We’re having a home built and I’m trying to find an interior-wall sound deadening insulation that is safe. We were going to use Roxul AFB (acoustical fire bats) but it looks as if they use formaldehyde in its manufacture. Also, it’s got the same issues as traditional fiberglass with regard to itching, need to wear respirators, etc.
Most materials that would readily harbor mold and vermin are chemically treated to prevent both, and cellulose blown-in insulation is apparently treated heavily with borax to make it flame retardant.
We are planning to sound-deaden everywhere so I want to use something that won’t settle or cause health issues over time.
Any ideas? If so, then the next question is availability. The house is under construction and our builders would need ready access to the material and the process, or a contractor that provides both.
I was interested in SafeTouch, but it’s plastic-based and I can’t find anything about its fire-resistance (or lack thereof).
Incidentally, we are planning to use a spray-in foam for the exterior walls for its superior R-value. 'Not really sure how that holds up to fire, but even if it holds up well, we don’t want to use it for our interior wall sound-deadening because it’ll create a logistical nightmare for our builders (and therefore a financial nightmare for us).
So in a nutshell, we’re looking for a safe, fire-retardant, mold and vermin resistant, readily available insulation with good sound deadening capability. By safe, I mean no formaldehyde or other toxins or fibers that will cause health issues.
Cinder block?
Lowes is expected to be the sole distributor of a polyester-type insulation that should work for you. However, it’s not supposed to be available until June.
If you’re expecting real sound control from insulation alone, you’re going to be disappointed. Sound is transmitted through the framing, wallboard, and other materials used to build a house. Insulating the interior wall cavities will stop only a small amount of the sound transmission between rooms. You’ll spend a lot of money on insulation for all of those cavities and you’ll discover that you can still hear everything that goes on in the house.
To really prevent sound from traveling from one room to another, you need to do a lot more. By the time the sound is inside the wall cavity, it’s too late. You need to prevent it from getting there in the first place, which means sealing any openings in the wall. You also have to mechanically isolate one side of the wall from the other. This can be accomplished with membranes that provide for separation between the drywall and the framing. There are also special construction techniques that can be employed, but they generally result in very thick walls, so they’re not practical for a whole house - they are usually used when constructing a single room that requires isolation, such as a theater or music studio.
Don’t rely on a builder to know anything about this. They will happily install the extra insulation (for a price), but when it doesn’t work you’ll have no recourse. What’s worse is that you’ll have no practical way to fix it - you have to do this before the drywall goes up. After that you might as well sell and build a new house the right way.
Also, remember that as soon as you open a door you lose almost all of the benefit of soundproofing.
I forgot to mention that I had my garage insulated with Icynene expanding foam insulation. The ceiling had a good 10 inches of the stuff. The sales guy and the installer both noticed my woodworking tools and said that nobody would be able to hear a thing in the rest of the house. I knew they were wrong, and they were. It was an improvement over the fiberglass batts that had been there, but not that much of an improvement. Certainly not enough of an improvement for them to make the claims they do for the stuff.
My safe is lined with cinderblock, which makes it pretty much fireproof. Individual storage bins in the safe (it’s a walk-in model) are also fire-resistant.
What?
I don’t understand your bias against fiberglass. Yes it itches, and you should wear a respirator. But once the wall is up, all of this is past.
The wallboard encapsulates the fiberglass and there is no need for concern for the residents.
Stone Wool! It’s melted and spun stone. See Here
How about recycled denim?
Cellulose is safe. Boric acid is safe for mammals and can help prevent roach infestations. It also handles small water intrusions better than fiberglass since the cellulose wicks the water away, allowing it to evaporate before mold can get a start. It makes a mess when blown in though, which is why it is wetted slightly when blown into walls.
I think that Gus Gusterson hit the nail on the head with respect to sound deadening. One accepted method is to build two sets of interior walls (rather than having adjoining rooms share a wall), and not have them touching each other by staggering the studs. Hence his comment about thick walls.
One thing that I have found: I’ve been replacing lath and plaster walls with sheetrock. The lath and plaster of the old walls together measures 3/4" thick, fairly consistently. Rather than reworking all the door and window casings, I’ve been putting on two layers of 3/8" sheet rock, staggering the joints. The bonus to this is that it seems to do a fairly good job of deadening sound.
Interior walls would need to be 2x6 with the studs for adjacent rooms offset. Probably needing spray, blown-in, or pre-formed insulation. Interior doors will have to be filled to reduce resonsnce (they are hollow core). Frames will also re-broadcast interior noises; composite (fake wood) transmits less sound. None of aforementioned will really kill noise though.
You said you want all interior walls. Sounds impractical and expensive. Typically just a home theater addition or new construction would make use of acoustical tile (engineered material not just ceiling stuff that accidentally knocks off a few dB). The tile would need a standoff from the walls. Heavy drapes along the walls as well as a thick carpet/pad combine to deaden the acoustics.
Sounds as if the floor plan is settled. Ideas for next time: Segregate master bedroom at one end of house. Second set of walls and air space to living area would be made up of wall closets, mud/laundry room, and master bath. Same at guest/children bedrooms; split off by closets and bathrooms from the living area.
I don’t understand the mold/vermin concern? These are INTERIOR walls. If you are worried about condsation or leakage; you need a new contractor. Same with vermin; a new contractor and/or cat.
Lastly, don’t worry about the children and noise. They can be seen sullenly slinking around the house with ear buds draped from their heads. Note to parents: Yes, the buds have steep notch sound filters that are listener adjustable to the typical frequencies of parent’s voices.