John Sayers' Recording Studio Design Forum Archive

My question is about studio window glass thickness and type. I'm building a window with two panes, separately mounted as recommended, one piece 1/4, one piece 3/8th. I'll explain the construction around the window, and then get to my question:

I have double walled construction between my control and tracking rooms. One side light weight steel, one side wood. The tracking room has two layers of 5/8 rock, the CR just one. Rockwool in between. The inside distance between the walls is about 16 inches. so I have a rather large air space. I've been researching glass, and window techniques here. there are a couple of things I'm not clear on.

first: Tempered vs laminate glass. I've seen it recommended both ways. Tempered seems to be cheaper here, but that really depends on the particular place I call. Is laminate better?

Second: since I do have a rather big air space, can I get away with thinner glass, which is significantly cheaper? I'm looking at around 215$ right now for a piece of 3/8 and a piece of 1/4. That is in Tempered. If I go to laminate, can I go down in thickness? john's recommendations over at the sae page doesn't seem to specify type of glass, and I see people here are using all kinds.

I hope this was clear. basically, is laminate better, and can I use thinner glass because I've got a big air space without hurting my isolation too much?

thanks
David

basically, is laminate better, and can I use thinner glass because I've got a big air space without hurting my isolation too much?

Laminate is better. It gives typically 3 dB greater TL at higher frequencies. In my neck of the woods, laminate is about twice as expensive as plate for a given thickness.

The last question is your call. The wall system you described has an STC of 46, being limited by the coincidence dip around 2.5 kHz, with TL of around 24 dB@50 Hz. The window system with the panes you detailed with a 14" gap has a STC of around 51, with TL of 25@50Hz. In other words the wall and window are a good match for each other.

Transparently;
Andre

Andre, I'm not sure how you calculated the wall, but this is what I got using the Insul demo - I always change panel size to a more realistic 1.2 x 2.4 meters. I also used 400mm air gap (16") - I agree that the glass being considered is least thickness - I tried using 4.5mm and 6mm glass with same air space and panel size, and it dropped TL @ low end by about 6 dB - NOT a good thing.

What values did you use when calculating the wall, or is there a tested one that matches that somewhere?

David, much as it pains me to say this I would NOT decrease the glass thickness - your low end TL is pretty closely matched this way, and that will make more difference than the mids/highs in most cases... Steve

Andre, I'm not sure how you calculated the wall, but this is what I got using the Insul demo - I always change panel size to a more realistic 1.2 x 2.4 meters

Thanks Steve for catching that. I used Insul demo also, but forgot to change it to double stud.

Thanks for the tip of adjusting panel size also.

How do you get those window shots posted? I think that is great.

Gratefully;
Andre

AVare wrote:How do you get those window shots posted? I think that is great.

Hi!

On your keyboard press the 'Print Screen' button. That copies it to the clipboard so that you can paste it into any image editing program... If you hold ALT and press it it only copies the active window, otherwise it's the whole screen.

Wow, what an uninteresting first post here

MichaelM wrote:

AVare wrote:How do you get those window shots posted? I think that is great.

Hi!

On your keyboard press the 'Print Screen' button. That copies it to the clipboard so that you can paste it into any image editing program... If you hold ALT and press it it only copies the active window, otherwise it's the whole screen.

Wow, what an uninteresting first post here

Thanks.

Maybe uninteresting to you, but to me very helpful. Think of it this way, many of the initial posts here are simple to us acousitcs geks, but to tthe poster, and many readers incredibly useful.

Welcome to the forum!

Andre

Ha yeah thanks.. I didn't mean it like that - It's just I've been sitting at my computer all day doing uni stuff and have kinda had enough of them.

OK, new guy's 'splained another of my (not very) secrets, here's another - if you click on Material Constants, and change density from 690 to 2100, then one inch of "gypsum" equates to 1 inch of concrete - I tracked this from specs on solid concrete walls, and it tracks within 1-2 dB - so you can use one leaf as 6" concrete, and do the other leaf as 2 layers of 15mm gypsum, and get a good idea of performance on a totally different wall structure.

Now, if it would just let us change the insulation, or calculate a triple leaf wall, or.... Steve

Hi guys,
thanks for the explanations of the transmission loss- I'm planning on going with the laminate. here is the problem. Everyone here tells me it only comes in 7/32 - the width of auto glass. I can get tempered glass in anything I wnat, but nobody knows about the laminate. Has anyone run into this problem?
I'm in Seattle, btw..

Thanks again
DAvid

Davidlavin wrote:Hi guys,
thanks for the explanations of the transmission loss- I'm planning on going with the laminate. here is the problem. Everyone here tells me it only comes in 7/32 - the width of auto glass. I can get tempered glass in anything I wnat, but nobody knows about the laminate. Has anyone run into this problem?
I'm in Seattle, btw..

Thanks again
DAvid

Great stuff. I am somewhat surprised by the problem with laminated glas. In my area, I can get just about anything I want in thickness because the lamination is done by the factory on an order basis.

Bearing in mind that laminated glass is 2 to 3 times the price of plate glass, and that you wrote in your first post about trying to reduce costs, why are you thinking of using laminated?

Here is a shot of a window system with 3/8 and 1/2" plate glass. The LF TL is excellent. It would be much cheaper than laminated.

Jumping for a moment, when you build your window, be certain that the panes are supported by the wall studs and not hanging over unsupported.

Transparently;
Andre

ok, I guess I was confused. I thought those breakdowns you and knight were showing me were for the laminate...

A terminoligy question: plate glass and tempered glass. Plate is cheaper yet than tempered, is there any reason I'd want tempered other than safety? I keep saying tempered and you guys keep saying plate. Different, right?


Thank you SO much for the help and clarification guys.

I'm really excited to start building this thing. and yes, definitely I'll be putting the panes directly over each wall.
David

A terminoligy question: plate glass and tempered glass. Plate is cheaper yet than tempered, is there any reason I'd want tempered other than safety? I keep saying tempered and you guys keep saying plate. Different, right?

Tempered glass give better isolation for any given thickness. I don't have sufficient data to calculate how much thinner you could go with the glass if you went tempered. The advantages would be lighter glass so easier to handle, and less strong support needed. The disadvantage would be cost.

definitely I'll be putting the panes directly over each wall.

Synonyms are considered good in english literature, but can be disasterous in technical communication. I wrote "over the studs." All that weight over the gypsum could cause it to crumble and eventually have the glass fall down. I hope that was clear.

Good luck!
Andre

yeah, synonyms...
So basically if I get tempered in the same thickness, I might have a bit better isolation. and it'd be easier to handle? Out here, I'm finding some tempered glass for almost the same price as plate. But I get it now. Thanks

I will certainly be building the window so the glass goes over the studs. So far I feel pretty confident about the design of the windows ( basically using John's from the sae diagram). I may have some more specific questions about that once I get into it, but so far so good. Thanks for answering the glass questions. This has helped immensely.

David

Andre, what source do you have that claims tempered beats plate glass? The only things I've seen claims that laminated is better than the other two; from what I've seen, the only reason for tempered over float plate is safety (which is very important; who'd want giant shards of heavy glass coming at you if a door knocks a mic stand counterweight into a window?)

David, the demo program we've been showing is pretty crippled, and an older version than the ($1000+) full version; it only does float plate glass, and for walls only gypsum (without cheating, that is) and only light weight insulation in walls... Steve

Andre, what source do you have that claims tempered beats plate glass? The only things I've seen claims that laminated is better than the other two; from what I've seen, the only reason for tempered over float plate is safety (which is very important; who'd want giant shards of heavy glass coming at you if a door knocks a mic stand counterweight into a window?)

I don't recall off hand. I will try and dig it up. Thinking anout it right now, it makes no sense.

Andre