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Double-glazed laminated, or triple-glazed non-laminated?

Discussion in 'Room Acoustics / Studio Design' started by JCurtisDrums, May 16, 2016.

  1. JCurtisDrums

    JCurtisDrums Active Member

    Hi folks,

    I'm building a drum room in my garden, and we are at the stage of deciding on the windows. We are faced with the choice for the outer window with either standard double glazing but with laminated glass panes, or triple glazing with unlaminated panes. The company have stated that the triple-glazed laminate panes would be too heavy and not practical.

    I will be installing a secondary inner glazing of some kind afterwards, but need to decide on the external glazing now. For sound isolation, which of my two options would be preferable?

    The window hole size will be 2100 x 1350 mm.

  2. paulears

    paulears Well-Known Member

    Personally - the size of the glass, and having had experience of what happens when it breaks, makes laminated glass my own preference. Do you have a double skin? If so a double glazed panel on both sides would be pretty good. The only thing to check is to see the supplier and put your chosen panels together and check how much light you lose. Outside, I'd guess they'll just look a bit opaque, just a little 'misty'. My internal glass window from the main room to the drum room is a little lossy and I have laminated on one wall, and it's non-laminated on the drum room side - which works better for communications, and I figured the safe glass on the side I usually sit was best.
  3. Brien Holcombe

    Brien Holcombe Well-Known Member

    Laminated glass is always...always the way to go in an audio environment, works good in vehicles as well. Because of the way the glass is developed, e.g. with lamination between the panes, you get a damping factor that just cannot be imitated by any other means.

    The basics of mass/air/mass as it applies to the acoustics of a room keep in concert with the room construction and the known low frequency losses associated with multiple air space configurations, like a triple glazed window.

    So a laminated glass pane is not only damped by design, it is also thicker per glass pane and is always the better choice over single pane even if it were a triple configuration.

    So you want laminated, you do not want triple panes in either windows or wall construction.

    Hope that helps.
  4. kmetal

    kmetal Kyle P. Gushue Well-Known Member

    Double pane laminate. 2 panes, regardless of glass type.
  5. JCurtisDrums

    JCurtisDrums Active Member

    Brilliant! Thanks everyone, just what I needed.

    paulears: yes, a double layer room. I'm modelling it on the double stud two leaf design from Rod Gervais' book. I'll try and match the laminated double glazing on the inner window too.
  6. Brien Holcombe

    Brien Holcombe Well-Known Member

    See, this is NOT what you want to do. You want to establish a double leaf construction...yes. But you do NOT want to modify this and use double glazing on two different walls...if you do you have designed a multiple leaf, multiple airspace that will have low frequency transmission loss.

    The ONLY way you can have multiple leafs be effective is to have LARGE air space in between the hard boundaries. So if you are developing a double wall assembly (mass/air/mass) then you want one pane laminated on one side of the wall assembly and one pane of laminated on the other wall assembly to produce the highest transmission loss. It is often recommended to use different thicknesses of laminated when you do this type of thing to offset the natural frequency of the two pieces of glass since glass has a higher natural frequency than the typical hard boundaries.

    Somewhere in Rods' book it shows a detailed control room window. Does it use double glazed glass? No...because if it did it would not be the best window type to develop since it would have multiple small air spaces known to produce low frequency loss and low frequency is the area you want your assembly to do the most work at.

    If you read the book it will explain this to you and keep you from making mistakes that on line experts will have you make due to ignorance.
  7. JCurtisDrums

    JCurtisDrums Active Member

    I see. So you're saying that by having double glazing on the inner and outer wall, I'm actually creating a 4 leaf construction, which is less effective. Instead, I want a single laminated window on the inner, and a single laminated (prefereably different thickness) window on the outer to retain a two-leaf system. Is this approach likely to be enough for a drum kit? It seems so little compared to the amount of mass in the walls. Also, is it likely to be more effective than a single double glazed (laminated) window?

    Thanks for your help.
  8. Brien Holcombe

    Brien Holcombe Well-Known Member

    Windows and doors are always the weakest link in an assembly for obvious reasons. If doors are not properly sealed then the door will leak air, and where air goes so does sound. So solid core doors are recommended with super attention to the sealing detail/threshold areas to maintain isolation.

    Windows are different in that you still want to see through the window but you need it to maintain the transmission abilities of the existing wall assembly as much as possible.

    If I recall correctly, the rule of thumb with laminated glass is this. 1/4 inch for a single 5/8 fire-rated sheet of sheetrock and for ever additional sheet of sheetrock installed on the same wall you add 1/8 of an inch to the thickness of the glass to attempt to match the transmission loss or STC of the wall assembly.

    Like if I had a wall assembly with three sheets of 5/8 inch fire rated rock I would recommend the glass on that side of the assembly be (1/4 + 1/8 + 1/8) 1/2 inch laminate glass. Usually the issue is budget as this glass gets expensive as you are already aware. Still, this is what has to be considered or you wind up with a big acoustical hole in the wall that lets sound go in or out depending on the natural frequency of the pane.

    If you would like to have an opinion based on science opinion that supports what it is I have said, in part, please read this document:

    Yes, and I have pictures.

    The physics involved in the determination of the TL or STC of the above assemblies is physics...it will apply to windows as well.

    An over simplification is this. As you develop multiple leaf assemblies(more than 2 leafs) the ability to attenuate high frequency is increased. The assembly has more ability to stop high frequency sound due to mass. But the problem is that as you make all this gain in high frequency, the multiple leaf assembly loses ability to contain low frequency energy. And that is due to multiple "hard" or shallow air spaces that combine resonant frequency of the overall wall assembly.

    Granted STC is not a good method to establish what is or what is not a good value for an assembly, as Transmission Loss is the far better of the two since the TL will show at what frequencies an assembly performs well at, where the assembly is holding it's own and where the TL begins to get weak or lose ability to contain sound energy. In a multiple leaf assembly it is always the low frequency area that the assembly fails at.

    And with drums being a whole lot of low frequency energy, you do not want to develop an assembly that will allow low frequency a way out. But even with piano and the male voice it can be just as bad. Overall you want to always prepare for the lowest frequency when it comes to a music filled environment.
  9. JCurtisDrums

    JCurtisDrums Active Member

    Thank you Brien, your posts are excellent, and extremely helpful. I have seen the picture you provided in Rod's book, but hadn't applied the same logic to the windows. As stated, I have a rather large window (as it will be my main studio and work area, I need natural light in there or I'll go crazy), but I also need it to open. If I get a single glazed laminate UPVC (with openable panel) on both the inner and outer, at the thicknesses you described, is that likely to be sufficient to match the wall construction? Will it be a weakspot in the sound isolation, or will it match the wall? As per your diagram, the wall design we are using is the furthers to the right, the true double-leaf design
  10. Brien Holcombe

    Brien Holcombe Well-Known Member

    OK, well, I think it is time for you to show us some pictures of what it is you are talking about. You are having a fresh air situation that troubles you.
  11. JCurtisDrums

    JCurtisDrums Active Member

    Well here's the sort of thing we've been looking at, standard UPVC windows where you can customise the options. For example, we can select laminated glass, double or triple glazing (although not single, apparently), and the sizes and openings. I need to be able to open the window for fresh-air, that's not really something we can compromise on.


    The best thing going in our favour is the building's distance from the nearest neighbour (30-40ft).
  12. JCurtisDrums

    JCurtisDrums Active Member

    It seems I need a single-pane laminated window on the inner and the outer. Am I right?
  13. Brien Holcombe

    Brien Holcombe Well-Known Member

    Depends on the distance from interior wall to exterior wall.

    I like double glazed on the exterior of any structure for the thermal benefits. But I wouldn't want one inside unless it was one single window.

    It would still be helpful to see where it is these windows are going to make a better decision. Another thing that I couldn't get a handle on was the seals of these windows. Like stated earlier, seals are where you get the most leaks at.

    I would still want a double paned window on the exterior but a single pane on the interior
  14. kmetal

    kmetal Kyle P. Gushue Well-Known Member


    This is an example of a typical looking exterior window, which includes integral seals, and sound rated glass. I think this might be what you have in mind Jcurtis? I've never used this company, but I'm pretty sure it's the same one rod pointed me to at some point. Either way, this Windows aren't cheap, but they look and act the part.

    Exterior windows add the additional thermal requirements to the planning of a window. Whether or not it opens and closes mechanically to the outside world, also determines the design characteristics, air sealing and proper glass thickness are critical.

    Here's the data sheet for that particular window.


    Data sheet for various Pruduct lines from silent guard.


    Here's the brochure.

  15. Brien Holcombe

    Brien Holcombe Well-Known Member

    So how is that, kmetal, any different from what the man is looking at?

    But while you think about that, and the fact he does not live in the continental USA, I have a piece of information from the website you mentioned that may be useful, should you continue to push this kind of data.

    "Silent Guard products are available for direct purchase by builders or dealers only. To order direct from the manufacturer a minimum of 100 units is required."

    So all things being equal, these windows are in no way different from the one the OP is looking to purchase, excepting the ones the OP is looking at are attainable.

    The STC rating is pretty common expectation from 1/4 inch laminated, 33+/-.
  16. kmetal

    kmetal Kyle P. Gushue Well-Known Member

    The links I posted have published sound test data which easily available on the site, the OPs did not (none that I could find at least) that is an important difference right there. Looking the part, isn't always the whole tale.

    Where in my post did I suggest the OP purchase silent guard brand Windows? where did I suggest he order directly through them?

    The 'OP is triple glazed or double glazed?' The data I pushed was simply to explore the types of offerings and the resulting performance according to some numbers.

    How can you verify this brien? Have you installed both brands of these windows and compared the test data you generated? How do they compare price wise?

    If all things are equal, is a big if. Are you familiar with any suppliers? Particularly overseas? What's the availability like relative to its counterpart across the pond?
  17. JCurtisDrums

    JCurtisDrums Active Member

    Thanks for the replies. I am still here, just a bit busy with my playing schedule at the moment. I will try and post a picture of my design plans so you can get a better idea of what I'm talking about. So far, what I've taken from this is to us a laminated double-glazed external window, with a thick, single-paned internal window like the above posted solutions.

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