Inner wall insulation + TV (1 Viewer)

[JohnVee]

I'm tearing down my hall bathroom to the studs and joists. It's roughly 5'dx8'wx8'h and the long wall adjoins my master bath (same dimensions). The showers and sinks are the reverse of each other; toilets are offset by one joist bay. This puts the hall tub and the master sink along a master bedroom wall. House built in 1970.

I grew up in a similar house (same era, different state) and seem to recall that there wasn't much noise being transmitted from one room to the other, either room to room or room to bath.

What are my options for cutting down on noise transmission? Is it as simple as insulation? If so, what type? I know I can double up on the drywall, but I can't do that around tub-level due to size constraints (tub fits flush to studs) - I'm concerned about the tub acting as a resonator when a visitor decides to drop a deuce while I'm one wall away trying to go to sleep/not ready to wake up yet.

Also, this is the only bathroom in the house with a tub. My wife has requested a TV that can be seen from the tub. That will place it on the long wall over the toilet. Is there anything I need to be concerned about regarding humidity? The fan she gave me to install is 70cfm and 1.5 sone, so it's almost twice the CFM as the space should require. Honestly, we have guests maybe 10 nights per year and we use the tub another 12-15 times per year...pretty infrequent.

Thanks for any info and advice.

 

[snobdds]

Rock wool insulation. Then cement board and a water barrier.

Fan should vent to the roof to expel humidity. That means a hole in the roof with proper flanges and vent and ducking.

Do it right from the get go. Don't get penny wise and pound foolish.

 

[doug720]

Sound is vibration, adding wall cavity insulation has minimum affect on sound transmission through walls.

To limit sound transmission, you need to isolate the the wall finishes - drywall, tile. etc from the framing. This is done in several ways.

Resilient channel under the wall finish

Staggered stud walls

Dual walls,

Etc.

Look up STC ratings and follow what ever detail works for your situation and budget.

 

[45Kevin]

Sound is vibration, adding wall cavity insulation has minimum affect on sound transmission through walls.

Almost totally false. Adding batt insulation reduces sound transmission through the air cavity. This is your best bang for the buck noise reduction in this case.

To limit sound transmission, you need to isolate the the wall finishes - drywall, tile. etc from the framing. This is done in several ways.

Resilient channel under the wall finish Probably not feasible given space constraints

Staggered stud walls see above

Dual walls, see above

Etc.

Look up STC ratings and follow what ever detail works for your situation and budget.

To reduce resonance from the tub (I'm assuming a steel or fibre-glass tub), embed it in a lump of concrete. Alternately, though not as effective, spray a can of low expansion foam under it once it is firmly installed.

Not sure about the humidity affecting the TV, but put adequate support backing in before putting the wall board up.

A link to everything you need to know about sound transmission mitigation.

http://www.usg.com/content/dam/USG_...hed_assets/acoustical-assemblies-en-SA200.pdf

 

[KLF]

Roxul (rock wool) is a good idea, we use that in party walls in duplexes (also for fire protection), but you also need an acoustical absorbing device. Sound channel is the easiest, double-studding is most effective but takes more room.

 

[doug720]

Here are STC rated wall assemblies and their construction and effectiveness in limit sound transmission. If you have coupled wall construction, filling the cavity has some affect on sound transmission, but the higher STC ratings are achieved with other means.

A non-coupled wall will benefit from from cavity insulation, but adding RC/clips/isolation will help even more.

We build STC rated and inspected walls on a regular basis that must pass sound transmission tests.

The best sound ratings with a coupled wall built with single wood 2x studs and plates and 2 single layers of drywall are achieved with RC/clips with loose fill insulation.



4 Elements of Soundproofing

How exactly do you build a soundproof room? Start with a basic understanding of soundproofing construction. If you understand the basics, you’ll have a more educated eye to view your problem room. In general, we are trying to stop vibrations from getting to “your” side of the wall or ceiling.

Below is an illustration of the typical noise problem through a typical wall. He’s making noise on his side of this wall, and you hear it.



The red arrows in the above diagram demonstrate how sound is conducted from his side to your side. Rigid drywall is rigidly connected to the wall studs, which are rigidly connected to your drywall. The vibration conducts straight through.

The blue waves indicate airborne transmission. His drywall is vibrating back and forth which produces a sound wave in the air cavity. This, in turn, vibrates your drywall and recreates the sound on your side. The drywall becomes a giant diaphragm and acts exactly like your stereo speaker moving back and forth re-creating recorded sound from your favorite CD.

Let’s briefly look at the 4 basic elements of a well-isolated room.

1. Decoupling
The first element is decoupling. Keep in mind that sound is nothing more than a vibration. The vibration will travel (conduct) easily if there is a nice solid direct pathway to follow, like the string between two orange juice cans. If we cut the string, however, we “decouple” the pathway, and the sound vibration stops (no conduction).



Obviously for soundproofing, we want less sound vibration to travel from one side of the wall to the other. It is therefore enormously beneficial if we decouple the framing in our walls (and ceilings). It’s simple, inexpensive and highly effective. Let’s look at different methods of decoupling:

• Double Stud Wall with Green Glue
• Soundproofing Clips with Green Glue
• Staggered Stud wall with Green Glue
• Resilient Channel with Green Glue

You can see that all of these methods offer varying degrees of separation of the drywall on one side from the drywall on the other side. Again, all of the walls shown are superior to a single stud (common) wall.



We can see how decoupling the wall studs limits the vibration trying to conduct through the wall. We are left with the airborne transmission represented by the blue waves. Note how decoupling does not affect airborne transmission.

So our decoupled framing reduces a good deal of vibration, but not all. We need to continue to the other elements to reduce more.

2. Absorption
Air cavities will resonate. Ever “heard the ocean” in a seashell? Ever blow across the top of a bottle and heard the sound? Both sounds are actually the trapped air resonating. A hollow wall will also trap air that will resonate. When the wall is vibrated by sound (from your neighbor), the air in the wall cavity is also vibrated, just like a drum. This air cavity is another means for sound vibration to travel from one side of the wall to the other.



As you can see, even though the wall framing is decoupled, the vibrating air cavity will still transmit some sound through the wall between the wall studs. Simple fiberglass insulation will absorb some of this (absorption).

Insulation helps, and should be done if possible, but the vibration reduction is smaller than the other 3 Elements. You can use other insulation materials as well like cellulose, mineral wool, and recycled cotton. The key is to keep the density low. Don’t compress or pack the insulation.

So now we have a de-coupled and insulated wall framing. These elements stop much vibration, but not all. What do we do now?

3. Add Mass
A very important element. In this case, we simply mean make the walls as heavy as you can. Common cost effective choices for heavy materials include Drywall, Plywood, OSB, and Cement Board.

For sound to conduct through a wall, it has to actually move the wall ever so slightly . A heavy wall is harder to move than a lighter wall. Simple as that. Drywall is one of the lowest cost sources of mass available. Best to use two layers of 5/8″ drywall. It is very important to note that a heavy wall will still vibrate, just not as easily.

Note that adding mass improved things. It’s harder for sound to move this heavier wall. You will still hear low frequencies (bass) quite easily.

Simply adding more drywall does not get you a lot improvement in the low-frequency bass.

• Two Sheet of Drywall OL 05-1057
• Three Sheets of Drywall OL 05-1058
• 
  Four Sheets of Drywall OL 05-1059

This graph illustrates the performance gains from adding additional drywall. While adding mass obviously helps, it doesn’t help as much as we need.

So we have a wall that is decoupled, has some insulation and is heavy. Stops much vibration but still not all. Is there anything else we can do to reduce vibration?

4. Damping
The last element for soundproofing. If we could reduce the drywall from vibrating in the first place, it would make the jobs of the mass, the insulation and the decoupling easier and much more effective. After all standard drywall is a HUGE surface area that is vibrating.



Note how damping the drywall on the sound producing side of the wall reduced all vibration immediately. Again, the decoupling, absorption and mass all have less of a job to do, resulting in significantly improved performance.

 

[45Kevin]

Great stuff Doug, but I don't think it is applicable in this case. You need 60" for standard tub and thickening the wet wall would require moving the toilet flange. Maybe that is easy though. Same on the door wall, you would need a custom jamb.

If it not too much trouble, installing a solid core door will reduce sound transmission as well.

There is a brand called Safe-n Sound (something like that) that HD or Lowes will carry at a reasonable price, in several styles.

John, my wife likes to watch TV from the tub as well. I put a two sided fireplace between the master bedroom and the ensuite. We placed the bedroom TV so that you can watch it through the fireplace while laying in the bath. It gets used almost daily. Happy wife, happy life.

 

[JohnVee]

Thanks for the info, guys. Doug's post is quite informative.

This project is getting slowed down now due to the tree (neighbors') that fell on my house last week. I might not get to do anything other than insulation so I can still meet my deadline.

 

[Asqrd]

We picked up an 'insulated' tub at Home Depot a few months ago and it's all but eliminated the normal shower drip noises we used to get. It wasn't much more than a standard tub either.

 

[LazyL]

I used quiet rock dry wall with insulation between walls used their silicone on sjtuds an wrapped electrical boxes with their putty