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PostPosted: Sun Jan 21, 2018 1:27 am 
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Posts: 6
Location: Glenwood, MD
Hi Everyone,

I've only posted one time in this forum but have been lurking around for a few months gathering information in order to help plan my iso booth build. I have a rectangular control room (13' 6" wide, 20' deep, 8' ceilings) that is adjacent to my (in progress) iso booth. I'm attaching a design so it's a little more clear.

The control room is finished and the existing wall (the wall directly in front of the listening position that has the hole in the drywall I cut out for the glass window) is 1/2" drywall. For the iso booth, I built a room inside a room (two leaf wall system). Most of my design research came out of reading Rod Gervais' book "Home Recording Studio-Build It Like The Pros". I used 2x4's for my framing materials and left one inch of space between each leaf, as advised. I'll be putting up 2 layers of 5/8" drywall on all interior and exterior sections of the iso booth this week (minus the control room side) along with Resilient Channel 1 for walls and RC2 for the ceiling. I'll be using Green Glue in between layers of drywall.

So, I have some questions with a few aspects that I'm having a difficult time with and I was hoping to get some advice from the forum:

1. I'm not sure what the thickness of both pieces of laminated glass should be. In Rod's book, he mentions that 2 layers of 5/8" drywall (for my iso booth side) is 5.25psf of mass but then there is an excerpt where I'm not clear on how to extrapolate that to determine the glass thickness required for both sides. The control room side of my studio only will have one layer of 1/2" drywall (not ideal but the hand that I was dealt since it was already a finished room). He also mentions if using Green Glue to determine the equivalent mass for the window assembly. I really don't have any idea how to do that or where to start as far as figuring that into the calculation. :(

2. In Rod's book, he mentioned in the type of 2 leaf system I have that he uses rigid fiberglass over continuous rubber seal (see attached picture) and then fabric wrapped rigid fiberglass trim. I'm having a difficult time visualizing what this would look like (in real life vs a black and white image). Does anyone have any links to real world images of this type of setup so I can get a feel for what it actually looks like? Also, I was wondering if anyone has any recommendations regarding manufacturers of these products (and who sells them). For example, what should the dimensions of the rubber seal be and who makes/sells this material?

3. I was interested in putting desiccant in my window setup to avoid condensation buildup but I'm not sure where I can "hide it" so it's not visible. Does anyone have any recommendations for this?

If it would be helpfully, this is a link to a 45 second youtube clip that shows the build:

https://www.youtube.com/watch?v=HXmqLPs ... e=youtu.be

I appreciate anyone taking the time to read this and respond. Obviously getting answers will help me complete the build but I'm genuinely curious about this information and would love to be able to pass it on to someone else that needs it in the future.

Thank you for your time!

Bob Goldberg


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PostPosted: Wed Jan 24, 2018 3:06 am 
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Joined: Sat Oct 07, 2017 10:35 am
Posts: 6
Location: Glenwood, MD
Anyone have a chance to read this post? Would really love to get some feedback.

thank you,

Bob Goldberg


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PostPosted: Wed Feb 14, 2018 1:56 am 
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Joined: Sat Oct 07, 2017 10:35 am
Posts: 6
Location: Glenwood, MD
Last call for any advice, guys. I'm having to move forward with ordering the laminated glass for the window in the next few days to finish construction and hoping someone might be able to chime in before I do so.

thanks,
Bob Goldberg


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PostPosted: Wed Feb 14, 2018 3:56 am 
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Joined: Thu Aug 21, 2008 10:17 am
Posts: 11344
Location: Santiago, Chile
Hi Bob, and welcome to the forum! :)

Sorry about the delay, but I'm on vacations right now, at a remote location with only flaky internet connection.

Quote:
has the hole in the drywall I cut out for the glass window) is 1/2" drywall.
1/2" drywall is not very thick, so it seems that you don't need high isolation here? Is that the reason why you used such thin, low-mass sheathing?

Quote:
I used 2x4's for my framing materials and left one inch of space between each leaf, as advised.
Do you mean "one inch from drywall face to drywall face across the cavity, with inside-out walls", or "one inch between the stud frames, with conventional walls, and thus 8" from drywall face to drywall face across the cavity"?
Quote:
I'll be putting up 2 layers of 5/8" drywall on all interior and exterior sections of the iso booth this week
Whoa! That sounds strange! If the booth itself has both an inner and an outer leaf, yet it is built inside another room, that sounds like you have a three-leaf system, or even a four leaf system, with the resulting poor isolation. Please draw and post an accurate, clear diagram of how your leaves and walls are arranged.

Quote:
1. I'm not sure what the thickness of both pieces of laminated glass should be.
The general rule is that each leaf should be consistent in surface density throughout. So for example if the surface area where the drywall is happens to be 12 kg/m2, then the glass must also be at least 12 kg/m2, the doors must be at least 12kg/m2, the HVAC silencer boxes must be at least 12kg/m2, the electrical penetrations must be at least 12kg/m2, the ceiling must be 12kg/m2, etc.. Consistency throughout. Isolation is only as good a the weakest link, so it you have one area of that hypothetical room that is only 8 kg/m2, then the entire rest of the room is wasted expense, because the part that is 8 kg/m2 is what rules.

So, first you need to figure out the surface density of each leaf, then you need to get glass that is thick enough to have at least that same surface density, and preferably a bit more.

Quote:
The control room side of my studio only will have one layer of 1/2" drywall (not ideal but the hand that I was dealt since it was already a finished room).
Somewhat less than "not ideal", I'd say! That's very low mass, thus implying very low isolation.
Quote:
the hand that I was dealt since it was already a finished room
However, you DID have access to the other side of that leaf, apparently, so you could have beefed that up with substantially more mass, between the studs.... I'm assuming this is the case, since you say yo have two-leaf walls, and you built the iso-booth next to the control room: therefore you MUST have had access to the studs on the CR wall before you put up the iso booth wall.... So I'm wondering why you didn't use that opportunity to add more mass to the CR wall? I'm almost certain that Rod mentions this in his book (but I may be wrong...)

Quote:
He also mentions if using Green Glue to determine the equivalent mass for the window assembly.
I don't recall seeing that in his book. Maybe you could quote exactly what he said there? Perhaps you misunderstood? I do recall him saying that if you can't afford the Green Glue then you can get a similar effect from adding yet another layer of 5/8" drywall, but I don't recall him saying that the mass of a layer of drywall is equivalent to the mass of a layer of Green Glue.

Quote:
2. In Rod's book, he mentioned in the type of 2 leaf system I have that he uses rigid fiberglass over continuous
That's one way of doing it, but I use a different method with my customers. Here's a sequence of photos from one of them in Australia, showing how he built the windows that I designed for him:


First, the inner.leaf window frame under construction:
Attachment:
BRAUS-window-01--main-outer-frame.jpg



Now both frames (inner-leaf and outer-leaf) together, temporarily joined together with bracing pieces that will be removed later. Note the black cloth covering the gap between them, all the way around, stapled and taped to hold it in place permanently, stretched taught.
Attachment:
BRAUS-window-02--both-outer-frames-cloth-and-tape.jpg



Both frames together, as a unit, presented into the rough opening and ready to be fixed in place:
Attachment:
BRAUS-window-03--both-outer-frames-in-place.jpg



Interior retainer strips added, and glazing tape placed all around the edges, for the glass to rest on and seal against:
Attachment:
BRAUS-window-04--inner-frames-with-glazing-tape.jpg

Note that the temporary bracing has now been removed, so the two frames are independent and decoupled.


Glass ready to go into the inner-leaf framing:
Attachment:
BRAUS-window-05--first-glass-ready.jpg




Glass raised into position, being held in place by temporary blocks while it is being sealed around the edges:
Attachment:
BRAUS-window-06--first-glass-going-in-2.jpg



View from inside the window cavity before the second pane goes in, showing how the first pane is sealed in place.
Attachment:
BRAUS-window-07--one-pane-in--middle-view.jpg



The other pane going into the outer-leaf frame, once again held temporarily with blocks until sealed and the trim is applied:
Attachment:
BRAUS-window-08--second-pane-going-in.jpg



Finished window, with trim in place, viewed from the outside:
Attachment:
BRAUS-window-10--finished-outside-2.jpg




... and from the inside....
Attachment:
BRAUS-window-11--finished-window-from-inside-4.jpg




That's an alternative method.

Quote:
3. I was interested in putting desiccant in my window setup to avoid condensation buildup but I'm not sure where I can "hide it" so it's not visible. Does anyone have any recommendations for this?
Put it in a thin "tray" that sits in the gap between the two frames, or on top of one of the frames, then cover the tray with black fabric.

You do need to calculate the correct amount of desiccant to use, though. If you don't use enough then you'll still have condensation issues. If you use too much, you run the risk of drying out the wood or the seals.

- Stuart -


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PostPosted: Wed Feb 14, 2018 10:26 am 
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Joined: Sat Oct 07, 2017 10:35 am
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Location: Glenwood, MD
Stuart, thank you SO very much for your response, I really appreciate it. I've uploaded an image (titled "Image 1") that represents the wall that will have the double sided glass. This is the one wall that connects the control room to the iso booth (as depicted in the drawing in my previous post). The right leaf contains the 2 layers of 5/8" drywall (with green glue sandwiched in the middle) and the small gap to the left is the 0.5" space from the resilient channel. The left leaf (the control room side) is the side that only has one sheet of 1/2" drywall. Both leafs are packed with Roxul in between the studs. There is one inch between the stud frames from drywall face to drywall face across the cavity. The studs are not staggered and all of the studs are 2X4's.

The 1/2" drywall was from when the room/house was originally built (I didn't put that up). Now, I could rip down the 1/2" drywall on the CR side and replace it with 2 layers of 5/8" but it would really set me back, time-wise, as I really need to start having clients in to record again. That being said, it sounds like this is my "weak link" and would potentially nullify all of the other work I've done on the other walls....

Every other wall in the iso booth is 2 leaf, with the inside and outside layers containing 2 layers of 5/8" drywall/green glue and resilient channel (the RC is on the iso booth side only). I'm including a picture named Image 2 that shows the entrance to the iso booth, where the door will be that represents all of the other walls with the exception of the wall that will contain the window. Just so I'm clear with what I'm trying to express, with these other walls, also, there is one inch between the stud frames from drywall face to drywall face across the cavity.

Regarding the Green Glue, this is the quote from Rod's book (page 100): "If you are using products like Green Glue between your drywall layers, then it gets a little more involved. In cases where the construction is outside of the norm, you have to take the time to determine the equivalent mass for your window assembly. Products like Green Glue, MLV and special drywall products that include combinations of drywall with special internal damping, all achieve isolation greater than the just the mass of the wall would account for. In those cases, it's important that you determine what the equivalent mass would be and the size of the glazing accordingly".

Your pictures are SO helpful, than you for posting. Are you using aluminum foil tape to adhere the fabric to the box frame? Also, is there an equation to use in order to figure out how much desiccant to include? Lastly (and I apologize for belaboring the point), but I'm still not clearly understanding how to take the information that you provided regarding wall density and use that to figure out how thick each sheet of glass should be. I suppose I'm just not clearly understanding how to determine the surface density of each leaf.

Again, I appreciate you taking the time to respond, thank you again!

Bob


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PostPosted: Wed Feb 14, 2018 10:28 am 
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Location: Glenwood, MD
Image 1 was uploaded as upside down for some strange reason and Image 2 should be rotated 45 degrees clockwise


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