Green Glue - Page 16 - AVS Forum
Forum Jump: 
Reply
 
Thread Tools
post #451 of 1328 Old 09-19-2005, 08:27 PM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by krasmuzik View Post

It might be hard to believe that a large manufacturer wants to make more of the same stuff - so they come up with dubious uses for stuff - knowing that they can get the high school drop out contractors to install the stuff - being that they already know how to install their other stuff. Hard to believe indeed!

hi Kras,

your logic isn't flawed. i so dislike this topic (more on that at the end)

I offer comments from David Harris who seems to know alot more about the history of the product than i do (and i expand quotes to include a whole 4 paragraphs from the section above)

i offer what test data that i am aware of on this planet - that being the IR-761 and IR-693 comparison i listed above. And i offer that we paid a considerable chunk of change to commission a similar test with even lesser results, and i hypothesize as to why this might be.

i offer that (and i might be one of the bigger data-junkies around) there is no full band, or even non-full-band data of which i am aware falling in line with Fargo biulding code implying that soundboard outperforms drywall for full-band performance, or even STC. you can't glue with 6" stripes between studs in Fargo, ND, YMMV.

i offer that there is a big beautiful marketing brochure chuck-full of STC ratings from one particular lab. and i offer that data from that same lab for same designs, but replacing the soundboard with drywall routinely have higher STC's than the figures in said marketing report.

i offer that perhaps you could say that the NRC tests demonstrate that it's better pound-for-pound than drywall. i offer that drywall is heavier, making a layer-for-layer claim not as relevant. i offer that if no insulation was to be used, perhaps the sound absorbing qualities would have merit. i offer that the method discussed by the homasote corporation may have merit, and i offer that i'd check with local code before trying it.

and i dislike this topic, which is frequenctly asked. it makes me feel like i'm knocking the stuff, which i'm not. i don't insult it, i observe that not data exists to the best of my knowledge to support that it is an improvement over just another layer of drywall when screwed to the studs. it makes me wonder if people would read my posts and think that i was just being a commercialish guy and "knocking" another product due to my involvement with audio alloy. none of the above are true, i simply report that bit of information that i have.

i report what information i have, i gave directions to where to find it to verify it yourselves, should you desire to do so.

so perhaps i could offer that the marketing program was so effective that not even test data can undermine it's success. ??

Brian

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
Sponsored Links
Advertisement
 
post #452 of 1328 Old 09-19-2005, 08:40 PM
AVS Club Gold
 
Dennis Erskine's Avatar
 
Join Date: Jul 1999
Location: Near an airport
Posts: 9,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 45
Quote:


It is hard to believe because anything is better than nothing, it would seem

Anytime you put two materials together, you no longer have two materials, you have a composite...a third entirely different material with an entirely different and unique set of properties. Even the order of the layering will make a difference. In many cases putting two layers of something together produces a third item of lesser properties than each individual layer on its own. Not uncommon.

I suspect, had they continued to call it fiberboard (as they did 40+ years ago), they'd never sell it today. Now, by calling it soundboard, they extended the life of the product.

Dennis Erskine CFI, CFII, MEI
Architectural Acoustics
Subject Matter Expert
Certified Home Theater Designer
CEDIA Board of Directors
www.erskine-group.com
www.CinemaForte.net
Dennis Erskine is offline  
post #453 of 1328 Old 09-19-2005, 08:45 PM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by BasementBob View Post


It's not just Brian ... that dislike soundboard.

Very thorough post, but if i could argue nothing more than a semantic point: i don't dislike any product, i just observe that i am not aware of any data from any maker demonstrating full-band gains relative to just adding another layer of drywall.

The california office of noise control offers several sets of test data for soundboard assemblies. over single-wood-stud walls, the STC's range from 36 to 50.

100% of the tests with an STC over 40 in the copy of that test collection

1. have data only down to 125hz
2. have the top layer of drywall only glued in a 6" stripe between the studs to the soundboard below, no screws are used to adhere the drywall to the frame at all

2. can't be built here, not legal
1. raises the question of whether the overall STC was improved at the expense of lower frequencies - because this flexible assembly with no screws lowered the resonance to, say, 100hz from, say, 125 or 160hz.

that's all



Brian

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #454 of 1328 Old 09-19-2005, 09:00 PM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by darkman2003 View Post

Why Why Why !!!

i guess that's why this topic is a sheepish one for me, the potential for contentiousness puts a guy at risk of getting "why why whyd"

if anybody still has further interest i leafed through the CONC's massive mound of test data and found some circa 1966 from the NRC for same-assembly comparisons.

and that, i guess, is about all i can offer. may i someday have better sense than to quote that book in the big GG thread.

That's why i like getting asked about RSIC clips or spring hangers from various makers. They are great products. I promise you that i could walk into any lab in america and demonstrates good performance, superior performance to RC, and good performance/$$$ on many levels.

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #455 of 1328 Old 09-20-2005, 07:38 PM
Senior Member
 
gregavi's Avatar
 
Join Date: Feb 2002
Location: Santa Barbara, Ca
Posts: 311
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Quote:
Originally Posted by Brian Ravnaas View Post

i'd recommend MDF over plywood. For reasons of mass, cost, and flatness.

I can understand mass and flatness, but where are you getting MDF cheaper than plywood?

So, what would be the most effective 2 layer treatment w/GG between. MDF-GG-5/8" SR; 1/2" SR-GG-5/8" SR or... something else? I'm guessing the MDF method is more effective.

It used to be:"Wine, Women and Song"
Now it's: "Beer, The Old Lady and TV"

My Theater Build
http://photobucket.com/GregaviTheater
gregavi is offline  
post #456 of 1328 Old 09-20-2005, 07:48 PM
Senior Member
 
gregavi's Avatar
 
Join Date: Feb 2002
Location: Santa Barbara, Ca
Posts: 311
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Quote:
Originally Posted by Brian Ravnaas View Post

hey maddog,

i agree, it is very nice to put it on when the sheet is on the ground.

I seems this product would be more effective speading it with a notched trowel like mastic. It would have to come in a bucket then. Any thoughts on that Brian?

It used to be:"Wine, Women and Song"
Now it's: "Beer, The Old Lady and TV"

My Theater Build
http://photobucket.com/GregaviTheater
gregavi is offline  
post #457 of 1328 Old 09-20-2005, 08:44 PM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by gregavi View Post

I can understand mass and flatness, but where are you getting MDF cheaper than plywood?

So, what would be the most effective 2 layer treatment w/GG between. MDF-GG-5/8" SR; 1/2" SR-GG-5/8" SR or... something else? I'm guessing the MDF method is more effective.

Home Depot, here in Fargo, in the last 24 months has had MDF cheaper than even OSB at times, routinely cheaper than plywood.


The MDF will perform better because 3/4" MDF is heaver than 1/2" drywall for the other layer. To some extent, mass is it's own reward.


BUT PLEASE UNDERSTAND: there is nothing magical about any common building material. not about MDF. not about plywood. not about cement board. not about anything

You folks can answer this type of question for yourselves in the future by following these basic rules:


-heaver is better
-two damping layers is better than one
-two damping layers at 50% coverage/layer is better than one layer at 100% coverage

Therefore for a given amount of resources, you can always make a list of what's best. I don't think MDF ever makes sense as a choice, because you can always get 2 drywall layers for ~ the same price or less.

drywall/gg/drywall/gg/drywall would outperform mdf/gg/drywall, as it would be heavier, AND itw ould have two damping layers.

make sense?

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #458 of 1328 Old 09-20-2005, 08:47 PM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by gregavi View Post

I seems this product would be more effective speading it with a notched trowel like mastic. It would have to come in a bucket then. Any thoughts on that Brian?

this is a good thread to discuss this.

In theory, troweled application has advantages over tube application, as coverage could reach 100% coverage with a near-perfectly uniform film.


In practice, the walls, frame, boards... are all somewhat bent, warped, and so forth, and the tube application consistently performs fractionally better in tests in our lab.

The nitty gritty of the how's and why's can get chatty, but all tests on GG walls since may have used tube material, and i consider the move to tubes a step in a positive direction for real-world performance with GG.

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #459 of 1328 Old 09-20-2005, 11:24 PM
AVS Special Member
 
BasementBob's Avatar
 
Join Date: Jan 2004
Location: Oakville, Ontario, Canada
Posts: 4,619
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 67
gregavi:

MDF is routinely cheaper than plywood here too, for the same volume.

I wouldn't put MDF as the room side layer -- due to fire.
I wouldn't put MDF as the against the studs layer -- due to fire and moisture.

But if one is putting up 3 layers on one side of the studs, MDF in the middle between gypsum on both sides should be fire safe, and allows things to be screwed to the wall anywhere and hold reasonably strongly. That's the sole reason to do it.

Some isolation (TL) thoughts: MDF is a different density than the drywall, so the coincidence dip should be flatter is a free bonus. Certainly 1/2" to 3/4" MDF is fine, although I might be concerned with 2" (two inch) MDF having a very low coincidence frequency. While green gluing two 3/4" MDF's against each other is good to ok, construction adhesiving two 3/4" MDFs is not.

An amateur built the Ark. Titanic was built by professionals. Of course Noah took a little advice.
BasementBob is online now  
post #460 of 1328 Old 09-21-2005, 08:17 AM
AVS Special Member
 
tlogan6797's Avatar
 
Join Date: Feb 2005
Location: Northern VA
Posts: 4,834
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 36
Quote:


Anytime you put two materials together, you no longer have two materials, you have a composite...a third entirely different material with an entirely different and unique set of properties. Even the order of the layering will make a difference. In many cases putting two layers of something together produces a third item of lesser properties than each individual layer on its own. Not uncommon.

So...maybe I missed it, but what would the recommended order be? Since three of my walls are surrounded by poured concrete....

decoupled stud - 5/8 - gg - 1/2

or

decoupled stud - 1/2 - gg - 5/8


OR

does it not matter as long they are all the same? Would changing the layering on the ceiling from that of the walls provide any benefit, if indeed, the layering matters?

So many questions.....

Tom

Tom Logan
Everytime I reply the thread ends
Need motivation? Get LOGANED
http://www.avsforum.com/avs-vb/showthread.php?t=1014847

An as-yet un-named theater designed by Big-WarrenP-BritInVA
tlogan6797 is offline  
post #461 of 1328 Old 09-21-2005, 10:20 AM
AVS Club Gold
 
Dennis Erskine's Avatar
 
Join Date: Jul 1999
Location: Near an airport
Posts: 9,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 45
Your choices are:

Decoupled stud, 5/8, GG, 1/2
or
Decoupled stud, 5/8, GG, 5/8

You get slightly higher mass with the dual 5/8". Although, my own experience suggested the GG will perform better with the 1/2 outer layer. No data on THIS product to back that up, however.

Dennis Erskine CFI, CFII, MEI
Architectural Acoustics
Subject Matter Expert
Certified Home Theater Designer
CEDIA Board of Directors
www.erskine-group.com
www.CinemaForte.net
Dennis Erskine is offline  
post #462 of 1328 Old 09-22-2005, 05:59 AM
AVS Special Member
 
tlogan6797's Avatar
 
Join Date: Feb 2005
Location: Northern VA
Posts: 4,834
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 36
Dennis -

EXCELLENT! Thanks for the reply. I was leaning in that direction.

Tom

Tom Logan
Everytime I reply the thread ends
Need motivation? Get LOGANED
http://www.avsforum.com/avs-vb/showthread.php?t=1014847

An as-yet un-named theater designed by Big-WarrenP-BritInVA
tlogan6797 is offline  
post #463 of 1328 Old 09-22-2005, 09:46 AM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
i mentioned the other day that i always feel sheepish when i get asked about soundboard, because it might seem like the answer is just me (a guy involved with a product) knocking another product. I guess i don't feel that i've ever given less than the straightest answer i can give to anything. Here's the straightest answer i can give, sheepishness or not.

With respect to soundboard as a product, i'd offer these:

1. it has some sound-absorption properties, like fiberglass. So, if no insulation was to be used, that would be a tangible benefit. As David Harris observed in my quote of him above, that would benefit resilient walls. if no insulation was used. but you'd be out of your skull to build a decoupled wall without using insulation, so the point is moot.

2. it has better internal damping than any other building material. perhaps 10x that of drywall. BUT, the damping of a common wall assembly is many times higher than that of the materials which comprise it due to various odd-ball factors like tiny air leaks behaving cause viscous losses, screws and friction causes losses, etc. So i massively doubt that adding soundboard will have a notable impact on the damping of an actual wall assembly.

3. it has different properties than drywall, and as DE observed above this can have an impact. This will manifest itself basically only at the "coincidence" dip, so you could anticipate that soundboard would improve performance at this problem-region a bit.


Those are the plus's relative to more drywall, here are the negatives

1. it's far less heavy. mass is one of the key components to success in any wall.

So weight -vs- an irrelevant amount of absorption and damping + this different-properties concept.


point worth noting: not all soundboard is the same. the board in the tests run at the NRC 12 years ago that i'll discuss below was 2x as heavy as the board sold around FArgo in 2005. That board - sold around fargo now - is flatly blutly less effective than more drywall on ANY wall.



Let's take a look at the one set of full-band test data that exists in all of the thousands and thousands and thousands of test sets that i have, including dozens and dozens on soundboard assemblies...



the picture "soundboard-vs-drywall" shows these things:

1. the performance of a 2x4 wall with drywall
2. the performance of the same wall with soundboard added to both sides
3. the predicted performance of the same 2x4 wall with drywall added to both sides. This prediction is generated via historical dataq for doubling layers, and there is no test from the NRC for this wall with double layers, hence the need to predict it. it's more than reasonable.


We get about these:

wall STC OITC full-band**
1 layer 41 28 22
soundboard 49 33 27
2 layers 47 32-33 27

** = full band calculation based on Robinson-Dadson equal loudness


And that's the most favorable soundboard test i've seen. The lighter-weight board that Audio Alloy tested recently did no more than just putting some foam tape on the studs, which wasn't much of anything at all - just some mid/high frequency gains. Adding a 2nd layer of drywall to one side would certainly have raised performance by ~ 2-3dB.

so at best, screwing soundboard to the studs will give the same gains as more drywall. at worst, it will yield little improvement at all, and less than just adding drywall.


I've little doubt that on any insulated and decoupled assembly, it will perform worse than drywall. This is because mass affects the frequency at which decoupling becomes effective, and the huge loss in mass will outweigh whatever cavity-size increase effects the semi-porous board has.


so someone said they found it hard to believe that this product is made by so many and sold under the name of sound without merit... i guess i can't offer any argument but: believe.

or put the burden on somebody to prove otherwise. 100% of the high-STC soundboard walls that i've ever seen test data for are

1. reported only down to 125hz
2. use drywall over soundboard glued to the soundboard only in strips between the studs

the effect of that will be to lower the resonance frequency... lower that darn resonance to 100hz from 125 and STC might go up 10 points... doesn't mean the wall is any better. see picture #2


so again, i say that you couldn't demonstrate full-band gains -vs- just adding another layer of drywall. someone said they didn't belive, i say: believe


LL
LL

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #464 of 1328 Old 09-22-2005, 10:06 AM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Limp mass is another example of marketing success in the utter absence of publicized test reports, or even sensible theoretical basis.

STC=27 is awesome for a lil 1/8" sheet of limp-mass material, isn't it?

well, a sheet of 1/2" drywall would typically test to a 27
a sheet of 5/8" drywall might test to a 29
a sheet of 1/4" drywall should test to a 25 or so

you see, folks, the thing about a single sheet of anything is mass. no insulation, no decoupling, resonant behavior VERY MUCH DIFFERENT than a normal wall... mass becomes the most important factor. the advantage of the limp material in this is that the conicidence dip moves to a very high frequency where it doesn't matter at all.



The theory that limp materials are beneficial because they can "move with the soudn and absorb it" is utter nonesense. THE VERY NATURE OF SOUND ISOLATION IS TO PREVENT SOUND FROM MOVING THINGS! THIS IS WHY MASS HELPS, IT'S HARDER FOR SOUND TO MOVE HEAVY THINGS THAN LIGHT THINGS! it is the mass of the limp material providing resistance to motion caused by sound that gives it an STC=27. NOT the limpness allowing motion via sound.



Take that theory to an extreme, and imagine a material so limp that it moved PERFECTLY with the sound. would absorb all of it, right? No, it would transfer all of it, as it would represent no resistance to sound at all.


BUT, no such material can be made. For it is mass that offers resistance to sound, not stiffness. only at incredibly low frequenies or on incredibly small structures does stiffness come into play. not in the audible range or on things the size of walls. Mass is this resistance, not limpness, not stiffness, mass.



These materials originate in the auto industry. where applying them to sheet metal DRAMATICALLY raises the mass of the metal. also, just weighing down the metal can help with resonance problems in the steel - steel is amazingly low in damping.

but that 1lb/square foot... it doesn't add up to much inside a wall that already has a few sheets of 2.2 lb/sq foot and some 1lb/square foot framework. to add 1lb/sq foot of material to a normal 2x4 wall with 5/8" drywall on both sides would give a predicted 1.5 dB due to mass.

you have to make BIG changes in mass to matter, like double the mass of the wall. that would, in theory, give 6dB of gains. in historical lab tests it typically gives 4-5dB.


now, IF (and that's a big if) a limp-mass material was an effective constrained-layer damping material, you could use it in between sheets of drywall. damping can do ALOT for a wall if you add ALOT of damping. if you add a little damping, it's just like adding a little mass, who cares?

but hung limply???? oof creating at iny air cavity somewhere? double oof

the only answer that i can give to someone who would say they don't believe it's so widely recomended is, again, this clever and eloquent response: believe

if anyones test data proves me wrong, i'll paint msyelf pink and sit in the mall for 8 hours. but it won't so i'm safe...

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #465 of 1328 Old 09-22-2005, 10:35 AM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
With respect to the use of Green Glue, and materials to use it in conjunction with:


on floors i recommend OSB. If you like plywood, that's fine, but OSB is cheaper and heavier.


On walls i recommend drywall. Things like OSB and MDF and plywood and soundboard...

They are all less weight-per-dollar than drywall.


5/8" drywall current market price: $9.25
1/2" drywall current market price: $8.05
1/2" soundboard current market price: $8.00
3/4" MDF current market price: $23
3/4" OSB current market price: $23
3/4" AB plywood current market price: $38

5/8" drywall weight per 4x8 sheet: 70lbs
1/2" drywall weight per 4x8 sheet: 56 lbs
1/2" soundboard weight per 4x8 sheet: 20lbs
3/4" MDF weight per 4x8 sheet: 92 lbs
3/4" OSB weight per 4x8 sheet: 77lbs
3/4" AB plywood weight per 4x8 sheet: 71lbs

$$$/pound, 5/8" drywall: $0.13/lb
$$$/pound, 1/2" drywall: $0.14/lb
$$$/pound, 1/2" soundboard: $0.45/lb
$$$/pound, 3/4" MDF: $0.25/lb
$$$/pound, 3/4" OSB: $0.30/lb
$$$/pound, 3/4" plywood: $0.53/lb


Other things to note:

-2 damping layers outperforms 1 damping layer
-2 damping layers at 50% coverage outperforms 1 damping layer at 100% coverage


So, let's assume that we use 50% coverage if we opt for a 3-layer wall, to keep the Green Glue costs the same, we get MORE for our GG that way than with 100% on one layer (albeit not much more)


then we have these options:


3/4" MDF + 5/8" drywall = 162 lbs and $32.25 for board costs
5/8" drywall + 5/8" drywall = 140lbs and $18.50 for board costs
5/8" drywall + 5/8" drywall + 5/8" drywall = 210 lbs and $27.75 for board costs


so we save 5 bucks in total board costs, same price of GG, we gain 50 pounds, and we have 2 damping layers -vs- 1. it's an obvious choice.

use 5/8" + 1/2" + 5/8" and you'll get 196lbs and $26.55 total board cost, still a far better combination


there is never any reason to use anything but drywall in a GG wall. the fire properties of drywall are another plus, as basementbob noted above. installation costs are probably another.


now, a 3rd layer of wall adds alot of installation costs (labor isn't cheap), but sawing wood is probably more expensive labor-wise than score/snapping drywall...




another note: it is preferable to use 2 damping layers with one on each side of the wall than to use 2 damping layers on the same side of the wall.


Brian

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #466 of 1328 Old 09-22-2005, 10:39 AM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
i honestly admire the creativity of everybody with the plans they come up with. Heck, i admire the completely insane sound isolation schemes that sometimes get brought up

a layer of drywall, a layer of soundboard, then 2" of foam, then 3/4" MDF, then resilient channel and R13, then 2 layers of drywall, put heavy felt in the joist cavity, then soundboard under 3/4" plywood....


but, unfortunately for our imaginations, but fortunately for our pocketbooks, the reality of walls and their performance is really pretty simple, and weight per dollar is always a good starting point.


Green Glue will modify the resonant properties (i.e., improve them) more than any possible lamination/combination of different materials under the sun, period.

i support the concept of 5/8" + 1/2" for a GG wall, i flatly don't recommend giving up more mass than that, and i flatly don't recommend deviating from plain old drywall as the material of choice.

hope that helps

Brian

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #467 of 1328 Old 09-22-2005, 10:41 AM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
the only possible case that i can envision for using something other than drywall would be using 3/4" MDF to force some massively non-straight studs to go straight.

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #468 of 1328 Old 09-22-2005, 10:58 AM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
as long as i'm on a lunch-hour posting spree, this might be really interesting for tech-oriented folks out there:


There are 5 basic principles of sound isolation

1. mass (self explanatory)
2. decoupling (resilient channel, RSIC clips, double stud walls)
3. absorption (insulation in a cavity)
4. resonance (see below)
5. conduction (the ability of a structure to transport vibration over distance)

To improve a wall, therefore, you must

1. improve mass
2. add decoupling
3. add absorption
4. reduce or move resonance
5. reduce conduction

4 and 5 are damping controlled. moving resonance is not damping controlled but is a longer story (See later)


This post will cover the bheavior of a single panel, just a wall with no air cavity, no insulation, no studs, just a single boring old panel.



imagine a wall that was just a single panel. ok? like just a 4" concrete slab, or a sheet of 5/8" drywall supported only at it's edges with no studs.


when sound hits this single panel, it tries to vibrate it. Mass offers resistance to vibration, the heavier the panel, the less effectively sound can vibrate it. that is the first principle - mass - coming into play.

the 4th principle - resonance - also comes into play. AT resonant points of the panel, it becomes extremely easy for sound to vibrate it regardless of mass.


So for a single panel, you have a fairly simple situation of mass minus resonance. Mass defines the potential, resonance takes away from that potential at various frequencies.



in the attached pic you can see the potential offered by the mass of 3 different partitions compared to the actual results.

resonance causes the concrete to fall well below it's potential, this is the coincidence dip.

resonance causes the drywall to fall below it's potential as well, but only at very high frequencies, this is also the coincidence dip.

the plywood suffers much more severe resonance problems than the drywall because it is firmly screwed to floor joists, rather than floating on resilient channel. the stiffness of the installation causes additional resonances outside of the coincidence problem.


to improve these partitions without adding an air cavity, you have only two options:

1. add mass
2. add damping, to mitigate the resonance problems



so that's single panels in a nutshell


next post: talk about how a decoupled wall works!
LL

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #469 of 1328 Old 09-22-2005, 11:29 AM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
now imagine a decoupled wall, let's just take a double wood stud wall for one example


the same thing that happens to a single panel happens here - sound hits the drywall on one side of the wall, and vibrates it. the resistance to vibration is JUST LIKE ABOVE, mass -minus- resonance


however, because the two sides of the wall aren't physicall connected, the vibration can't immediately transfer to the other side. pretty straightforward, that.

The thing about decoupling that many people don't grasp, is that the air in the cavity (and the force of the resilient channel in an RC wall or the force of an RSIC clip in an RSIC wall) behaves like a spring.


And with this spring force, and the mass on either side of the wall, you get a new resonance, called a mass-spring resonance. 3 frequency ranges are thusly created:

1. At this resonance point, the performance of the wall won't be so good, it will be WORSE than if you hadn't decoupled the wall

2. well below this resonance point, the performance of the wall will be the same as if no decoupling were present. At very low frequencies, performance will be THE SAME as if you hadn't decoupled the wall

3. well above this resonance point, performance will improve DRAMATICALLY. well above this resonance point, no other method is as effective at improving the performance of a wall as decoupling.


so, this mass-spring interaction results in this situation:

1. sound shakes the inner mass
2. around the resonance, the spring behavior amplifies this vibration, and MORE vibration occurs on the other side
3. well above the resonance, the vibration cannot transfer and performance soars






The attached pic shows this:

1. at very low frequencies the air + resilient channel behaves as a "stiff" mass

2. at the resonance point performance suffers considerable

3. well above the resonance point performance soars



so it is obvious from this assessment that the most important thing we can possibly do for a decoupled wall is lower the resonance frequency. This lowers the weak-spot to a frequency that's less offensive (it's harder to hear 30hz than 60hz), and it moves the frequency where the wall starts to get really, really good down.


These rules

1. use as much mass as possible on both sides of the wall
2. use as deep an air cavity as possible
3. use insulation
4. don't use resilient channel

will always help you steer the resonance point down in frequency. resilient channel has too strong a spring force, and keeps the resonance much higher in frequency than other methods, making it a worse performer below the STC frequency range (STC only goes to 125hz)



The graph below outlines this perfectly. The enormous gains at mid/high frequencies caused by the combination of decoupling + absorption are so immense, that you would have to utilize literally 40-60+ layers of drywall to match them.

But, at low frequencies, the resonance makes it WORSE than no decoupling.

I spliced some NRC data into this graph as they have a higher-limit-facility and to use the AUdio Alloy data would short-change the actual gains wrough by decoupling. I used Audio Alloy/Orfield low freq data as all that data is same lab/same time, and makes for a better comparison.

The overall gains due to decoupling sort of flatten out at mid/high frequencies for a couple of reasons

1. sound transferring through the channel, or through other slight structural connections
2. sound making it through the air / limitations of absorption in the cavity


So that's the awesomely potent, but sometimes risky, second principle of sound isolation - decoupling. awesome in potency well above it's resonance, risky because if you plop that resonance at a problematic frequency, you'll find yourself scratching your head and wondering why your uber-high STC wall still lets hoards of bass through.



And that's as good of a summary of how decouling works as you'll find anywhere, provided i explained it clear enough to make sense.
LL

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #470 of 1328 Old 09-22-2005, 12:13 PM
AVS Club Gold
 
GetGray's Avatar
 
Join Date: Aug 2004
Location: Mid-South USA
Posts: 5,426
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked: 46
Quote:
Originally Posted by Brian Ravnaas View Post

Said A lot

So don't use RC? I'm confused. What about RC mounted on RISC clips?

The more I read on this topic, the less I know. If I buy some green glue can I get some personal help/advise on from you on my wall systems? That is, what is best for my isolation goals?

I'm re-doing my basement and have about 3 different wall assemblies to deal with.

Mainly:

1) belowground wall:
earth->10" reinforced poured concrete -> [unfinished my choice of studwall or other assembly]

2) existing exterior wall
Brick->air->1/2" foamboard- 2x6 stud with high density fiberglass insul->existing 1/2" drywall[->second wall system acceptable since I have about 12" of wall system #1 at the bottom.]

3) A smaller amount of exisitn standard 2x4 stud assemblies with 1/2" drywall on each side.
I can add an assembly in front of the existig one. I cannot easily add more drywall layers to the other side. It's my understanding from other threads in this particualr case, it would be better to remove at least the drywall from the inner sice before building a new (decoupled) wall assembly. Yes?

4) The worst assembly, I've yet to decide what to do with:
upstairs living space -> [upstairs flooring: thick carpet+pad | 1/2 ply+vinyl | 3/4 hardwood] -> 20" 2x4 type web trusses -> future HT ceiling.

In this last case, I'm concerned about that truss space. It contains a lot of air to resonate, plus the upstairs HVAC vents. Filling it with insulation would be incredibly expensive (20" depth, 540ft^2) but mostly it's very difficult to do since the fiberglass woudl need to be cut to fit each truss web component., then the space between teh trussed could be filled.

Other options are to blow it full of cellulose (I have no idea what that woudl do to the properties) or to do a combination of blown and spreay on icenye (sp?) foam agains the floor.

Then, once the cavity is filled (or not?), what materials to use as the final wall layer.

Suggestions?

Thanks, Scott
GetGray is offline  
post #471 of 1328 Old 09-22-2005, 01:01 PM
AVS Special Member
 
BasementBob's Avatar
 
Join Date: Jan 2004
Location: Oakville, Ontario, Canada
Posts: 4,619
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 67
Brian:

Nice effectofdecoupling.gif

The bottom line of that is similar to

from: http://www.earsc.com/HOME/engineerin...dex.asp?SID=61

But yours is about walls, so the curve is a little different.

An amateur built the Ark. Titanic was built by professionals. Of course Noah took a little advice.
BasementBob is online now  
post #472 of 1328 Old 09-22-2005, 01:49 PM
AVS Special Member
 
BasementBob's Avatar
 
Join Date: Jan 2004
Location: Oakville, Ontario, Canada
Posts: 4,619
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 67
GetGrey:

Quote:
So don't use RC? I'm confused. What about RC mounted on RISC clips?

Skip the RC.
If you have double stud walls or other decoupling, then you don't need RSIC.
RSIC with hat channel is normal, RSIC with RC is never done.

An amateur built the Ark. Titanic was built by professionals. Of course Noah took a little advice.
BasementBob is online now  
post #473 of 1328 Old 09-22-2005, 01:50 PM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by BasementBob View Post

Brian:

Nice effectofdecoupling.gif

The bottom line of that is similar to

from: http://www.earsc.com/HOME/engineerin...dex.asp?SID=61

But yours is about walls, so the curve is a little different.

yep, EXACTLY the same thing, exact same principle at work. they just show transmissisiblity, with the resonance up and the good stuff down, and mine was reversed, flipped upside down.

thanks, BTW

Brian

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #474 of 1328 Old 09-22-2005, 02:00 PM
AVS Club Gold
 
GetGray's Avatar
 
Join Date: Aug 2004
Location: Mid-South USA
Posts: 5,426
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked: 46
Quote:
Originally Posted by BasementBob View Post

GetGrey:


Skip the RC.
If you have double stud walls or other decoupling, then you don't need RSIC.
RSIC with hat channel is normal, RSIC with RC is never done.

Thanks BasementBOb: I had a fundamental misunderstanding. I thought the hatchannel that attached to the RISC clips was RC.

That cleared up, then what about my problem assembly, the truss floor (ceiling) system? Use RISC (and hat channel) on it?

So for the other walls, if I do not have them decoupled via a double wall or staggered stud, *then* use RISC, but if they are decoupled, don't?

I thought Brian was just saying to not decouple the things for LF (where I'm most worried)?
GetGray is offline  
post #475 of 1328 Old 09-22-2005, 02:08 PM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by GetGray View Post

So don't use RC? I'm confused. What about RC mounted on RISC clips?

The more I read on this topic, the less I know. If I buy some green glue can I get some personal help/advise on from you on my wall systems? That is, what is best for my isolation goals?

I'm re-doing my basement and have about 3 different wall assemblies to deal with.

Mainly:

1) belowground wall:
earth->10" reinforced poured concrete -> [unfinished my choice of studwall or other assembly]

2) existing exterior wall
Brick->air->1/2" foamboard- 2x6 stud with high density fiberglass insul->existing 1/2" drywall[->second wall system acceptable since I have about 12" of wall system #1 at the bottom.]

3) A smaller amount of exisitn standard 2x4 stud assemblies with 1/2" drywall on each side.
I can add an assembly in front of the existig one. I cannot easily add more drywall layers to the other side. It's my understanding from other threads in this particualr case, it would be better to remove at least the drywall from the inner sice before building a new (decoupled) wall assembly. Yes?

yes, remove the drywall from the inside before building a new stud row, makes for a much larger air cavity = lower effective frequency of decoupling. A generally better resonant behavior as well.

Quote:
4) The worst assembly, I've yet to decide what to do with:
upstairs living space -> [upstairs flooring: thick carpet+pad | 1/2 ply+vinyl | 3/4 hardwood] -> 20" 2x4 type web trusses -> future HT ceiling.

In this last case, I'm concerned about that truss space. It contains a lot of air to resonate, plus the upstairs HVAC vents. Filling it with insulation would be incredibly expensive (20" depth, 540ft^2) but mostly it's very difficult to do since the fiberglass woudl need to be cut to fit each truss web component., then the space between teh trussed could be filled.

don't fret about filling the whole space, it won't hurt, but using R19 fiberglass isn't so expensive, and will offer alot of performance. I can dig up some NRC data on changing insulation thickness if you like.

Quote:
Other options are to blow it full of cellulose (I have no idea what that woudl do to the properties) or to do a combination of blown and spreay on icenye (sp?) foam agains the floor.

Then, once the cavity is filled (or not?), what materials to use as the final wall layer.

Suggestions?

Thanks, Scott

skip the isocyanate/urethane/expanding foam unless it's specifically stated to be open cell and acoustic. a 20" joist cavity is a good thing, not a liability. I recommend using decoupling and 2 layers of drywall. Don't use resilient channel or untested sound clips.


The weakest link in your exterior wall assembly is the foamboard on the back of the studs. I suppose that's there for some purpose that makes it not good to remove it... use double drywall on the front of those studs - is that in your plans?

a double-stud wall where the 2x4 wall is now (remove one layer of drywall, add double drywall on a new set of studs) is a great idea.

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #476 of 1328 Old 09-22-2005, 02:11 PM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Quote:
Originally Posted by GetGray View Post

Thanks BasementBOb: I had a fundamental misunderstanding. I thought the hatchannel that attached to the RISC clips was RC.

That cleared up, then what about my problem assembly, the truss floor (ceiling) system? Use RISC (and hat channel) on it?

So for the other walls, if I do not have them decoupled via a double wall or staggered stud, *then* use RISC, but if they are decoupled, don't?

I thought Brian was just saying to not decouple the things for LF (where I'm most worried)?

all decoupled assemblies will have this problem area at low frequencies somewhere if they are not heavily damped. Damping can help with the low-frequency resonance and help the mid/high frequencies too (at other resonant points in the assembly). The effect of damping varies from system to system.

when building a decoupled assembly, you can do this AND get good low-freq isolation, you just have to take care to follow the guidelines that i offered above and make sure that the resonance point of the system is as low as possible. see?

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #477 of 1328 Old 09-22-2005, 02:12 PM
AVS Special Member
 
BasementBob's Avatar
 
Join Date: Jan 2004
Location: Oakville, Ontario, Canada
Posts: 4,619
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 67
GetGray:

Quote:
I thought Brian was just saying to not decouple the things for LF (where I'm most worried)?

Decoupling increases the amplitude of the wall system mass-spring-mass resonance (often between 20hz and 100hz), becuase there's a little less structural damping.
Green Glue reduces the amplitude of both the wall system mass-spring-mass resonance, and the coincidence dip.
More mass, and larger cavity, may lower the resonance frequency below what your subwoofer generates. Getting it about an octave lower would be perfect.
Double Stud Wall style decoupling maximizes the mid to high frequency isolation, and when combined with green glue should give a pretty darn good wall for Home Theatre.

Quote:
So for the other walls, if I do not have them decoupled via a double wall or staggered stud, *then* use RISC, but if they are decoupled, don't?

Yep. (Please try to use positive logic, rather than multiple negatives)

Quote:
That cleared up, then what about my problem assembly, the truss floor (ceiling) system? Use RISC (and hat channel) on it?

There are three solutions for ceilings
a) ignore soundproofing, and use the space between the joists for acoustic treatment
b) if your ceiling can take the weight (professional advice required -- don't read joist span tables yourself for this IMO), use RSIC and a couple of layers of drywall with green glue
c) put more joists in a room-in-a-room style. These would be decoupled, so no RSIC, and dead-load calculations are DIY readable from joist span tables. Ted White has an example on his website.

An amateur built the Ark. Titanic was built by professionals. Of course Noah took a little advice.
BasementBob is online now  
post #478 of 1328 Old 09-22-2005, 02:54 PM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
the third principle of sound isolation is absorption.

Sound absorbing materials, like fiberglass or mineral fiber, can so some nice things for a wall or floor/ceiling. The basic positive effects of insulation, in order of importance, are

1. lowers the mass-spring resonance frequency in decoupled walls. In essence, this means that the decoupling is effective to a lower frequency

2. absorbs airborne sound passing through the cavity

3. eliminates resonances in the air cavity. This isn't the big low-frequency resonance, these are middle and high frequency resonances that occur like room modes inside the wall

4. damps the low-frequency mass-spring resonance. historical data suggests this is perhaps a dB or two at most.


Insulation is most effective in decoupled walls. This is because there isn't a direct mechanical path, and sound has to go through the air cavity to reach the other side. In a coupled wall, like a common single-stud 2x4 wall with the drywall screwed directly to the studs, sound can easily transfer without going through the air cavity, effectively bypassing the insulation.

The first two attached pics outline this drastic change in effectiveness from a coupled to a decoupled wall.


WHAT TYPE OF INSULATION IS BEST?

Plain-jane boring old fiberglass is best. I know you've been hit with 1000 degrees of "denser-insulation-is-better", but like soundboard above, this is the result of decades of greusomely effective marketing by massive companies. Actual existing data does not support the assertion.

Taking the 350+ walls tested in IR-761 and IR-693 by the NRC in Canada, we find that plain old fiberglass yields the highest STC in the overwhelming majority of wall categories if not all. How can this be???


-denser insulation, like mineral fiber or cellulose, is a superior absorber. They generally yielded improved middle and high frequency performance.

-normal fiberglass is superior at lowering the mass-spring resonance of the walls, so they generally yielded preferable low frequency performance and higher STC's.



None of these materials can "absorb" 50hz. Try it at home - put a 3" thick piece of insulation in front of your mid/treble speakers. it'll destroy the sound. put it in front of your sub. it won't do anything much at all. They improve low frequency performance by lowering the frequency of mass-spring resonance, and this is by far the most important contribution they make to a wall.

That doesn't mean that mineral fiber is worse, it simply means that it shouldn't be considered better.

You should avoid wasting money on specialty high-density glass or mineral fiber in wall cavities. Just use regular fiberglass. If anybody vehemently protests, please send them to this thread to debate it.





Then the question comes up, do i need to fill the entire cavity? Historical test data suggests that the answer is no. It doesn't hurt to fill the entire cavity, but there is not reason to believe that leaving any empty space will cause problems.

In one big study - IR811 by the NRC - they found that using R9 insulation made a large improvement over no insulation. And slight incremental improvements moving from R9 to R13 to R19 to R25. But going from nothing to somethign, from nothing to R9 was by far the biggest improvement, by far.

They over-stuffed the joist cavities in that same test set slightly, but putting 270mm fiberglass into a 2x10 joist cavity, performance did not suffer.

important note: this canadien study used resilient channel on the ceiling. the impact on low-frequency behavior via location of mass-spring resonance is masked by that. The channel is stiffer than the air in a 2x10 joist cavity, and so reducing the stiffness of the air cavity has a relatively very faint effect. make sense?

In 1983, using denser Thermafiber, USG found that over-stuffing slightly a resilient channel wall's cavity had a detrimental effect at high frequencies.


So to sum, the most important thing is that you use some insulation. Things like density and do i fully stuff or half-stuff a ceiling cavity aren't going to be the make-or-break points.
LL
LL

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #479 of 1328 Old 09-22-2005, 03:03 PM
AVS Special Member
 
Brian Ravnaas's Avatar
 
Join Date: Jun 2004
Posts: 2,136
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
stuffing cavities is ok, overstuffing cavities is ok, some benefit will come from more absorbing material.

but i would never, if in a financial pinch, appropriate resources to more insulation before more mass. Or to more insulation before other means or techniques.


For example, a resilient channel ceiling with 10" of insulation won't outperform an RSIC ceiling with R13.

With 20" joist cavities, using R13 or R19 and double drywall will do more than using 20" of insulation and single drywall.

If building a double stud wall, you'd be far better off to use 50% GG between the double drywlal on one side with single R13 than to use double R13 and standard drywall...

etc. Insulation is critically important, no serious sound partition should ever be without it.

But don't break the bank on fluffy stuff and mineral fiber. Use how much you can, and don't bother with expensive types at all unless test data exists to show they are more effective at lowering the mass-spring resonance frequency.

Understanding sound isolation
That link may be helpful
Brian
Posted content copyright 2004-2008 Green Glue Company, LLC
Brian Ravnaas is offline  
post #480 of 1328 Old 09-22-2005, 03:18 PM
AVS Club Gold
 
GetGray's Avatar
 
Join Date: Aug 2004
Location: Mid-South USA
Posts: 5,426
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 20 Post(s)
Liked: 46
Brain and Basement Bob:

Thanks:
Quote:
> " skip the isocyanate/urethane/expanding foam unless it's specifically stated to be open cell and acoustic. "

Well, *they* say it is, but I see no data to justify it. I't open cell, but has a closed "skin" after installation if that matters any. In normal stud walls they cut the excess flush which exposes the cell structure. Here's a pdf with details and some STC data. Maybe you could take a look? One nice thing about it, it *does* fill every tiny hole, gap and crevice.
Quote:
> "a 20" joist cavity is a good thing, not a liability. I recommend using decoupling and 2 layers of drywall. Don't use resilient channel or untested sound clips. "

A good thing even without filling it with insulation? That extra airspace wont turn into a "drum"?Are RISC "tested", that was my planned clip since it was apparantly popular here.?
Quote:
> "The weakest link in your exterior wall assembly is the foamboard on the back of the studs. I suppose that's there for some purpose that makes it not good to remove it... use double drywall on the front of those studs - is that in your plans?"

Yes, that was my plan, remove the existing drywall, build decoupled inner wall and fill extra cavity with insul. I have vapor barrier issues to deal with on that wall however and those are not to be treated lightly lest one end up with mold growth. 10" of insulation might be a bit much to dry to outside. I may leave the existing vapor barrier in place and build to allow air circulation through the "extra" wall. The foam board on the exterior wall as described is standard residential construction around here (TN). No way to change that layer.
Quote:
> when building a decoupled assembly, you can do this AND get good low-freq isolation, you just have to take care to follow the guidelines that i offered above and make sure that the resonance point of the system is as low as possible. see? "

Well, not exactly. I mean I get the rules you posted, but I'm not sure how to know if my resonant point is low enough. Will "5/8" + 1/2" for a GG wall" do it? Remembering I can't really treat the other (outer) side of any of my assemblies. I can add studs with insulation, and wall covering (drywall layers). They can all be decoupled. Bob:
Quote:
>Yep. (Please try to use positive logic, rather than multiple negatives)

Sorry, I saw I had done that after posting. Let me restate to be sure I understand:

- Wall not decoupled, use RISC to mount drywall
- Wall decoupled, RISC adds no benefit and should not be used

Right?

And as a followup, Are RISC good to use FoR decoupling a stud wall assembly from the adjoining wall?
Quote:
>There are three solutions for ceilings
> a) ignore soundproofing, and use the space between the joists for acoustic treatment

I'd rather have the soundproofing I think. But I have not ruled out giving up since I have other places to deal with stopping the sound. No sense doing heroic wall assemblied with leaking HVAC and doors.
Quote:
> b) if your ceiling can take the weight (professional advice required -- don't read joist span tables yourself for this IMO), use RSIC and a couple of layers of drywall with green glue

I'll check but I'm pretty sure it can handle it. I had the tursses built to over commercial standards (50lbs LL, L/480 deflection IIRC, I'll have to lookup my engineering drawings on the floor truss specs.) Always good to be sure.
Quote:
> c) put more joists in a room-in-a-room style. These would be decoupled, so no RSIC, and dead-load calculations are DIY readable from joist span tables.

I've looked into this. Due to the mechanicals interleaved into the trusses and the long spans, I'd have to drop the joist enough to whack off at least 9" overall room height vs clips. It's at 9' now, hate to go lower.

Thanks as always for the input guys.
Scott
GetGray is offline  
Reply Dedicated Theater Design & Construction

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off