Hiya Juajar,

You are correct that the difference in STC from 43 to 35 is significant. Many (most?) authorities consider a difference of 10dB to result in halving "loudness" thru a partition.

I am puzzled why the IG make-up uses 4mm and 5mm glass though. Changing to 3mm / .762pvb / 3mm / 10mm airspace / 3mm / .762pvb / 3mm likely results in both improved energy and sound performance versus the 4mm IG.

I say likely because while I don't have either of the make-ups that you listed in my references, I really think that the IG STC as listed in your post is too low.

Using a 6mm airspace in option 2 is not helpful for sound performance, in fact I would suggest that it's even detrimental to the inherent advantage of using two laminated lites in the make-up, but I have trouble accepting that it could drag the STC down to 35. I would be anticipating an STC of maybe 40 or so based on the construction you listed.

Since you live in a very mild climate you might be perfectly comfortable using the triple lami, but if it were for me I would be looking into using the thinner glass and wider airspace in the IG for both sound and energy performance before making my final decision.

Thanks Oberon for your explanation. Its curious that you mention the low STC for option 2 as that is exactly what the person who came to my house said. He was confident there had to be something wrong with the STC measurement from option 2. His exact words were "There might be a slight difference between the STC's, but it would probably be around 2 or 3"... If this were the case, then is 2 or 3 STC points really worth getting the triple laminate without any insulation?

What would be your opinion in terms of durability, I'm worried about the weight of the triple laminated (18 mm thick glass in relatively large windows) vs option 2....

Last, I thought it was better to have different widths for the two panels, in your 3+3+10+3+3 wouldn't these be affected by being simetrical? Do you think this config would preform better or worse vs the 4+4+6+4+5 config?

Thanks again!

The trick with STC is it doesn't take into account noise outside of the standardized range (125-4000hz) OITC is a better indicator in the case of road noise since it has a better range of consideration.

Even then, you still have to deal with the actual blocking capabilities in specific ranges. If all of your noise is 50-100hz, you don't care about 3500hz, which could be where one window has all of its blocking strength.

The two different thicknesses of glass on the inside of the second window will change the frequency range at which the window blocks (one pane blocks frequency range a, second is now tuned differently and blocks a different one). This is probably why it may seem more quiet, and the thicker one will block a lower frequency range.

What I don't understand is why are you saying IG? Aren't both of those options laminated? You are just talking about looking at a triple pane window where every pane is laminated vs a double pane window where both are laminated?

I might be missing something in your description unfortunately. Do you have a copy of the actual STC reports from those two windows? That could tell a good tail about which is optimal in your situation.

Thanks Scot!! I do have a copy of the reports, I am attaching them to the post (Sorry they are in Spanish... If you ned anything translated drop me a line).

Do you have an opinion re. Durability?

Thanks

Option 1 STC:

Option 2 STC:

So if you are looking at road noise, the first window is better, by a minimum of around 3db, across the range that matters.

Is that worth the added cost? Can't say, you need to determine that. What I can say is that 3db is significant. If you are sitting right next to your windows, it might not amount to a heck of a lot, but if you move back a few feet it would be audible. That is small enough for a bad install to make it a moot point.

Also, as pointed out by some of the experts here to me, air leakage will negate a lot of the benefits of a nice STC. If the window choices have a difference there, you should include that in your assessment.