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eric himmer Posted: Sep 18, 2009 08:26 PM	Duplex Sound Attenuation Mason, We are spraying closed-cell in the walls of a duplex with the units above one another. The homeowner also wants to spray 1-2" of foam on the bottom of the ceiling and then fill w/ fiberglass to deaden the sound from above. Although open-cell may be a better choice, will the combo of closed-cell and fiberglass be effective (compared to nothing presently)and could this possibly backfire and allow footstep vibration from above to telegraph or louden b/c of the closed-cell rigidity as when you bang your fist on a foamed wall and it shakes/ vibrates ? And should the fiberglass have a vapor barrier or not where both units are heated ? Please advise. Thank You.
mason Posted: Sep 19, 2009 02:28 PM	You are correct, the closed cell foam will allow a virbration noise to be transmitted. I would use the open cell foam and fill up the space. No need for a vapor retarder or fiberglass. The open cell foam will be a good sound absorber and stop air born noise
Posted: Sep 20, 2009 07:56 AM	in a perfect world... 1) 3-4 inch oc type foam before any mechanicals or other schtuff installed in joist cavity...yes they will have to violate the application to install their stuff,,if they are not hotheads they can remove this stuff very easily and professionally,,and it wont bother them a bit,,they need to know about this application at the start..if they wack it out in hunks with reckless abandon,,it will be apparrant that they are azzholes (smile when you tell em just that)and resistant to the changes that will need to be made to remain competitive in this very competitive world,,,but this will assure the best application for the $$ upgrade,,and these breaks can be addressed after the mechanicals are in place...now if it were me i would top this cavity off with a filterglass batt...you know around the mechanicals, over the foam and down to the joist face... i believe there is too much emphisis given to the rigid foams and vibration...except in extreme vibration environments,,,in this app the cc foam at 1-2" would do a nice job "tightening up" the joists and floor assembly,,,no squeaks, creaks,,obviously it would greatly attenuate sound transfered by air movement,,,and then the filterglass over top of the cc foam would also augment the already greatly attenuated sound,,,that being said,,i too prefer oc for sound control...cost and ease of application... becareful selling sound control in multifambly structures,,,you can greatly attenuate the sound of normal daily living,,but the homey with the subwooofer poundin junglerap or ih8everythingkillkill heavy metal thunder..or the 100# chiquita with the 500# footsteps is still gonna be heard,,,and they will biatch at you cause they paid you for "sound controll".. just be sure expectations are realistic...
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Sep 21, 2009 06:13 PM	Warning! Don't fill the space as Mason suggests! If you completely fill the cavity with open cell or closed cell, it will potentially allow more sound to transfer through as it passes through the solid materials. So, you want to leave at least one air space within the cavity. If you can spray a layer of open cell and leave an air spaces on both sides of the batt insulation this is optimal. We use UltaTouch Cotton Batts as these have even better accoustic properties than fiberglass and are recycled blue jean materials. The UltraTouch is being used much much more by sound studios, home theaters, interior walls, and apartments due to it's great sound transmission coefficient. They have tested the R-13 at STC-45 and an R-19 at STC 57. Jim Coler
eric himmer Posted: Sep 21, 2009 08:37 PM	Thanks for the comments. I see there is great difference of opinion. The cost is not a factor, so open or closed cell could be used. We'll already be spraying CC so that would be easiest. The subfloor above is 3/4" T&G pine with some visible gaps and cheap wood flooring over it. You could hear someone whisper if they were at floor level. I agree that the closed-cell might tighten up the airborne noise - maybe 1-2" Whats there now can rattle or vibrate by itself so maybe the CC will glue everything together. Then maybe leave an airspace, then r-13 batts of the cotton batts - my research has led me to look into a high density fiberglass or cotton batt. I'll listen to your experience with the cotton batts. Then thinking resilient channels to hang the drywall from - this will leave another airspace. OR IS THE CLOSED CELL A MISTAKE ? Please comment. Thanks
Dan Beecher Posted: Sep 21, 2009 10:25 PM	You have to look at the whole floor assembly. Big difference if its concrete, wood or carpet above. Best advice is with a sound engineer. I spray open, closed, and spray applied cellulose. A lot of times its a combination of one, two or all three and depending on the surface above and below other "mats" or hat channels. You have to test the whole assembly to get "real results". Like Dude said, be very careful what you promise owners, can really bite you in the you know where. High heels and hardwood floor, you ain't gonna get rid of it.... Kids playin the crap they play, not gonna get rid of it, the only thing that gets rid of bass is MASS and lots of it. Wood to wood not gonna do it. You need to leave air spaces in there, use different materials for optimum STC.
mason Posted: Sep 22, 2009 02:56 PM	All good comments thanks for pitching in. Each situation can be vastly different from another depending on the type of noise you are attempting to muffle. A sound engineer sounds like a good idea to me. A sound engineer can recommend which system to use for which type of noise. (vibration, airborn or structural movement) As some folks suggest, closed cell foam is denser and will transmit vibration noise, (footsteps, dropped objects etc.), but if the actual floor joist is moving and causing the floor to creak then the closed cell foam might provide some structural qualities to reduce movement that causes that type of noise. Open cell has good sound absorbing qualities but not as good as cellulose or other materials specifically designed for sound proofing. As stated earlier both the open and closed cell foams will best stop air born noises by providing an air barrier (most sounds are transmitting through the air and not through materials.)

Author

Comments

eric himmer

Posted: Sep 18, 2009 08:26 PM

Duplex Sound Attenuation

Mason,
We are spraying closed-cell in the walls of a duplex with the units above one another. The homeowner also wants to spray 1-2" of foam on the bottom of the ceiling and then fill w/ fiberglass to deaden the sound from above. Although open-cell may be a better choice, will the combo of closed-cell and fiberglass be effective (compared to nothing presently)and could this possibly backfire and allow footstep vibration from above to telegraph or louden b/c of the closed-cell rigidity as when you bang your fist on a foamed wall and it shakes/ vibrates ? And should the fiberglass have a vapor barrier or not where both units are heated ?
Please advise. Thank You.

mason

Posted: Sep 19, 2009 02:28 PM

You are correct, the closed cell foam will allow a virbration noise to be transmitted. I would use the open cell foam and fill up the space. No need for a vapor retarder or fiberglass. The open cell foam will be a good sound absorber and stop air born noise

Posted: Sep 20, 2009 07:56 AM

in a perfect world...
1) 3-4 inch oc type foam before any mechanicals or other schtuff installed in joist cavity...yes they will have to violate the application to install their stuff,,if they are not hotheads they can remove this stuff very easily and professionally,,and it wont bother them a bit,,they need to know about this application at the start..if they wack it out in hunks with reckless abandon,,it will be apparrant that they are azzholes (smile when you tell em just that)and resistant to the changes that will need to be made to remain competitive in this very competitive world,,,but this will assure the best application for the $$ upgrade,,and these breaks can be addressed after the mechanicals are in place...now if it were me i would top this cavity off with a filterglass batt...you know around the mechanicals, over the foam and down to the joist face...

i believe there is too much emphisis given to the rigid foams and vibration...except in extreme vibration environments,,,in this app the cc foam at 1-2" would do a nice job "tightening up" the joists and floor assembly,,,no squeaks, creaks,,obviously it would greatly attenuate sound transfered by air movement,,,and then the filterglass over top of the cc foam would also augment the already greatly attenuated sound,,,that being said,,i too prefer oc for sound control...cost and ease of application...

becareful selling sound control in multifambly structures,,,you can greatly attenuate the sound of normal daily living,,but the homey with the subwooofer poundin junglerap or ih8everythingkillkill heavy metal thunder..or the 100# chiquita with the 500# footsteps is still gonna be heard,,,and they will biatch at you cause they paid you for "sound controll"..
just be sure expectations are realistic...

jimcoler

I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs.

I've expanded my knowledge into t

Posted: Sep 21, 2009 06:13 PM

Warning! Don't fill the space as Mason suggests! If you completely fill the cavity with open cell or closed cell, it will potentially allow more sound to transfer through as it passes through the solid materials. So, you want to leave at least one air space within the cavity. If you can spray a layer of open cell and leave an air spaces on both sides of the batt insulation this is optimal. We use UltaTouch Cotton Batts as these have even better accoustic properties than fiberglass and are recycled blue jean materials. The UltraTouch is being used much much more by sound studios, home theaters, interior walls, and apartments due to it's great sound transmission coefficient. They have tested the R-13 at STC-45 and an R-19 at STC 57.
Jim Coler

eric himmer

Posted: Sep 21, 2009 08:37 PM

Thanks for the comments. I see there is great difference of opinion. The cost is not a factor, so open or closed cell could be used. We'll already be spraying CC so that would be easiest. The subfloor above is 3/4" T&G pine with some visible gaps and cheap wood flooring over it. You could hear someone whisper if they were at floor level. I agree that the closed-cell might tighten up the airborne noise - maybe 1-2" Whats there now can rattle or vibrate by itself so maybe the CC will glue everything together. Then maybe leave an airspace, then r-13 batts of the cotton batts - my research has led me to look into a high density fiberglass or cotton batt. I'll listen to your experience with the cotton batts. Then thinking resilient channels to hang the drywall from - this will leave another airspace. OR IS THE CLOSED CELL A MISTAKE ? Please comment. Thanks

Dan Beecher

Posted: Sep 21, 2009 10:25 PM

You have to look at the whole floor assembly. Big difference if its concrete, wood or carpet above. Best advice is with a sound engineer. I spray open, closed, and spray applied cellulose. A lot of times its a combination of one, two or all three and depending on the surface above and below other "mats" or hat channels. You have to test the whole assembly to get "real results". Like Dude said, be very careful what you promise owners, can really bite you in the you know where. High heels and hardwood floor, you ain't gonna get rid of it.... Kids playin the crap they play, not gonna get rid of it, the only thing that gets rid of bass is MASS and lots of it. Wood to wood not gonna do it. You need to leave air spaces in there, use different materials for optimum STC.

mason

Posted: Sep 22, 2009 02:56 PM

All good comments thanks for pitching in.

Each situation can be vastly different from another depending on the type of noise you are attempting to muffle.

A sound engineer sounds like a good idea to me.
A sound engineer can recommend which system to use for which type of noise. (vibration, airborn or structural movement)

As some folks suggest, closed cell foam is denser and will transmit vibration noise, (footsteps, dropped objects etc.), but if the actual floor joist is moving and causing the floor to creak then the closed cell foam might provide some structural qualities to reduce movement that causes that type of noise.

Open cell has good sound absorbing qualities but not as good as cellulose or other materials specifically designed for sound proofing.

As stated earlier both the open and closed cell foams will best stop air born noises by providing an air barrier (most sounds are transmitting through the air and not through materials.)

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