layers of drywall. Bad idea for isolation.You guys think that removing the existing wall drywall will improve performance?
Good!I do plan on using double layer 5/8 everywhere
I'm not sure exactly how the ceiling is constructed - you say it's an attic so does the attic have a floor??
I might add that you don't necessarily have to remove the drywall if it will create a triple leaf you just need to break the seal by creating holes in the drywall.
We had this situation in Ellamy studio ( http://www.johnlsayers.com/Pages/Ellamy.htm ) where there was a drywall ceiling and an upper floor - we just created holes in the drywall so the air in the cavities between the joists mixed with the lower room air.
Profile location updated. I hope to accomplish having a room that can be easily converted into a normal usable garage with little effort when I go to move out. I need to have as good of STC as I can so as not to annoy the neighborhood, or violate noise ordinance (60dBA). The closest sidewalk and house are ~15-20ft away. I plan on tracking hard rock with drum kit / bass etc. The outer roof has ridge vents the entire length of the roof, I thought that since it is not sealed that it would not act as a spring. When I am in the attic I can hear every little sound from outside. Perhaps is is a leaf but a very poor one?tarnationsauce: You should update your location in your profile and add more information about what it is you are trying to achieve. It is true that a typical room, the ceiling and the roof above are a two leaf, mass/spring/mass assembly. So you could use that by adding mass directly to the ceiling rather than installing rc, and get what everyone is trying to get in this respect.
I see, thanks! Yeah 1/2" air space seems very dismal. I will have to remove drywall.You guys think that removing the existing wall drywall will improve performance?On the ceiling? No. Yes. Maybe. It all depends on what you are trying to accomplish. On the wall? Yes, definitely it would be an improvement to remove the existing drywall, then either add RC plus new drywall, or a separate from plus new drywall. The big issue with your current plan is the very thin air gap caused by the RC between two layers of drywall. Bad idea for isolation.
The attic has a very minimal floor made of 1/2" plywood approx 4' x 12'. It would be easy to rip out if needed. It looks like cutting holes is the route I will take for my walls. Do you have an idea how large I should make the holes in order to effectively "break the seal"? Any tips to avoid hitting electrical/plumbing? "Breaking the seal" is why I am confused about the ridge vent (and soffit vents), the attic is clearly not sealed.I'm not sure exactly how the ceiling is constructed - you say it's an attic so does the attic have a floor?? I might add that you don't necessarily have to remove the drywall if it will create a triple leaf you just need to break the seal by creating holes in the drywall. We had this situation in Ellamy studio ( http://www.johnlsayers.com/Pages/Ellamy.htm ) where there was a drywall ceiling and an upper floor - we just created holes in the drywall so the air in the cavities between the joists mixed with the lower room air.
It doesn't need to be sealed in order to create a third leaf. All that you need is a large fairly massive surface on the other side of an air gap. Sealing improves overall isolation for other reasons, but the leaf is a "leaf" simply because it is a large surface, with appreciable mass, on the other side of an air gap. Somewhere there's a link to a report by a studio builder that illustrates this principle perfectly: he happened to hold up a large sheet of some material (plywood? drywall?) close to an existing MSM structure where loud music was playing on the other side. The simple fact of holding that sheet a few inches away from the wall was enough to re-tune the wall so that the resonant dip moved way up into the audible spectrum, and all of a sudden he could clearly hear the music playing on the other side of the wall. I'll see if I can find that link. I know I have it somewhere.... Regarding your question on cutting holes in the drywall: as John pointed out, that will work fine as long as the holes are large enough and there are enough of them to reduce the effect of that 3rd leaf. But if you are going to knock a bunch of large holes in your wall, then why not just take off that drywall completely? Not much extra work, and it would have the additional benefit of giving you access to the wall cavity, so you can add the (additional) insulation easily, if needed. Do you know if the existing wall is well insulated? Not putting insulation in the cavity correctly can cost you a lot of isolation. - Stuart -"Breaking the seal" is why I am confused about the ridge vent (and soffit vents), the attic is clearly not sealed.
stuart is back!!!
:yahoo:
That is a fantastic link to have, as it demonstrates the point so well. If you ever find that you'd be doing a great service StuartSomewhere there's a link to a report by a studio builder that illustrates this principle perfectly: he happened to hold up a large sheet of some material (plywood? drywall?) close to an existing MSM structure where loud music was playing on the other side. The simple fact of holding that sheet a few inches away from the wall was enough to re-tune the wall so that the resonant dip moved way up into the audible spectrum, and all of a sudden he could clearly hear the music playing on the other side of the wall. I'll see if I can find that link. I know I have it somewhere....
:) :oops: :blah: :shot:stuart is back!!! :yahoo:
:D
it was paul woodlock. http://forum.studiotips.com/viewtopic.php?t=1198 but i can't open the link =( here is one who copied the text into our forum greetings, carstenSomewhere there's a link to a report by a studio builder that illustrates this principle perfectly:
Thank you Carsten for digging that up. And thanks again Stuart for thinking of that.
Sound behaves in strange and seemingly non-intuitive ways. I think I get it now. lol Thank you Carsten for finding the link, and thank you Stuart for thinking of it. Very interesting indeed. :)It doesn't need to be sealed in order to create a third leaf. All that you need is a large fairly massive surface on the other side of an air gap. Sealing improves overall isolation for other reasons, but the leaf is a "leaf" simply because it is a large surface, with appreciable mass, on the other side of an air gap."Breaking the seal" is why I am confused about the ridge vent (and soffit vents), the attic is clearly not sealed.
I removed some outlet covers and discovered all the walls do have insulation (the kind with silver lining). I was actually thinking having the extra 1/2" of depth from the existing drywall would help isolation since it would make the wall air/spring cavity a little deeper. I am actually thinking of removing nearly all of the existing drywall except the areas where the studs are for that extra air gap. As for the ceiling, it sounds like RC would actually make the ceiling worse than if I were to directly apply a couple layers of 5/8" drywall with GG. That's good because it will save me time and money not having to buy and install the RC.Regarding your question on cutting holes in the drywall: as John pointed out, that will work fine as long as the holes are large enough and there are enough of them to reduce the effect of that 3rd leaf. But if you are going to knock a bunch of large holes in your wall, then why not just take off that drywall completely? Not much extra work, and it would have the additional benefit of giving you access to the wall cavity, so you can add the (additional) insulation easily, if needed. Do you know if the existing wall is well insulated? Not putting insulation in the cavity correctly can cost you a lot of isolation.