Roxul Safe n Sound or Pink Quiet Zone

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Brand (like produced by a certain company) should be of no significance.

A question is what you want to achieve. Is it acoustic treatment inside your room, to make it sound more pleasant when playing music? Is it insulation to more easiliy keep a certain temperature in it? Is it isolation, to avoid disturbing rooms nearby or neighbors (and keep out noise from outside.)

Depending on native language, there are often misunderstandings what is meant when someone writes insulation / isolation.
 
If attempting to isolate a loud HT setup ( from the rest of the family living quarters then I recommend that you buy something like this book ( for a good reality check );

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Home-Recording-Studio-"Build-It-Like-The-Pros"

It'll give you an idea what it takes to accomplish some meaningful sound isolation within a building ( for either home studio or HT ).

If your goal is strictly to insulate from the cold then buy the type of insulation with the best R-factor per $$ .

:)
 
Brand (like produced by a certain company) should be of no significance.

A question is what you want to achieve. Is it acoustic treatment inside your room, to make it sound more pleasant when playing music? Is it insulation to more easiliy keep a certain temperature in it? Is it isolation, to avoid disturbing rooms nearby or neighbors (and keep out noise from outside.)

Depending on native language, there are often misunderstandings what is meant when someone writes insulation / isolation.

well I want to use it for isolation inside the outerwalls.
But some others have also mentioned the fact that the roxul insulation will not promote mold growth if wet which is really great too... but man its expensive.
 
That video is an acoustics disaster. There is so much wrong with it and I'm very concerned that it already has 500k views.

BAD
1) He confuses STC with NR (not to be confused with NRC). STC 40 just describes the construction of the wall itself. STC doesn't take into account the finishes/sizes of the adjoining rooms or, more importantly, the many possible flanking pathways. Telling someone to shoot for STC 40 to get these certain results will lead people to believe that an STC 40 wall construction will get them to where they want to be. In reality, it's the flanking pathways that are more important.

REALLY BAD
2) He says that noise will travel through ducts, which is true, and that there's nothing you can do to stop it, which is false, and that you have to switch to in-floor heating. This is a terrible recommendation. Adding lined duct is way cheaper and easier than switching the way your house is heated.

REALLY BAD
3) He explains the action of resilient channel as creating little waves with its holes that cancel sound out. As if it were equivalent to active noise cancellation. That is ABSOLUTELY BONKERS. I've heard a ton of crazy amateur theories on acoustics in my career and this may actually top the list. RC works by decoupling the gypboard from the studs/joists so that less sound travels through as vibration. There are alternatives to RC that work the same way and have no holes. I really want to know where he heard this.

GOOD
4) Claims that the reason insulation works is that it's so dense that sound has difficulty getting through it. This is sort of true. Then he talks about the "STC ratings for mineral wool." There is no such thing. But he follows that by saying that mineral wool doesn't perform much better than fiberglass. THIS IS TRUE (see my previous comment).

BAD
5) Claims that Type X wallboard is somehow extra dense. It's not. If anything, it's a little less dense than regular drywall.

BAD
6) Claims that Green Glue "creates a tiny air space" between layers of drywall. Untrue. Green Glue has a similar effect to RC in that it creates a decoupling that reduces vibration transmission.

BAD/GOOD
7) Green Glue between 2 layers of 5/8 is not necessarily a better solution than adding batt insulation. I'm sure that going this route will "save you a fortune." Later in the video he claims that Green Glue increases STC by 5 points. I think that's probably true, but I also know that adding batt insulation has the same effect.

BAD
8) Having 1-1/4" plywood under your flooring does not give you great soundproofing. It helps with airborne transmission a bit, but does basically nothing for footfall noise, which is the biggest concern with floor-ceiling systems.

GOOD/BAD
9) He says that joints should be staggered. Very true. But you also need to tape/seal both layers to get the best performance.

BAD
10) There is a difference between floors and ceilings, and it's not all about STC. In a floor/ceiling system, IIC (impact isolation class) is very important, too. Possibly more important than STC.

VERY BAD
11) His "decoupled" double-stud wall has several things wrong with it. 2 stud rows is a great arrangement, but he's doing it wrong and he ends up reducing its effectiveness.

- He has 2 separate stud rows but still staggers his studs. There's no reason for this. There's another stud arrangement called "staggered stud", but in that system the studs share a 6" base plate, so it's necessary. If each row has its own plate, there's no reason to stagger them.
- This wall would be more effective if that internal layer of drywall that he attaches to the first stud row was moved so that it creates a double layer on the new stud row. A wider air cavity between layers of drywall increases the isolation for lower frequencies, which is very helpful for the Star Wars situation he keeps talking about.
- The electrical problem wouldn't exist if he didn't install the internal layer of drywall.

BAD
12) A small gap can make a big difference. He absolutely should worry about the gap near the outlet. He should also be taping and floating every layer.

BAD
13) Resilient channel will add A LOT more than an extra point or two.
 
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