[strider]

We're in the process of remodeling the basement in our duplex. It serves multiple purposes, family room w/television, craft room, as well as home to my 2 channel system. My personal goal WRT the remodel is trying my best to insulate the upstairs rooms from the sound of evening listening sessions without adding significantly to the bottom line cost. The basement ceiling is unfinished currently, with furring strips attached to the bottoms of the floor joists in a perpendicular orientation. The flooring above is 1" oak. My plan is to drywall the ceiling with one thickness of 1/2" drywall, glued and screwed to the furring strips. I also plan to fill the cavities between the joists with insulation to assist in blocking sound transmission through the floor. Is Roxul (or similar stone wool product) worth the price (pretty much double) vs insulating with fiberglass such as Owens Corning? Couldn't find any specs online for sound transmission. Thanks in advance.

[pslate]

I get involved in spec writing at my firm, here's my two cents. Mineral wool will have better IIC ratings as a part of an assembly. It is also be more dimensionally stable and does not degrade with moisture. Worth the dough, tough to say, but if I wanted to put in a drywall ceiling and forget about it. mineral wool would be the way to go. Fiberglass would work great too, maybe a good choice if this is not your forever home. In either case workmanship can be the difference maker, small gaps can sometimes kill IIc or STC ratings.

[bpape]

IMO, the money for the denser rockwool would be better spent increasing the mass of your ceiling, the underside of the subfloor above, or both.  The insulation in that case is purely to damp the cavity and keep it from ringing as we've already then lowered the resonant frequency of the cavity.

Bryan

[Atlplasma]

I've been investigating sound isolation strategies for a new house and came across this link:

http://www.soundisolationcompany.com/index.php/soundproof-walls/quietclip

This company makes an interesting argument for decoupling rooms to improve sound isolation.

For insulation, you might want to check out Engard as well. Like rockwool, it is not affected by moisture like fiberglass, which is a nasty material to put into your structure in any case.

[strider]

pslate: Definitely not going to be our last home, we're hoping to be here less then 5 more years. I don't want to build a time bomb for the next owner, of course, but...Does IIC just deal with sound due to impact? I've seen STC, but not IIC. I hear you regarding workmanship possibly killing the effort, wish my wife did as well.

Bryan: what are some methods of adding mass to the subfloor above? It is constructed of 2x10 lumber run at 45 degrees WRT the joists. Oak floor attached to it, toenailed through the tongues of the tongue and groove sides. I'd thought about adding a second layer of drywall (or homasote), but have concerns about that much weight hanging from the furring strips.

To give a sense of scale to the budget, my query is dealing with an increase from $150 for fiberglass insulation to about $300 for rockwool.

[Big Red Machine]

Not that you want to spend a bunch of money on this duplex, but it will be a waste of money for any kind of insulation if you don't isolate the two spaces from one another.  If you can double drywall with green glue in between and hang that on rubber isolators then you will have much better happiness all around.  Heavy mass that vibrates less than one sheet of drywall and is isolated from the other room's "mass" is the solution.  Otherwise just use regular insulation in the ceiling and get what you get, which will be foot-traffic from above and audio going up.  Noise is like water, it will find a way to "seep" from one space to another.

I used the Isomax version:  http://www.soundisolationcompany.com/index.php/soundproof-walls/isomax-clips

[Big Red Machine]

It's essentially too late to add mass to the first floor.  Too bad you couldn't bring those furring strips down and insert the isolator clips between them and the joists.  Then double drywall it, overlap the joints on the second drywall application using at least 50% green glue coverage.

You can find a bunch of discussion on building "sound proof" rooms over on AVS in their HT build threads and see what some folks are doing mid-build.

pslate: Definitely not going to be our last home, we're hoping to be here less then 5 more years. I don't want to build a time bomb for the next owner, of course, but...Does IIC just deal with sound due to impact? I've seen STC, but not IIC. I hear you regarding workmanship possibly killing the effort, wish my wife did as well.

Bryan: what are some methods of adding mass to the subfloor above? It is constructed of 2x10 lumber run at 45 degrees WRT the joists. Oak floor attached to it, toenailed through the tongues of the tongue and groove sides. I'd thought about adding a second layer of drywall (or homasote), but have concerns about that much weight hanging from the furring strips.

To give a sense of scale to the budget, my query is dealing with an increase from $150 for fiberglass insulation to about $300 for rockwool.

[pslate]

STC is the better measure, but often times it's hard to find values for floors. STC is more common for walls while IIC is more common for floor assemblies. Impact isolation does correlate acoustical performance, maybe just not as exactly as STC. It really is amazing how very small gaps can kill you, either way that is something to concentrate on. Also I'd rather work with mineral wool than fiberglass, but maybe I'm being a wuss 

[strider]

We're too far in at this point to alter the construction of the sub-ceiling (guess that's what you'd call the furring strips, etc.) without significantly adding to the cost and time table, neither of which are going to go over well with the "project manager".

Again keeping the budget in mind, if I were to double the drywall only above the listening area, would that have any impact on the sound heard above? Or would the sound just find another path to get upstairs? The listening area is the front half of the basement, which has a completely open floorplan. The master bedroom is two stories directly above it, which is where the annoyed typically resides at night when I'm listening.

The ceiling/floor construction I have with one layer of drywall attached to the joists would have an STC rating of 38 according to one site I found. It claims insulation would add another 5 to that rating. Any truth to that in your experiences?

[cheap-Jack]

in the process of remodeling the basement in our duplex.
The basement ceiling is unfinished currently, with furring strips attached to the bottoms of the floor joists in a perpendicular orientation. The flooring above is 1" oak.
My plan is to drywall the ceiling with one thickness of 1/2" drywall, glued and screwed to the furring strips. I also plan to fill the cavities between the joists with insulation to assist in blocking sound transmission through the floor

You are now dealing with 2 different things:-
(1) noise transmission between the main floor & the basement.
(2) acoustics for yr audio in the basement.

(1) Yes, it is a good idea to cover up the basement unfinished ceiling by installing drywall panels with in-fill noise absorbing materials, e.g. rockwool or whatever.

(2) That said. Drywall with standard plaster & the like finish is no good acoustically for yr stereo & home theatre.

Way to reflective! I've auditioned a few audioiphiles' home with similar drywall ceilings & was not impressed at all acoustically. One common problem:- ringing at HFs when cranking up the volume.

FYI, I had a very similar situation of yours 20 years back when I moved in my house. Hardwood flooring on wooden main floor & basement (where I installed my audio) ceiling (9-ft clearance from the basement concrete floor) was unfinished.

To sorta kill 2 birds with one stone, I installed a 2-ft standard drop ceiling with 2'x4' glassswool ceiling tiles, leaving only 7 ft clearing for my audio!
The surrounding bare concrete walls were all covered with thin wooden panels with standard wooden studssupport at the back plus  glasswool in-fills.
The concrete floor is covered with wall-to-wall carpet with thick rubber underlay.

NO no special costly acoustical treatment at all. Honestly, I don't buy such thing. My music sounds superb with no HF ringing nor boomy bass even cranking up very loud to 90dB! It delivers pipe organs 30Hz sub-sonic bass notes (via my 10" active sub) no sweat - clean & substantial!

My tube power amp is only 15Wx2. No big power guns!

c-J

[bpape]

If the basement is open, that's going to be a huge source of noise transfer and likely, standard insulation, slats, and regular drywall is your best reasonable option.  I wouldn't bother with a ton more if the rest is open and the sound is just going to to right up the stairs.  A solid core wood door on the stairwell would be a better investment IMO.

Bryan

[cheap-Jack]

Hi.

A solid core wood door on the stairwell would be a better investment IMO.

Yes, the wooden door down the basement stairway is always kept CLOSE
during my music sessions. This surely cut down noise up/down.

c-J

[strider]

If the basement is open, that's going to be a huge source of noise transfer and likely, standard insulation, slats, and regular drywall is your best reasonable option.  I wouldn't bother with a ton more if the rest is open and the sound is just going to to right up the stairs.  A solid core wood door on the stairwell would be a better investment IMO.

Bryan

Thank you for the response. Looking at costs/materials again last night after I logged off here, I think that's the course of action we are going to go with. Whatever I add will be an improvement to what's there now.

[christopher22dude]

Just came across this article, I realize it's old but I will add some input.  I'm surprised no one has posted the absorption coefficients of all the materials here in AudioCircle. 
Here's some numbers for absorption coefficients for your own calculations http://www.bobgolds.com/AbsorptionCoefficients.htm

Basically though people just want to know if Roxul safe'n'sound is worth it or not.  I don't know if it's worth it but it is heavier and will provide a better sound barrier than the pink fiberglass.  Also Fiberglass is full of glass fibers and you should wear a mask, Roxul is safer in that respect.  As well, fiberglass is lighter and will puff out Roxul will stay crushed.  Both are good but you want the heavier Roxul for sound insulation and the lighter puffy fiberglass for heat insulation. 

Generally people use sound insulation when adding a new room in the basement.  As people have mentioned mass is your friend to reducing sound transfer as well as complete isolation from joists.  Those heavy feet upstairs are not going to be dampened much if your drywall ceiling is screwed directly into the joists, even if you have two sheets on the ceiling.  For the ceiling you want to be isolated with rubber dampers or some sort of separation to attenuate the sound.

Back to the cost, if you're going to use pink fiberglass in the ceiling forget it, you'll never notice the difference.  And if you did measure the sound levels it would only slightly differ.  Some people even buy R24 or R23 instead of R13 or R16 batts and in effect stuffing batts meant for 24" center into the 16" centers more fiberglass more damping ... yes that works to some extent - you're adding more mass but only slightly.  Again Roxul is heavier and will provide even more damping than the fiberglass. 

You'll be happier with the Roxul if you decide to use it.  I'm doing the same in my own basement and I was contemplating stuffing more insulation fiberglass instead of using the Roxul but I believe I'm going to use the Roxul safe'n'sound. 

This being an old post, I hope your insulation worked out

[ctviggen]

We're too far in at this point to alter the construction of the sub-ceiling (guess that's what you'd call the furring strips, etc.) without significantly adding to the cost and time table, neither of which are going to go over well with the "project manager".

Again keeping the budget in mind, if I were to double the drywall only above the listening area, would that have any impact on the sound heard above? Or would the sound just find another path to get upstairs? The listening area is the front half of the basement, which has a completely open floorplan. The master bedroom is two stories directly above it, which is where the annoyed typically resides at night when I'm listening.

The ceiling/floor construction I have with one layer of drywall attached to the joists would have an STC rating of 38 according to one site I found. It claims insulation would add another 5 to that rating. Any truth to that in your experiences?

I put insulation in my ceiling, and it did help a little. However, if I had it to do over again, I'd have put in hat channel and isolation.  Every time the kids put something on the tile floor in the kitchen, the sound easily traveled to the basement.  The only way to reduce that sound is via decoupling. 

Something like this is what I mean:

http://www.soundproofingcompany.com/soundproofing101/furring-channel-with-resilient-sound-clips/

I also got two heavy, solid doors.  I ordered them from a local company and had them install rubber around the doors.  Add an automatic door bottom, and that will help too:

http://www.soundproofingcompany.com/soundproofing-products/door-bottom-jamb-stop/automatic-door-bottom/

[gregfisk]

I put insulation in my ceiling, and it did help a little. However, if I had it to do over again, I'd have put in hat channel and isolation.  Every time the kids put something on the tile floor in the kitchen, the sound easily traveled to the basement.  The only way to reduce that sound is via decoupling. 

Something like this is what I mean:

http://www.soundproofingcompany.com/soundproofing101/furring-channel-with-resilient-sound-clips/

I also got two heavy, solid doors.  I ordered them from a local company and had them install rubber around the doors.  Add an automatic door bottom, and that will help too:

http://www.soundproofingcompany.com/soundproofing-products/door-bottom-jamb-stop/automatic-door-bottom/

From what I have read and discussed with various people Hat Channel is the best way to go. This is what is used in condos and apartments between living spaces. It's just a matter of having the drywall company install the strips before they put up the sheet rock. This decouples the sheet rock from the ceiling and makes the most difference for the money I'm told. I'm currently building an out building 20'x30'x10' as an audio room/guest house and will be using it on all outside walls including the ceiling. My concern is keeping the sound in more than keeping it out but I understand it works both ways equally well. Rock wool is also supposed to be better than fiberglass but is it worth the cost I don't know.