This is out there, I can't vouch for the information
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MLV hung limp Vs. no MLV
I know that I am probably resurrecting ancient and redundant debates and flame wars; but I am doing it in context of my specific problem which introduces restrictions that may change the typical opinions.
Problem:
4" thick gypsum block parti-wall (not to be confused with gypsum board, aka drywall) between apartments. 8-foot ceiling. Type of sounds to block/reduce - mostly human clamoring and mumbling; often can make out words and sentences; high frequency female voices and very deep male voices, I'm talking as low as Morgan Freeman divided by two.
Limitations:
1) No studs (obviously, it's a block wall), existing wall is a constant, i.e.: cannot be moved nor replaced (it's a shared wall separating co-op units); i.e.: any treatment must be either along or on the surface of the existing wall.
2) The existing wall runs along very narrow hallway on my end; the most that can be contributed is 2.25 inches; any more and the hallway becomes increasingly unusable (short of moving\demolishing the opposite wall to widen the hallway, which is a whole other scope and cost of work - not being considered at this juncture).
Considered solution:
1) Clips (RSIC-1 or Whisper, still deciding which, see P.S. bellow) directly on the surface of the block wall, spaced at 48" horizontally and 24" OC vertically according to the RSIC-1 INSTALLATION GUIDE for CMU walls. Recommended 25ga hat channel. This contributes ~1.5 inches of space between existing wall and the drywall + any other material that will go on the hat channels, for which I have all of three quarters of an inch left.
2) Planning to stuff created space between the hat channels with 1.5" rockwool.
3) Drywall I am considering are 1/2" Quietrock 510 or 1/2" Silent FX, leaning towards the latter; leaving me with 1/4" at this point.
4) !!! MLV - I understand and accept all the arguments that are in favor of simply using more drywall instead of MLV, i.e.: cheaper, easier, etc., they all make sense if you have the space; but with my severe space limitations I am forced to consider MLV, as 1/8" of MLV gives me double the mass of the same thickness in drywall.
Now on to the meat of the question: my plan was to use two layers of MLV - one layer hung limp against the surface of the existing wall (then clips+hat channel, etc.), and second layer attached to the hat channels before the drywall goes on; creating two layers of limply hung MLV inside the assembly (the Rockwool insulation in this case would then live between the MLV layers). However - by doing this am I creating the triple-leaf effect; or in my case the quadruple-leaf? That is - if MLV performs as solid mass (does it?) and limply hung MLV creates an air pocket between itself and the other surface, then I could end up with the infamous and undesirable triple+ leaf effect, couldn't I?
If yes - then doesn't it also mean that applying MLV to a normal stud wall, according to all the instructions out there where MLV is nailed to studs and clips + hat channel then go on top of MLV, also creates a triple-leaf effect, i.e.: drywall+space+MLV+space(insulation)+the other side of the stud wall?
Once I began considering the triple+ leaf effect, I now feel less confident about my plans for including MLV. I am now considering adding a layer of 1/4" drywall instead; however by itself it has only half as much mass as 2 layers of 1 psf MLV and will likely contribute that much less to attenuation; unless maybe I add 1/4" drywall with Green Glue. Will one layer of 1/4" drywall with GG outperform two layers of limply hung MLV? Or at least will perform the same in term of STC but will rule out the possibility of triple+ leaf effect?
Any advice in context of my specific situation is appreciated.
P.S.: about the clips choice - I understand that if one is using enough mass the difference in performance of clips becomes negligible; however in my case where every extra db could make a difference - which clip is considered more effective RSIC-1 or Whisper?
Problem:
4" thick gypsum block parti-wall (not to be confused with gypsum board, aka drywall) between apartments. 8-foot ceiling. Type of sounds to block/reduce - mostly human clamoring and mumbling; often can make out words and sentences; high frequency female voices and very deep male voices, I'm talking as low as Morgan Freeman divided by two.
Limitations:
1) No studs (obviously, it's a block wall), existing wall is a constant, i.e.: cannot be moved nor replaced (it's a shared wall separating co-op units); i.e.: any treatment must be either along or on the surface of the existing wall.
2) The existing wall runs along very narrow hallway on my end; the most that can be contributed is 2.25 inches; any more and the hallway becomes increasingly unusable (short of moving\demolishing the opposite wall to widen the hallway, which is a whole other scope and cost of work - not being considered at this juncture).
Considered solution:
1) Clips (RSIC-1 or Whisper, still deciding which, see P.S. bellow) directly on the surface of the block wall, spaced at 48" horizontally and 24" OC vertically according to the RSIC-1 INSTALLATION GUIDE for CMU walls. Recommended 25ga hat channel. This contributes ~1.5 inches of space between existing wall and the drywall + any other material that will go on the hat channels, for which I have all of three quarters of an inch left.
2) Planning to stuff created space between the hat channels with 1.5" rockwool.
3) Drywall I am considering are 1/2" Quietrock 510 or 1/2" Silent FX, leaning towards the latter; leaving me with 1/4" at this point.
4) !!! MLV - I understand and accept all the arguments that are in favor of simply using more drywall instead of MLV, i.e.: cheaper, easier, etc., they all make sense if you have the space; but with my severe space limitations I am forced to consider MLV, as 1/8" of MLV gives me double the mass of the same thickness in drywall.
Now on to the meat of the question: my plan was to use two layers of MLV - one layer hung limp against the surface of the existing wall (then clips+hat channel, etc.), and second layer attached to the hat channels before the drywall goes on; creating two layers of limply hung MLV inside the assembly (the Rockwool insulation in this case would then live between the MLV layers). However - by doing this am I creating the triple-leaf effect; or in my case the quadruple-leaf? That is - if MLV performs as solid mass (does it?) and limply hung MLV creates an air pocket between itself and the other surface, then I could end up with the infamous and undesirable triple+ leaf effect, couldn't I?
If yes - then doesn't it also mean that applying MLV to a normal stud wall, according to all the instructions out there where MLV is nailed to studs and clips + hat channel then go on top of MLV, also creates a triple-leaf effect, i.e.: drywall+space+MLV+space(insulation)+the other side of the stud wall?
Once I began considering the triple+ leaf effect, I now feel less confident about my plans for including MLV. I am now considering adding a layer of 1/4" drywall instead; however by itself it has only half as much mass as 2 layers of 1 psf MLV and will likely contribute that much less to attenuation; unless maybe I add 1/4" drywall with Green Glue. Will one layer of 1/4" drywall with GG outperform two layers of limply hung MLV? Or at least will perform the same in term of STC but will rule out the possibility of triple+ leaf effect?
Any advice in context of my specific situation is appreciated.
P.S.: about the clips choice - I understand that if one is using enough mass the difference in performance of clips becomes negligible; however in my case where every extra db could make a difference - which clip is considered more effective RSIC-1 or Whisper?
1 - 15 of 15 Posts
Thanks. I've seen those. I am looking more for experienced opinions which take into account the limitations of my specific situation. Also, these don't address my concerns about MLV and triple-leaf effect.
Here’s an article that might help explain the consequences of different assemblies. Also, you will need to figure out how to attach the mlv to whatever piece of the assembly you might decide on.
Understanding the triple leaf effect and air cavity depth
Understanding the triple leaf effect and air cavity depth
I've read that one. I think I understand the triple-leaf effect. I am just wondering if MLV is a "leaf" or not. i.e.: when hung limply, does it act as mass in much the same way drywall does?Here’s an article that might help explain the consequences of different assemblies. Also, you will need to figure out how to attach the mlv to whatever piece of the assembly you might decide on.
Understanding the triple leaf effect and air cavity depth
Your description of the assembly keeps the main air gap the same whether or not you include the mlv (if I understand it correctly). You would be essentially adding some mass to the two decoupled structures. I think that is a good idea. And it appears to me that the problem typically associated with the triple leaf construction wouldn’t be applicable to your situation due to the air gap not really being dissected by the mlv.I've read that one. I think I understand the triple-leaf effect. I am just wondering if MLV is a "leaf" or not. i.e.: when hung limply, does it act as mass in much the same way drywall does?
this vendor of MLV states that MLV will not create a triple leaf, see the Q&A
Article on The Triple Leaf Effect - Trademark Soundproofing
www.tmsoundproofing.com
this vendor of MLV states that MLV will not create a triple leaf, see the Q&A
Article on The Triple Leaf Effect - Trademark Soundproofing
www.tmsoundproofing.com
Thanks for finding that answer Jeff. I suspected that would be the case, but couldn’t say for sure. It is apparently because the mlv doesn’t resonate very much. As an example, take your knuckles and knock on a piece of drywall like you were knocking on a door, then do the same with a piece of mlv. The two sounds will be quite different. Here is the actual answer from the Q&A:
“Hi Brian, As the MLV is a limp material you should not have much of a triple leaf issue there.”
And in the OP’s case, he isn’t really dividing the air chamber up with the mlv. Instead, he is surrounding the air chamber with the mlv. I think his idea is a sound one (pun intended).
"Now on to the meat of the question: my plan was to use two layers of MLV - one layer hung limp against the surface of the existing wall (then clips+hat channel, etc.), and second layer attached to the hat channels before the drywall goes on; creating two layers of limply hung MLV inside the assembly (the Rockwool insulation in this case would then live between the MLV layers). However - by doing this am I creating the triple-leaf effect "
So back to the original question does putting channel on an existing drywall wall create a triple leaf. Assuming the wall is finished on both sides, of course it does it has nothing to do with the MLV.
I spent several days tearing out just such a construction before starting over the correct way by putting the clips and channel directly on the studs, then double layer of DW with GG. This was a bank foreclosure of a partially finished house. It turned out to be a fixer upper for the unsuspecting couple. The bank had lipstick put on a pig and sold it.
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So back to the original question does putting channel on an existing drywall wall create a triple leaf. Assuming the wall is finished on both sides, of course it does it has nothing to do with the MLV.
I spent several days tearing out just such a construction before starting over the correct way by putting the clips and channel directly on the studs, then double layer of DW with GG. This was a bank foreclosure of a partially finished house. It turned out to be a fixer upper for the unsuspecting couple. The bank had lipstick put on a pig and sold it.
So back to the original question does putting channel on an existing drywall wall create a triple leaf. Assuming the wall is finished on both sides, of course it does it has nothing to do with the MLV.
"Now on to the meat of the question: my plan was to use two layers of MLV - one layer hung limp against the surface of the existing wall (then clips+hat channel, etc.), and second layer attached to the hat channels before the drywall goes on; creating two layers of limply hung MLV inside the assembly (the Rockwool insulation in this case would then live between the MLV layers). However - by doing this am I creating the triple-leaf effect "
I spent several days tearing out just such a construction before starting over the correct way by putting the clips and channel directly on the studs, then double layer of DW with GG
View attachment 3139942
I believe the difference in your example and the situation of the original post is this:
“Problem:
4" thick gypsum block parti-wall (not to be confused with gypsum board, aka drywall) between apartments. 8-foot ceiling. Type of sounds to block/reduce - mostly human clamoring and mumbling; often can make out words and sentences; high frequency female voices and very deep male voices, I'm talking as low as Morgan Freeman divided by two.
Limitations:
1) No studs (obviously, it's a block wall), existing wall is a constant, i.e.: cannot be moved nor replaced (it's a shared wall separating co-op units); i.e.: any treatment must be either along or on the surface of the existing wall.”
I haven’t personally seen this type of block wall. But I don’t think that he has the option of removing any drywall and attaching the clips directly to the studs.
One reason I find this subject interesting is because I personally have mlv that I purchased at a big discount from an individual (before I learned there was a better solution) and wanted to use it in conjunction with the double drywall/green glue/isolation clips construction. I currently have it stapled directly to the interior of the studs of the walls surrounding our theater room. I used 1-1/4” staples with plastic discs per the manufacturer’s recommendations. I have installed the isolation clips and hat channel over the mlv. And I intend to install double drywall and green glue onto the hat channel. Attaching the mlv to the metal hat channel would have been better (especially for low frequencies), but it would have been more difficult for one person to install the heavy and floppy mlv by himself (me), because screws and washers would need to be used (in lieu of the quickly installed staples). Plus, I had already invested in the pneumatic staple gun before researching all of this to find out about the better ways. Anyway, it is encouraging to learn that I haven’t created much of a triple leaf effect with the mlv in that location. Therefore, I don’t believe I need to remove the mlv and relocate it. (But I do concede that it would be better if I did.) I intend to try laying mlv on top of the ceiling drywall panels as I am lifting them up with a lift to attach them to the hat channels and clips that I currently have attached to the bottom trusses. If that works out okay, I will at least have the ceiling built with the mlv in the best position.
Thanks Charles. Indeed that is the difference between my situation and most instances out there where an existing stud wall is a given.
You understand exactly correct - I am attempting to add mass on either side of the air gap using MLV. My concern with triple-leaf was that since I am going to try to hang MLV as limply as possible (as recommended by most) - am I introducing a tiny air gap between MLV and my block wall on one side of the decoupling, and a tiny air gap between MLV and the drywall on the other side of the decoupling; they'd be tiny gaps but as far as microscopic sound vibration is concerned it will be going through air, however briefly. I don't know, this is just something that occured to me as I was thinking through the solution. I think (hope?) you are right, that layers of MLV will act more like additional mass than "leaves".
Any words of wisdom as to RSIC-1 vs Whisper?
You understand exactly correct - I am attempting to add mass on either side of the air gap using MLV. My concern with triple-leaf was that since I am going to try to hang MLV as limply as possible (as recommended by most) - am I introducing a tiny air gap between MLV and my block wall on one side of the decoupling, and a tiny air gap between MLV and the drywall on the other side of the decoupling; they'd be tiny gaps but as far as microscopic sound vibration is concerned it will be going through air, however briefly. I don't know, this is just something that occured to me as I was thinking through the solution. I think (hope?) you are right, that layers of MLV will act more like additional mass than "leaves".
Any words of wisdom as to RSIC-1 vs Whisper?
I believe the difference in your example and the situation of the original post is this:
“Problem:
4" thick gypsum block parti-wall (not to be confused with gypsum board, aka drywall) between apartments. 8-foot ceiling. Type of sounds to block/reduce - mostly human clamoring and mumbling; often can make out words and sentences; high frequency female voices and very deep male voices, I'm talking as low as Morgan Freeman divided by two.
Limitations:
1) No studs (obviously, it's a block wall), existing wall is a constant, i.e.: cannot be moved nor replaced (it's a shared wall separating co-op units); i.e.: any treatment must be either along or on the surface of the existing wall.”
I haven’t personally seen this type of block wall. But I don’t think that he has the option of removing any drywall and attaching the clips directly to the studs.
One reason I find this subject interesting is because I personally have mlv that I purchased at a big discount from an individual (before I learned there was a better solution) and wanted to use it in conjunction with the double drywall/green glue/isolation clips construction. I currently have it stapled directly to the interior of the studs of the walls surrounding our theater room. I used 1-1/4” staples with plastic discs per the manufacturer’s recommendations. I have installed the isolation clips and hat channel over the mlv. And I intend to install double drywall and green glue onto the hat channel. Attaching the mlv to the metal hat channel would have been better (especially for low frequencies), but it would have been more difficult for one person to install the heavy and floppy mlv by himself (me), because screws and washers would need to be used (in lieu of the quickly installed staples). Plus, I had already invested in the pneumatic staple gun before researching all of this to find out about the better ways. Anyway, it is encouraging to learn that I haven’t created much of a triple leaf effect with the mlv in that location. Therefore, I don’t believe I need to remove the mlv and relocate it. (But I do concede that it would be better if I did.) I intend to try laying mlv on top of the ceiling drywall panels as I am lifting them up with a lift to attach them to the hat channels and clips that I currently have attached to the bottom trusses. If that works out okay, I will at least have the ceiling built with the mlv in the best position.
Your description of the assembly keeps the main air gap the same whether or not you include the mlv (if I understand it correctly). You would be essentially adding some mass to the two decoupled structures. I think that is a good idea. And it appears to me that the problem typically associated with the triple leaf construction wouldn’t be applicable to your situation due to the air gap not really being dissected by the mlv.
Personally, I chose the genie clips. But I don’t know that there is enough difference in performance to matter much. They claim that these perform better for low frequencies.
Genie Clips
A suggestion that you might want to consider is using 1/4” thick MLV located between the hat channel and the new drywall in lieu of installing two 1/8” layers of the MLV at the locations you are considering. This increases the mass of the isolated structure, which is a good thing.
Genie Clips
A suggestion that you might want to consider is using 1/4” thick MLV located between the hat channel and the new drywall in lieu of installing two 1/8” layers of the MLV at the locations you are considering. This increases the mass of the isolated structure, which is a good thing.
Yeah the Genie clip design concept looks awfully like RSIC's. Weirdly I've read somewhere that Whisper clips work best at lower frequencies. Totally confused now; LOL.Personally, I chose the genie clips. But I don’t know that there is enough difference in performance to matter much. They claim that these perform better for low frequencies.
Genie Clips
A suggestion that you might want to consider is using 1/4” thick MLV located between the hat channel and the new drywall in lieu of installing two 1/8” layers of the MLV at the locations you are considering. This increases the mass of the isolated structure, which is a good thing.
I've already ordered a couple of rolls of 1/8" MLV. Shall I install them both onto the hat channel? I can probably attach one layer onto the furring, and somehow nail the second layer to the drywall, then put up the drywall together with the MLV. Will try to stagger everything, naturally.
Yes, I believe that I would put both layers of MLV there. Some contact cement (spray-on) might allow you to stick a layer of MLV onto the back side of the drywall. Then when you install the screws through the drywall and into the hat channel they will also hold the MLV in place. Also, overlap the pieces and tape and/or caulk the seams. Acoustiblok has some tape that works well. And I do believe that the Whisper Clips are very similar to the Genie Clips. Either one probably performs about the same.Yeah the Genie clip design concept looks awfully like RSIC's. Weirdly I've read somewhere that Whisper clips work best at lower frequencies. Totally confused now; LOL.
I've already ordered a couple of rolls of 1/8" MLV. Shall I install them both onto the hat channel? I can probably attach one layer onto the furring, and somehow nail the second layer to the drywall, then put up the drywall together with the MLV. Will try to stagger everything, naturally.
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