Some questions about the inside out wall design

[JCBigler]

A couple of questions about the inside out wall design:

1) When, using the inside-out wall design, do all of the walls in your room have to follow that same design? Can you have the side walls be inside out, and the front and back as standard? How do you get the dry wall to join up in order to seal properly when doing that?

B) What are some other wall coverings that can be used on the inside of the walls other than the wooden slat resonators or panels? They look nice in some areas, but having all of the walls covered with the same slats would kind of make me feel like I'm living inside a tree.

And finally) when you have two adjacent rooms both built with the inside out walls, how does the mass-space-mass construction get affected when the insulation is now on the opposite side of the mass (i.e. dry wall that is now facing each other)...And do you have to maintain the same amount of air gap between the walls? ~4 inches? or does that change with the relocation of the mass?

[Soundman2020]

When, using the inside-out wall design, do all of the walls in your room have to follow that same design?

Nope!

Can you have the side walls be inside out, and the front and back as standard?

Yep!

How do you get the dry wall to join up in order to seal properly when doing that?

Don't think of a leaf as being just drywall: the leaf is "mass". any mass will do.... such as a stud, for example.... Even though wood is a bit less dense than drywall, studs are much thicker, and serve just fine to keep the surface density of the wall high enough. At an inch and a half thick, a stud is about the same surface density as two layers of 5/8" drywall. If you really wanted, you could do alternating stud bays as "inside-out" and "conventional" along the entire wall without any problem at all, since the studs that the drywall is nailed to are plenty massive enough for that.

What are some other wall coverings that can be used on the inside of the walls other than the wooden slat resonators or panels?

Fabric, perforated panels, micro-perforated panels, artwork, etc. I have heard of people getting images, words, logos and suchlike printed on breathable fabric, and using that as covering. Lots of ways to skin a cat...

And finally) when you have two adjacent rooms both built with the inside out walls, how does the mass-space-mass construction get affected when the insulation is now on the opposite side of the mass

Ummm... not sure if I understand you there, but there is ALWAYS insulation in the wall cavity, regardless of how you build the wall. If you don't put insulation in the wall cavity, that can cost up to 16 dB of isolation, which is huge. You need to get as much as you possibly can in there, without compressing it.

With an inside out wall you generally also use insulation on the room side of the wall, between the studs, but that has nothing to do with isolation or MSM. That is room treatment. But regardless of what you do in the room side of the wall, the cavity side still needs filling with insulation.}

And do you have to maintain the same amount of air gap between the walls? ~4 inches? or does that change with the relocation of the mass?

MSM isolation is a tuned system: if the distance across the cavity between the two leaves is less in some places, then the mass must be increased to compensate: You can use the MSM equations to figure out how much additional mass you need to make up for the lost cavity depth, to keep the same resonant frequency. Ideally, you don't want less that about 4" of gap in there, or the amount of mass you have to add turns out to be thicker than the space you saved by reducing the air gap... catch 22.


- Stuart -

[JCBigler]

Ummm... not sure if I understand you there, but there is ALWAYS insulation in the wall cavity, regardless of how you build the wall. If you don't put insulation in the wall cavity, that can cost up to 16 dB of isolation, which is huge. You need to get as much as you possibly can in there, without compressing it.

With an inside out wall you generally also use insulation on the room side of the wall, between the studs, but that has nothing to do with isolation or MSM. That is room treatment. But regardless of what you do in the room side of the wall, the cavity side still needs filling with insulation.}

Aha..Ok, I think this is what I did not understand. You still need insulation inside the wall cavity, which is what glued to the drywall just as it would be in between the the studs in a normal wall. That makes more sense now. I will have to adjust my designed accordingly then.

[Soundman2020]

which is what glued to the drywall

Or hung from impaling clips...

impaling-clips-2.jpg

Just screw or nail to the wall (through the drywall, into the stud, of course) up near the top, then impale your insulation on it. Thusly:

impaling-clip-4.jpg

You still need insulation inside the wall cavity

Correct. The purpose of the insulation in the cavity is mostly to act as damping on the various types of resonance going on in there. If not damped, those resonant issues can cost you quite a bit of isolation.


- Stuart -

[JCBigler]

which is what glued to the drywall

Or hung from impaling clips...

impaling-clips-2.jpg

Gaahhh...Those look positively medieval.