Sound proofing with Insulation
rdg732000
| Posted in Energy, Heating & Insulation on
I am remodeling the first floor of my 2 family home and have a tenant living upstairs. I want to sound proof the ceiling of the first floor apartment . I’ve been told that open-cell spray foam insulation is very good for soundproofing. Would using open-cell spray foam be a significant improvement over batt insulation? Also, what thickness of each kind of insulation would be best if the space to be filled is 8 inches deep?
Replies
I cannot give you all the answers
but I'll try for one with this suggestion. Mass is important. You can acheive that with what you attach below any insulation you use. De coupling the joists from what the finish is attached to is also important. Using resilient channel and two layers of drywall, or channel and one layer of homasote topped by drywall will do much to improve your noise reduction.
How to Soundproof a Wall Separating a Bedroom From a Family Room This video has some good info on soundproofing:
I agree w/ others ... insulation alone isn't all you should consider.
A "standard" code option for your case would be hat channels running perp to joists and two layers of drywall. When I did my house w/ a basement apartment, that is what I HAD to do. This technique combines the mass w/ the isolation that someone mentioned. Isolation using the hat channels perp to joists. Mass using extra drywall.
You might talk w/ the building official. There's a whole list of options for sound separation of e.g. apartments like this. Personally, I wouldn't do the expense of foam insulation ... although I'm not a sound expert. If you are going to spend the money, I'd use sound batts ... I think they are made w/ rockwool insulation as maybe your best choice ... it's the standard in the commercial industry. Or you could use the foam they install in anechoic chambers.
DanH has some good info there. I would caution everyone regarding the contents of that video. Quite a few classic errors in it:
The wall framing is "coupled" and therefore not as effective in stopping the bass frequencies.
Given that the wall is coupled, the thing to do would be to frame at 24" OC, not 16"
The floor, side walls and ceiling will allow sound to travel around the wall in question. This is callled Flanking: http://www.soundproofingcompany.com/library/articles/flanking/
There are huge vents in the gable that will conduct sound easily. Right past the drywall.
Spray foam is well known and well documented to be about the worst thing to put in any sound isolated wall. http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/ir/ir693/ir693.pdf
The specialty drywall ($80 a sheet) used will yield a relatively low mass solution, and mass is a main part of any isolation slution. Better to have used standard ($8 a sheet) 5/8" drywall.
Lastly, this entire treatment would have performed much better if installed on the sound producing side of the wall, thereby reducing the sound from entering the wall framing in the first place.
"Lastly, this entire
"Lastly, this entire treatment would have performed much better if installed on the sound producing side of the wall, thereby reducing the sound from entering the wall framing in the first place."
That would have been good ... if it had, in fact, been a wall ... the question was about a ceiling.
Rock-Sol and resilient channels
I am in the process of doing exactly the same thing in my duplex. My wife is the Architect and know the specific numbers better than I, but this is the gist of it.
No foam. Use batts. Rock wool is best and adds more fire resistence than most other insulating products. Unfaced fiberglass is the next best choice.
Resilient channels and 5/8" GWB, as Dan correctly pointed out, a very important part of this assembly. All items make a difference, but individually not that much. It is a system, and when installed as such, works best.
Good luck.
I would reconsider the RC channel...
It's a common fallacy to believe that what makes good thermal insulation makes good sound insulation -- there's really very little connection between the two.
The three critical components of sound "insulation" are mass, damping, and isolation. Mass is simply that -- weight. Damping means something that is "gooey" -- something that bends when you apply pressure but only slowly returns to its original shape when you remove the pressure. Isolation means effectively putting soft springs between the surface facing the noise and the surface on the other side.
Which combination of these features should be used in a given situation depends on the nature of the noise (eg, high frequency or low frequency) and the practical issues of thickness, weight, and expense. In a floor/ceiling situation (where you're trying to keep the bottom floor quiet), the main issue is footsteps, and footsteps have a strong low-frequency component. Low frequencies are easily transmitted through the floor joists, so the main target of your work should be isolating the ceiling from the floor joists. This is best accomplished with resilient channel (springs) and heavy (eg two layers) drywall (mass).
[I'll add that in the above triad, things like fiberglass insulation do the damping. True, fiberglass isn't "gooey", but air, flowing through lots of tiny spaces, is (it has viscosity). The sound waves (waves of air movement) flowing through the fiberglass result in turbulence which dissipates energy. This is why foam isn't such a great sound insulating material -- no air movement.
The other relatively easy way to add damping is with layers of relatively stiff sheet material (metal, plastic, drywall) joined by a viscous adhesive. In aircraft, for example, layers of metal foil joined by an adhesive much like rubber cement are used for vibration and sound control. Such a solution requires some degree of "tuning" to get the right combination of sheet stiffness and adhesive viscosity, so they're not generally usable in non-engineered situations. However, there are simple cases (such as vibrating ductwork) where, eg, a piece of vinyl flooring glued to the duct can be effective.
There probably also are resilient channels made with an included damping material (ie, a sort of rubber). Whether these can add enough damping to have any real effect is questionable, however.]
Certainly a reasonable expectation. My apologies.
I wouldn't and don't spec resilient channel. The fact is there is no single standard for its construction. Some is 20 gauge, some 25, some in between. Some are slotted for flex, some are solid, some have holes. The design of the channel is not standardized and likely not acoustically tested. Not something we can count on acoustically. Also according to the industry that manufactures it, resilient channel is likely (statistically) to have some of it will be installed incorrectly (short circuited).
Again, there isn't a standard for strength, flexibility and consequently performance. Drywall Furring Channel, on the other hand, is specified by the Steel Stud Manufacturers Association, along with all other steel framing components. These channels are much more successfully deployed with resilient clips.
This method of decoupling is effective if the steel can act like a spring. Since there's no manufacturing standard, the net result is that you have no idea if the resilient channel is too stiff (no spring) or too loose (no spring).
As mentioned, the Steel Stud Manufacturer's Asociation has a detailed spec requirement for Drywall Furring Channel, complete with load capacity, thickness, and dimensions. Resilient Channel can be made any way a local place cares to, with no performance or safety guidelines from the SSMA.
Much better to use resilient sound clips and Drywall Furring Channel.
But isn't your DFC+clips just a special case of the RC, from a sound isolation point of view? Essentially a "brand" of a generic category?
Hi Dan. It might initially appear that way, but they are, in fact, quite different.
A clip and channel system woiuld have been extensively acoustically tested.
The system incorporates a standardized steel component, the DFC
The system is not at all likely to be short circuited
The system provides much higher levels of isolation as dempnstrated by independent lab test
The system can easily handle the weight of multiple drywall layers, common for high isolation environments.
So you'd tell a guy that he shouldn't use (or should "reconsider using") siding on his house?
Just talking about soundproofing and the reliability / performance of products used.
the reliability / performance of products used.
And those aren't issues for siding, or plumbing products, or roofing???
Thanks Dan!
Sound Proofing
Your best bet in stopping the sound transfer is by using spray foam. The study that states otherwise was paid for by manufacturers of competing insulation products. It actually says it right on the first page. To me, that seems a little biased and I view it more as a commercial than a "study". The tight air seal of spray foam is what stops airflow, which is why it's used in sound studios, home theaters, and in industrial buildings to separate offices from louder machining areas. Look online for spray foam kits you can use yourself to keep costs down, and I am sure you will find testimonials from real people that have had great success in stopping sound transfer with foam.
With all due respect that it
With all due respect that is incorect. The National Research Council (NRC) is owned and operated by the Canadian government. It is the finest acoustics lab in North America, and possibly the world. The study referenced has been peer-reviewed for many years and is a standard research document cited constantly. The suppliers listed on page one most certainly did not pay to have tests falsified. They simply provided materials.
Open and closed cell foams are too dense for acoustic purposes, and offer insufficient fiberous surface area to diminish the energy of a sound wave. Additionally foams can conduct a vibration and couple both sides of a wall (or a floor / ceiling).
We are not looking to seal the stud cavity with foam, as there is no airflow from one side of the wall to the other. That is not the mechanism involved when we add absorption (insulation) to a cavity.
Ted, there was a question I had about sound and foam:
I assume the foams used in the tests were the hard curing polyurathane closed cell foams. But I wondered about the foams that don't cure hard, but cure flexible - the Window and Door sealing foams. In addition to stopping air, I would think these would work to dampen sound, unlike the regular hard curing insulation foams.
Any tests on flexible foam?
At least a soft foam wouldn't transmit sound as well as a rigid foam. But it doesn't have enough included mass to effectively dampen the sound. Actually dampening sound -- absorbing the sound energy and converting it to heat -- is fairly difficult, and most efforts are directed more at reflecting it.
Foams in general have been looked at for a long time and are not spec'd by acoustical designers unless there's some thermal need to compromise the acoustic performance. Open and closed cell foams all fall into that do-not-use category for sound isolation.