Reverse wall construction, as I understand it, is a double wall technique where you put your interior plasterboard on the OUTSIDE of the stud of the INTERIOR wall. Starting from the inside of your studio, you'd have STUD, plasterboard, space, stud, plasterboard. Normal double wall construction would be PLASTERBOARD, stud, space, stud, plasterboard. The idea, though, is that for a given double wall footprint, the reverse wall has more room inside, specifically twice whatever your stud thickness is: 2X3.5"=7" or 185? mm assuming a 3.5" stud, A.K.A 2X4. Your wall treatment can fit between the studs.
The problem is that the plasterboard sheet separation is 3.5" less for a reverse wall, and the only way a reverse wall's STC can equal a normal double wall is if that 3.5" spacing between sheets has little effect on STC. Actually, spacing may make a huge difference in the range of 0-X cm but be negligible for any distance greater than Y cm. So whether that 3.5" is significant kinda depends on what your wall spacing is in the first place. Can anyone point to an explanation or graph of this relationship?
This graphic I've posted here from John Sayers raises a lot of questions about reverse wall construction. If inside the studio is seen as the left side, the fourth pic, titled "Remove One Plasterboard," is the same as reverse wall, only with plasterboard added to the inside. Remove that leftmost sheet and it IS reverse wall. When this sheet is removed, the STC would have to go down considerably lower than 50(this is open to debate I guess but I can't see it any other way), which is pretty lame after going through the trouble of building two walls.
But the picture is incomplete- no distances between sheets of plasterboard are given. At some point of separation, the imagined configuration of the fourth pic with the left-most sheet removed, reverse wall, has to equal that of the fifth pic. Specifically, this would happen when the spacing between the two sheets are equal to the spacing in the fifth pic, assuming you add equal amounts of insulation to the cavity now that the space is equal.
So, assuming 1"(?) separation between walls, the spacing between the sheets in the fifth pic is 3.5" + 1" + 3.5"= 8"(203 mm), and the reverse wall separation is 1" + 3.5"=4.5"(114mm). Another way to look at it, and probably more revealing, is to think of the latter number as just 3.5" less than the former, which makes sense since they are the same configuration just 3.5" more separation. If this 3.5" makes such a big difference, then specifying the spacing between walls is crucial. Any explanation or desription is somewhat meaningless without it.
The 1" wall separation assumption I just made could be a big one. I don't know. Guess it depends on how linear the STC vs separation curve is. Once again showing the incompleteness of this picture and ones like it. Very frustrating.
I have yet to see a picture, graph, or explanation that details the separation between walls, and yet it's obviously crucial.
According to these pics though, at whatever wall spacing they were measured at, reverse wall construction won't get you anywhere near the STC of a regular double wall unless you space the sheets equally. But then that defeats the whole purpose of the reverse wall- which is to save space!
Assuming that the spacing has less and less effect on STC as spacing increases,- which I'm just guessing- the only way a reverse wall can approach the STC of a normal double wall for a given footprint, is if the spacing is big enough to be on the flat part of an STC vs. sheet-separation graph.
So the big question is how fast does that graph flatten out? Anyone? I guess if you trust this graphic and I guess that their spacing was somewhere between 1/2" and 6", it must not flatten out too rapidly since that 3.5" made a pretty big difference.
The problem is that the plasterboard sheet separation is 3.5" less for a reverse wall, and the only way a reverse wall's STC can equal a normal double wall is if that 3.5" spacing between sheets has little effect on STC. Actually, spacing may make a huge difference in the range of 0-X cm but be negligible for any distance greater than Y cm. So whether that 3.5" is significant kinda depends on what your wall spacing is in the first place. Can anyone point to an explanation or graph of this relationship?
This graphic I've posted here from John Sayers raises a lot of questions about reverse wall construction. If inside the studio is seen as the left side, the fourth pic, titled "Remove One Plasterboard," is the same as reverse wall, only with plasterboard added to the inside. Remove that leftmost sheet and it IS reverse wall. When this sheet is removed, the STC would have to go down considerably lower than 50(this is open to debate I guess but I can't see it any other way), which is pretty lame after going through the trouble of building two walls.
But the picture is incomplete- no distances between sheets of plasterboard are given. At some point of separation, the imagined configuration of the fourth pic with the left-most sheet removed, reverse wall, has to equal that of the fifth pic. Specifically, this would happen when the spacing between the two sheets are equal to the spacing in the fifth pic, assuming you add equal amounts of insulation to the cavity now that the space is equal.
So, assuming 1"(?) separation between walls, the spacing between the sheets in the fifth pic is 3.5" + 1" + 3.5"= 8"(203 mm), and the reverse wall separation is 1" + 3.5"=4.5"(114mm). Another way to look at it, and probably more revealing, is to think of the latter number as just 3.5" less than the former, which makes sense since they are the same configuration just 3.5" more separation. If this 3.5" makes such a big difference, then specifying the spacing between walls is crucial. Any explanation or desription is somewhat meaningless without it.
The 1" wall separation assumption I just made could be a big one. I don't know. Guess it depends on how linear the STC vs separation curve is. Once again showing the incompleteness of this picture and ones like it. Very frustrating.
I have yet to see a picture, graph, or explanation that details the separation between walls, and yet it's obviously crucial.
According to these pics though, at whatever wall spacing they were measured at, reverse wall construction won't get you anywhere near the STC of a regular double wall unless you space the sheets equally. But then that defeats the whole purpose of the reverse wall- which is to save space!
Assuming that the spacing has less and less effect on STC as spacing increases,- which I'm just guessing- the only way a reverse wall can approach the STC of a normal double wall for a given footprint, is if the spacing is big enough to be on the flat part of an STC vs. sheet-separation graph.
So the big question is how fast does that graph flatten out? Anyone? I guess if you trust this graphic and I guess that their spacing was somewhere between 1/2" and 6", it must not flatten out too rapidly since that 3.5" made a pretty big difference.
