This is out there, I can't vouch for the information
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
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
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I believe the difference in your example and the situation of the original post is this:
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.
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.
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.
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.
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.