Site-built window pair, for high isolation.

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Soundman2020
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Site-built window pair, for high isolation.

#1

Postby Soundman2020 » Mon, 2019-Dec-30, 00:11

Site-built back-to-back studio window pair, for high isolation.


A quick photo-sequence on how to build your own isolation window for your studio, and still get good isolation.

These photos come from a client in Australia, who teaches drums in his studio. His neighbor's front door is also just a few meters away from this window, so he needed to get very good isolation. The window design I did for him is not complicated, and he also came up with some good ideas of how to implement it in practice. Theoretical isolation is 55 dB, and is good down to about 30 Hz. (MSM resonance at 15 Hz, predicted). In practice, it's darn good!

This is a companion article to the site built door for high isolation, and uses a simple but very effective design that I have developed for such windows.

This sequence of photos is actually from the same studio as the site-built door, so all the comments there on the level of isolation that we achieved for that, also apply to this window.

The build starts with the construction of the casing, or frame, for the window unit. For this build, there was a need for high isolation, thus thick heavy glass, so the wood has to be rather thick too. The casing is sized to fit within the rough opening in the wall, leaving only a small gap around the sides and top to allow for some maneuvering to get it in, as well as to shim it to get it straight, level, and plumb:
Soundman--Site-Built-Isolation-Window--101--main-outer-frame--BRAUS--Soundman2020--recording-studio-Design.jpg


Similar to the way the door casing was done, here too a pair of frames are temporarily attached to each other with blocks, to keep them the correct distance apart. When placed into the rough opening, one of these frames will be in the inner-leaf wall and the other in the outer-leaf wall. Once they are firmly attached in place, the blocking is removed, and they become separate, but spaced. Not that black cloth has been wrapped around the frame, over the gap between them, and has also be glued and taped in place. This hides the small gap between the frames, so you can't see through the gap into the ugly interior of the wall.
Soundman--Site-Built-Isolation-Window--102--both-outer-frames-cloth-and-tape--BRAUS--Soundman2020--recording-studio-Design.jpg



In the next image, the pair of frames has been presented into the rough opening, and is in the process of being shimmed, to get it level and plumb, and check that the corners remain perpendicular to each other (90° angles), to ensure a tight, clean fit for the glass and seals. Note that the two frames are still connected by the temporary bracing, until they are both shimmed together, to line up perfectly:
Soundman--Site-Built-Isolation-Window--103--both-outer-frames-in-place--BRAUS--Soundman2020--recording-studio-Design.jpg



Next up: the frames have been fixed in place, and the temporary blocking removed. The backer blocks have also now been attached. Those are the thick wooden strips you can see in there, around the perimeter of the casing. The glass presses up against those, and they keep it in place. The white tape on the front face of the backer blocks is glazing tape. It's a double-sided adhesive foam tape that sticks to the blocks at the back, and the glass on the front, creating a good seal between the glass and the wood, and holding the glass in place. I sometimes also use rubber strips there, instead of glazing tape, to do the same job but without the adhesive.
Soundman--Site-Built-Isolation-Window--104--inner-frames-with-glazing-tape--BRAUS--Soundman2020--recording-studio-Design.jpg



Now the glass itself is ready to go in. You can see how thick it is! This is laminated glass, and for this project (a drum teaching studio), high isolation was a key issue, so thick laminated glass was needed. Here, a wooden beam has been set up to support the glass just in place, just before it is raised, to it can be cleaned. You need a lot of hands to raise that glass, as it is heavy, fragile, and dangerous. However...you have to be careful here! Those "hands" need to be clean, and wearing cotton gloves for installing the glass... once it is in place, it is impossible to clean the side that faces the wall cavity... and you don't want fingerprints, smudges, or dirty marks stuck in there forever, messing up your view.... so you need to clean that glass perfectly just before it goes in, then handle it very cleanly as you put it in place. The side facing the room is fine: that can get smudged and dirty, as you can access it later for cleaning.. but the side that faces the cavity is "forever". So clean it carefully, and inspect it carefully, and use clean cotton gloves when you touch it to raise it. You will also need some type of desiccant to put in the gap between the window panes, to adsorb any moisture in the trapped air. If you don't do that, then the glass can fog up on the inside surfaces under some climate conditions, and perhaps even have condensation droplets forming on the surface, then running down the glass... leaving permanent dirty marks! So it's important to get the desiccant in. Silica Gel is good, and there are other types to. You need to calculate how much to put in. It's not a lot, and it's not expensive, but you do need to get the amount roughly right: too much could potentially cause the wood to dry out excessively, and not enough means... well.. misted windows with condensate tracks! I don't have photos of the desiccant going in, unfortunately. We missed that here.
Soundman--Site-Built-Isolation-Window--105--first-glass-ready--BRAUS--Soundman2020--recording-studio-Design.jpg


Here the glass has been raised into position, up against the glazing tape, and is being held in place with some more temporary bracing while the front blocking goes in, and the caulking is done.
Soundman--Site-Built-Isolation-Window--106--first-glass-going-in-2--BRAUS--Soundman2020--recording-studio-Design.jpg



This is a view from the other side, taken in the middle of the frames, showing how it looks after a bead of clear caulk has been placed around the rim where the glass meets the backer blocks. Applying that caulk is a very tricky job, as you do not want to get marks and smudges on the glass as you work, and you also want a clean, smooth, even bead, so it looks good. The reason for the caulk is to have an extra seal: for high isolation, never trust just one seal. Even though the glass is resting in glazing tape (one seal), pressed up against more glazing tape on the front face of the backer blocks (seal #2), and will have yet more glazing tape on the front trim blocks (seal #3), I also like to caulk the glass to wood joints hear (seal #4) and on the front as well (seal #5). Of course, you can't really caulk the back of the other pane when it goes in on the outer leaf, so that one can only get 4 seals, but the inner one has 5 seals. The caulk also has much more mass than the glazing tape, so it helps to keep the mass consistent across the entire leaf.
Soundman--Site-Built-Isolation-Window--107--one-pane-in--middle-view--BRAUS--Soundman2020--recording-studio-Design.jpg



Now the second pane of glass goes into the other frame, on the outer leaf. Once again you can see the temporary bracing holding the glass in place while the front rim blocks are added, and you can also see that this pane is sealed in with rubber, not glazing tape. This is an external window (faces the wind and the rain), so it needs something more substantial than glazing tape to resist the elements better. It also can't be caulked on that inner face, so no extra mass from the caulk. But rubber has plenty of mass. So this side is a bit different: rubber, instead of glazing tape, for the seals. Apart from that, the same process was used to raise it into place, and hold it there until everything is finished.
Soundman--Site-Built-Isolation-Window--108--second-pane-going-in--BRAUS--Soundman2020--recording-studio-Design.jpg


A view of the final finished window from the outside, with the front blocking and trim in place.
Soundman--Site-Built-Isolation-Window--109--finished-outside--BRAUS--Soundman2020--recording-studio-Design.jpg



Another view from the outside, showing he complete window. (The marks are on the outside of the glass, not the inside).
Soundman--Site-Built-Isolation-Window--110--finished-outside-2--BRAUS--Soundman2020--recording-studio-Design.jpg



And finally, the finished window from the inside, with all the blocking and trim in place, and the wall also completed (the wall is built "inside out" in this case):
Soundman--Site-Built-Isolation-Window--111--finished-window-from-inside-4--BRAUS--Soundman2020--recording-studio-Design.jpg
.

So, there you have it! A very simple method for building and installing a site-built high-isolation window. As I mentioned above and in the article on the doors, the total isolation for this studio is around 55 dB. The studio owner teaches drums, so he sometimes has two drum kits going at once in there! Hence, the need for good isolation. As you can see, it is possible to attain these high levels of isolation even when you build your own window, if you do it carefully and based on a good design. It's also a LOT cheaper than buying a commercially made studio isolation window!


- Stuart -



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Marius
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Site-built window pair, for high isolation.

#2

Postby Marius » Fri, 2020-Apr-03, 20:58

I love the detail in this! Great job. ¡ Muy Rico !

What are the dimensions of your Window ?

How thick was each glass?

Marius Perron
Texas



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#3

Postby Soundman2020 » Fri, 2020-Apr-03, 21:20

Hi Marius, and welcome to the forum! :thu:

I'd have to check the project.... it's been a few years since we did that place. I¿ll need to pull out the backups and check... stay tuned!

- Stuart -



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#4

Postby Soundman2020 » Fri, 2020-Apr-03, 21:31

Well, that was a bit quicker than I thought it would be! I found an early draft on my computer, so I didn't need to go find the backups...

The original design says: "1130mm wide x 930mm high, 16mm thick (6mm+10mm, laminated with acoustic PVB)", but I seem to remember that we increased the thickness of the glass later, to 20mm (10+10). I noticed you are in the USA, so the equivalent measurements would be roughly 40-1/2" wide, 36-5/8" high, and 1/4" + 3/8" (original) thickness, or 3/8"+3/8" (final) thickness, give or take a few 1/64ths in each case!

Oh, and cavity depth (distance between the panes) is around 13" (330mm).

- Stuart -



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Site-built window pair, for high isolation.

#5

Postby killerjoe » Sun, 2020-Apr-12, 02:53

Was the glass laminated together on site? I thought it was a heat process that can only be done at the glazier's factory?... I have plenty of 10mm glass that I'd love to put together back to back to create 20, or even 30mm thickness. Can I just push them together without anything in between, or is there a way to place thin PVC sheets between the panes without heat treatment? Double sided sticky film?



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#6

Postby Soundman2020 » Sun, 2020-Apr-12, 03:25

killerjoe wrote:Source of the post Was the glass laminated together on site? I thought it was a heat process that can only be done at the glazier's factory?...
The glass was order with those dimensions. Unfortunately, it isn't possible to laminate glass yourself. As you mentioned, it has to be done at high temperatures and pressures, in a carefully controlled environment. Also, you can't cut laminated glass: it has to be ordered to spec, or purchased as a standard size. (Well, you can cut it, but it requires specialized tools, skill, and is dicey)

Can I just push them together without anything in between, or is there a way to place thin PVC sheets between the panes without heat treatment?
It's not PVC: it's PVB. Polyvinyl Butyral. It's a resin that comes in thin sheets on a roll, and needs the high temperatures and pressures to properly bond the glass panes together.

I'm not aware of any way of sticking glass panes together yourself. I suspect that it would not work very well: even if you could find some type of sticky film broad enough for your windows, you'd probably end up with fingerprints, dust, hair, air bubbles and other nasty stuff, permanently embedded in your windows. The lamination process for laminating glass is done in a clean room, with everyone wearing head-to-toe suits, to prevent that type of problem. I don't think that it would be possible to do it as a DIY project. I might be wrong and maybe there is a way of doing that, but I've never heard of it. It's a lot easier to just buy the laminated glass.

On the other hand, if you have panes of ordinary 10mm float glass, you could still get reasonable isolation with two windows using that, if the air gap between them is big enough. It won't be as high as we got with this design, of course, but it might still be sufficient for your needs. Probably in the low to mid 40's (decibels transmission loss). Have you figured out how much isolation you need for your studio?


- Stuart -



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#7

Postby killerjoe » Sun, 2020-Apr-12, 11:16

Well, the walls will be 80kg/m2, so the window and doors need to be commensurate. How about 3 (loose) panes touching each other? What's the worst that can happen?

Or even more controversially, with tiny gaps in between them (1 - 2 mm). Yes, I know that triple and quadriple leaf can compound resonance issues, but I had a quadriple window at my last studio and it worked fine. But the gaps were < 100mm ...



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#8

Postby killerjoe » Mon, 2020-Apr-13, 12:40

.... or would this work just as well?

Studio Window Detail.png


Would these gaps (120mm and 150 mm) create a 3 leaf affect ? Which resonances? How would this window compare TL wise to the rest of the wall? If this window won't suffice, what would? Is there any way I can use all my 10mm lam glass to construct an effective window?



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#9

Postby Marius » Tue, 2020-Apr-14, 13:20

Hey there Killer Joe –

In your drawing you have an “External Glass Façade”. Are these windows to the outside of your building? That will bring in light from the outdoors? I am planning the same thing !

What is your “External Glass Façade” ?

I am in Texas and the architect was saying that the external window has to “meet code”. At that we couldn’t just build something onsite – we must use a prefab window that has been tested and has a particular “R” value…



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#10

Postby Soundman2020 » Tue, 2020-Apr-14, 14:03

Marius wrote:Source of the post I am in Texas and the architect was saying that the external window has to “meet code”. At that we couldn’t just build something onsite – we must use a prefab window that has been tested and has a particular “R” value…
It sounds like he's talking about some type of curtain wall? It is possible to integrate that into a studio, yes, but there are issues that will need special attention, from the point of view of isolation. Also, having entire walls of glass in a studio can be a bight of a nightmare! All those reflections...

- Stuart -



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#11

Postby Soundman2020 » Tue, 2020-Apr-14, 14:45

killerjoe wrote:Source of the post Would these gaps (120mm and 150 mm) create a 3 leaf affect ?
Yes, with caveats: If that outer glass facade is a curtain wall in a commercial building, in many cases the glass is not sealed to the floor or ceiling, so you don't have good isolation.

Which resonances? How would this window compare TL wise to the rest of the wall?

Assuming that the above is not the case, and your outer-leaf glass is sealed such that you have a "classic" 3-leaf system, then in theory the F+ and F- frequencies for that would be around 43 and 31 Hz, respectively. So isolation would start at around 60 Hz, upwards. Overall isolation would be around 50 dB.

That's for the window. For the combination of the rest of the system (2-leaf), the figures would be: F0=36 Hz, isolation=about 52 dB. So the overall window isolation would roughly match the overall wall isolation, but the window would have an isolation dip around 45 Hz, due to the 3-leaf effect.

If this window won't suffice, what would?
Higher density glass. For example, replacing each of your 10mm panes with 20mm laminated glass panes, would drop F+ and F- down to 33 and 24 Hz, and isolation would improve to about 55 dB. In this case, the window would actually be slightly better than the wall.

But there's another issue with the "window box" itself: as shown in your diagram, the two glass panes are coupled to each other through the MDF casing. That's a flanking path, which would reduce isolation. You could fix that to a certain extent by carefully decoupling and "floating"
each of those panes on soft rubber strips all around the perimeter.

The big question here, is: how much isolation do you need for your studio? And the associated question: What frequency range do you need to isolate?

- Stuart -



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#12

Postby killerjoe » Tue, 2020-Apr-14, 23:25

Marius wrote:Source of the post Hey there Killer Joe –

In your drawing you have an “External Glass Façade”. Are these windows to the outside of your building? That will bring in light from the outdoors? I am planning the same thing !

What is your “External Glass Façade” ?

I am in Texas and the architect was saying that the external window has to “meet code”. At that we couldn’t just build something onsite – we must use a prefab window that has been tested and has a particular “R” value…

It's a curtain wall, well sealed. I know it's lam glass and was hoping it would be 12mm, but the building plans seem to refer to a measurement of only 8mm lam for the windows. This seems a little thin to me, but hopefully the 80kg/m2 walls on the inside will help 8-)




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