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Old 7th June 2020
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More STC gain by using better than R13 in Green Glue-treated wall?

Hi,

On this page of the Green Glue company website, there's a wall that achieved a test result of STC 64. (Sorry, can't link directly to the particular item, but it's the 4th row down in their table and it's the only example on the page with STC 64. Attached is a screen-shot image of the wall build.)

Staggered studs or double-stud with air gap is not an option in my space, so this is the model I'm planning for my build, and I'd be pretty happy with STC 64 for the walls. But higher STC would be better, so I'm thinking. . .

The existing steel studs in my space are at least 6" deep, rather than the 3-5/8" in the Green Glue example build. That being the case, it seems that I have room in the wall cavity for insulation thicker than the R13 listed in the GG site's example. So, with all else being equal, would installing insulation thicker than R13 yield STC higher than 64? Common sense says that, yes, of course it would. . . but I'm learning that "common sense" doesn't apply in the realm of physics, heh-heh. (Still trying to wrap my head around the "triple leaf effect.")

Another question. Any ball-park estimates on what (if any) additional STC yields might be achieved by adding a 3rd and even 4th layer of drywall/Green Glue on the side of the wall that has the iso-clip/hat channel? I realize this would require additional clips and channel to handle the load of the add'l drywall layers. (BTW, more than two layers of drywall on the other side of the wall is not an option. Add'l layers would have to be on the clip/hat-channel side.)

Thanks for your help.

Jeb
Attached Thumbnails
More STC gain by using better than R13 in Green Glue-treated wall?-greenglue-wall-stc64.png