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Studio windows and glass thickness
Old 18th September 2020
  #1
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Studio windows and glass thickness

Hi.

I'm in the midst of a studio build and just thinking about the windows. The building has double glazing (4mm - 14mm gap - 6.8mm) and I was going to then add secondary glazing on the inner wall. Just a couple of questions.......

1) If I add the secondary glazing will I be creating a triple leaf and therefore making sound isolation worse than if I just had the standard double glazing window.
2) If it is still beneficial to add secondary glazing, what thickness should it be? They offer 4mm / 6mm or 6.8mm. Would 6mm be different enough from the 6.8mm in the existing window to negate any resonant frequency issues?

Any advice appreciated

Thanks!

Chris
Old 18th September 2020
  #2
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Kyle P. Gushue's Avatar
To compensate for 3 leaf situations you can

1. Make the air gap large enough that the 3rd leaf is not longer an issue.

2. Make the 3rd leaf massive enough to not be an issue

What your interested in is the density of the glass not the thickness.
Old 18th September 2020
  #3
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Thanks Kyle. The maximum air gap I can achieve is about 125mm. Any idea how I'd calculate the density of glass needed? Most of the secondary glazing units I've seen are around 7-12mm which I realise isn't particularly thick.

Basically wondering if I'm better off leaving double glazing as is or is there a marginal gain from adding secondary glazing. Obviously don't want to do it if it's going to be detrimental.


Just for info, the rest of the room is constructed as below:

Walls: Double layer of 15mm Acoustic plasterboard with Green Glue between on isolated wooden studs with 100mm insulation between the studs. There's then an air gap of about 50mm and then brick outer walls (9" thick). The ceiling is the same construction (2 layers of 15mm board+ GG, hanging from their own joists)
Old 18th September 2020 | Show parent
  #4
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by C247 View Post
Thanks Kyle. The maximum air gap I can achieve is about 125mm. Any idea how I'd calculate the density of glass needed? Most of the secondary glazing units I've seen are around 7-12mm which I realise isn't particularly thick.

Basically wondering if I'm better off leaving double glazing as is or is there a marginal gain from adding secondary glazing. Obviously don't want to do it if it's going to be detrimental.


Just for info, the rest of the room is constructed as below:

Walls: Double layer of 15mm Acoustic plasterboard with Green Glue between on isolated wooden studs with 100mm insulation between the studs. There's then an air gap of about 50mm and then brick outer walls (9" thick). The ceiling is the same construction (2 layers of 15mm board+ GG, hanging from their own joists)
Its density, not thickness that's key. Different types of glass ie float vs laminate, have different density, despite the same thickness. Its about mass.

Youve got a nice amount of mass and decoupling in your assembly, and the windows need to match or exceed that level of performance, to not be a weak link. There is an equation i can dig up to calculate less massive sections of a wall if you need it.

Ive never had to calculate a 3 leaf assembly, but the wyle report (attached) does show how if your inclined to do so. Otherwise it should be pretty short work for a full time acoustician.

Ill assume you want to keep the window, so i wont delve into window plugs ect, which are an option.

You have to make sure that the window assembly is completely air tight. Soundproofwindows.com is well liked, and might be able to help you.

This thread might help.

Exterior Windows - Prefab ?
Attached Files
File Type: pdf Wyle WR 73-5R.pdf (11.69 MB, 13 views)
Old 18th September 2020
  #5
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Thanks Kyle. That's really helpful.

Best
Chris
Old 18th September 2020 | Show parent
  #6
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by C247 View Post
Thanks Kyle. That's really helpful.

Best
Chris
i edited the post while you were responding. These threads might help you.

Exterior Windows - Prefab ?

3 Leaf Effect for windows...
Old 18th September 2020
  #7
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avare's Avatar
 

The panes are so close they almost act as single pane of total mass. Slightly paraphrasing Kyle go for for the deepest and thickest, Laminated would give additional isolation

The triple leaf equations in a slightly more legible form are in Vinokur (attached) and Long Architectural Acoustics. Vinokur fig. 7 shows the similarity closely spaced panes.
Attached Files
Old 18th September 2020 | Show parent
  #8
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by avare View Post
The panes are so close they almost act as single pane of total mass. Slightly paraphrasing Kyle go for for the deepest and thickest, Laminated would give additional isolation

The triple leaf equations in a slightly more legible form are in Vinokur (attached) and Long Architectural Acoustics. Vinokur fig. 7 shows the similarity closely spaced panes.
Thanks again for yet another amazing resource!

How would one determine if the leafs are close enough together they act almost like a single mass, or far enough apart that the resonance is low enough that the 3 leaf situation isn't an issue?

In these cases, would you use the calcs for MAM or still use 3 leaf math, when adding the additional leaf?

Sorry if im muddying the thread.
Old 18th September 2020 | Show parent
  #9
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avare's Avatar
 

Quote:
Originally Posted by Kyle P. Gushue View Post
Thanks again for yet another amazing resource!

How would one determine if the leafs are close enough together they act almost like a single mass, or far enough apart that the resonance is low enough that the 3 leaf situation isn't an issue?

In these cases, would you use the calcs for MAM or still use 3 leaf math, when adding the additional leaf?

Sorry if im muddying the thread.
About an inch. See LONG Architectural Acoustics chapter 9 or more information.

There is no generalization for not using the proper equations when I am working for a client. For related information read Canadian Builders Digest CBD-240 and note figures 3 and 9.
Attached Files
File Type: pdf CBD-240.pdf (1.89 MB, 11 views)
Old 18th September 2020 | Show parent
  #10
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by avare View Post
About an inch. See LONG Architectural Acoustics chapter 9 or more information.

There is no generalization for not using the proper equations when I am working for a client. For related information read Canadian Builders Digest CBD-240 and note figures 3 and 9.
Thank you, i will read both.
Old 18th September 2020
  #11
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I use SoundFlow and even with professional software there is some uncertainty and you really need to know the limits of the software. The formulas from the papers Andre posted need to be carefully used. They are not that accurate.

Please read...

http://www.insul.co.nz/media/21198/1412hora.pdf
Old 18th September 2020 | Show parent
  #12
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Kyle P. Gushue's Avatar
Quote:
Originally Posted by andrebrito View Post
I use SoundFlow and even with professional software there is some uncertainty and you really need to know the limits of the software. The formulas from the papers Andre posted need to be carefully used. They are not that accurate.

Please read...

http://www.insul.co.nz/media/21198/1412hora.pdf
I read that paper a while ago, i was actually looking for it recently but forgot its title.

Have you done triple glazing estimates with soundflow? It would be interesting to compare them to test data in the CBD and Vinokur papers.

If the computer models are limited, and math not that accurate, then how do we asses these situations?

Ive only ever used double glazed windows, and just used a mass based approach. The triple glazing scenario seems to require more than that.
Old 19th September 2020 | Show parent
  #13
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I am not saying math is not accurate,I am saying there are limits and you need to be aware of them.

You do what the paper does, you test these formulas and software against configurations that have been tested in the lab.

What is the problem with studio recording situations ? When you want to test a partition that has at least 70 dB reduction you rarely have lab measurements for those situations.

Usually what happens with these formulas or software, they overestimate the Rw-STC values for very high soundproofing values (at least SoundFlow does). So you need to be careful when you use them.

They probably work fine for a glass configuration with 40-50 dB reduction.

I have not yet tested triple glazing configurations with Soundflow since I use tested lab solutions for my client's projects and they are all double glazing.

Quote:
Originally Posted by Kyle P. Gushue View Post
I read that paper a while ago, i was actually looking for it recently but forgot its title.

Have you done triple glazing estimates with soundflow? It would be interesting to compare them to test data in the CBD and Vinokur papers.

If the computer models are limited, and math not that accurate, then how do we asses these situations?

Ive only ever used double glazed windows, and just used a mass based approach. The triple glazing scenario seems to require more than that.
Old 21st September 2020
  #14
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Thank you all for the advice. I've found company who can do me a thick laminated single pane so that looks like it might be a good option for the secondary glazing. I'll then get as much gap between the two sets of windows as possible.

Can I just ask how I seal the between the two sets of windows? I've got a carpenter who's going to make me a frame / box that fits into the decoupled wall and the secondary window will sit within the box. I obviously don't want to attach the back of this box to the brick outer wall as that would bridge my two walls but am I right in thinking that the reveal between the two windows should be airtight?

What if I brought the window box to the brick wall but allowed a small gap (10mm?) I could then add backer rod into the gap and caulk the join. Would this be suitable? If not, any other ideas? Also, should the gap between the windows be insulated around the edges with something like this?

https://www.customaudiodirect.co.uk/...-reveal-liners

Many Thanks again!

Chris
Old 21st September 2020 | Show parent
  #15
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avare's Avatar
 

Quote:
Originally Posted by C247 View Post
Thank you all for the advice. I've found company who can do me a thick laminated single pane so that looks like it might be a good option for the secondary glazing. I'll then get as much gap between the two sets of windows as possible.

Can I just ask how I seal the between the two sets of windows? I've got a carpenter who's going to make me a frame / box that fits into the decoupled wall and the secondary window will sit within the box. I obviously don't want to attach the back of this box to the brick outer wall as that would bridge my two walls but am I right in thinking that the reveal between the two windows should be airtight?

What if I brought the window box to the brick wall but allowed a small gap (10mm?) I could then add backer rod into the gap and caulk the join. Would this be suitable? If not, any other ideas? Also, should the gap between the windows be insulated around the edges with something like this?

https://www.customaudiodirect.co.uk/...-reveal-liners

Many Thanks again!

Chris
Congratulations and yeas and yes! You can leave smaller gaps. 5 mm to fill with acoustic caulk and backer rod. Yes reveal treatment will be of value.

Enjoy
Old 21st September 2020
  #16
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Thanks. Great help!

Chris
Old 24th September 2020 | Show parent
  #17
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Quote:
Originally Posted by avare View Post
Congratulations and yeas and yes! You can leave smaller gaps. 5 mm to fill with acoustic caulk and backer rod. Yes reveal treatment will be of value.

Enjoy
Sorry one last follow up on this if you don't mind.

I can source either a 12.8mm or 16.8mm laminated glass panel on the inner leaf secondary glazing. The 12mm is quite a bit cheaper though as it's a more standard product for the supplier.

I've calculated the mass needed to equal the inner wall composition (2 x 15mm gypsum board) and the 12mm panel is sufficient but not sure how to work out (and therefore avoid) any resonance issues from having the thicknesses off both windows too similar.

The current double glazed outer window is 4-14-6.8mm so would I treat that as one panel (10.8mm - in which case the 12.8mm panel might be too close) or do I treat it as 4 vs 6.8 vs 12.8 in which case it would probably be fine. Or does it not matter as they'll be an air gap of 125mm between the windows negating any issues.

If the 16.8mm panel is going to avoid any issues then I'm happy to spend the extra.

Sorry, just trying to wrap my not particularly scientific brain around this!
Old 24th September 2020 | Show parent
  #18
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Quote:
Originally Posted by C247 View Post
Sorry one last follow up on this if you don't mind.

I can source either a 12.8mm or 16.8mm laminated glass panel on the inner leaf secondary glazing. The 12mm is quite a bit cheaper though as it's a more standard product for the supplier.

I've calculated the mass needed to equal the inner wall composition (2 x 15mm gypsum board) and the 12mm panel is sufficient but not sure how to work out (and therefore avoid) any resonance issues from having the thicknesses off both windows too similar.
You do not have insulation between the panes. Get the thicker laminated glass.

Quote:
The current double glazed outer window is 4-14-6.8mm so would I treat that as one panel (10.8mm - in which case the 12.8mm panel might be too close) or do I treat it as 4 vs 6.8 vs 12.8 in which case it would probably be fine. Or does it not matter as they'll be an air gap of 125mm between the windows negating any issues.
You can calculate with hem being one pane.

Quote:
Sorry, just trying to wrap my not particularly scientific brain around this!
Note you are getting the answers as my first response.

Do not forget to treat the reveal.

Enjoy!
Old 26th September 2020
  #19
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Thanks!
Old 21st October 2020
  #20
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so would 1/2" tempered glass be better than 1/4" laminated?. My exterior window is a dbl pane residental window which I am going to assume are 1/8" each with gas between. My air gap between the exterior window and the new glass is about 8".
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