Will new windows stop my neighbours being noisy?

Only partly, and less than you would like. Speech and television carry a lot of middle and high frequency, which glazing handles reasonably well. Bass and footfall travel through the structure of the building rather than through the air, and no window touches that.

Is secondary glazing ugly?

It is more visible than a replacement window, and that is the honest trade-off. On a period property it is often the only permitted option in any case, and a slim aluminium system mounted to the existing reveal is far less intrusive than the systems people remember from the seventies.

What should I actually write on the enquiry?

Say that noise is the priority, not heat, and ask for a quotation for asymmetric acoustic laminated units with the leaf thicknesses stated. If an installer responds by quoting triple glazing without addressing the question, you have learned something useful about them.

Living with them · 17 of 19

Which windows actually reduce noise?

Secondary glazing reduces noise more than replacement double or triple glazing, because what blocks sound is a wide air gap and a secondary pane sits 100mm or more behind the original rather than the 16mm or 20mm inside a sealed unit. If you are replacing the window anyway, the specification that matters is asymmetric acoustic laminated glass, not triple glazing.

This is the one place where the more expensive, more modern product is usually the wrong answer, and almost nobody selling windows will tell you so.

Why triple glazing is not the answer

Sound and heat do not behave the same way, so the specification that solves one does not necessarily solve the other.

Heat loss is reduced by adding cavities, which is what triple glazing does. Sound is reduced by mass, by distance, and by breaking up the resonance between panes. Triple glazing adds a third pane but makes each cavity narrower to fit it into the same frame, and the three panes are often the same thickness as each other, which lets them resonate together at the same frequencies. For traffic noise, a well-specified double-glazed unit usually outperforms a standard triple-glazed one.

Triple glazing is a good answer to a cold room. It is not the answer to a noisy road, and it is frequently sold as though it were both.

What actually works, in order

Secondary glazing. A separate pane in its own frame, mounted inside the existing window with a gap of 100mm or more. The wide gap is why it wins, and it is also the only option that works on a window you are not allowed to replace. See secondary glazing.
Acoustic laminated glass, asymmetric. One thick pane and one thin one, with an acoustic interlayer in the laminated leaf. The different thicknesses stop the two panes resonating together, and the interlayer damps what gets through. This is the specification to put in writing when you are replacing anyway.
A wider cavity. Within the same unit, a wider gap helps, which is why a 20mm unit beats a 16mm one for sound while being slightly worse for heat. The two goals genuinely pull against each other here.
Sealing the gaps. Noise comes through holes. A trickle vent, a worn gasket and an unsealed frame perimeter will all undo an expensive glass specification, so the draught work comes first.

Being realistic about the result

Nobody can make a window soundproof, and a quote that implies otherwise is worth treating carefully. What good acoustic glazing does is take the edge off, shift the character of the noise, and move it from intrusive to background.

Two things to be aware of before you spend:

Low frequencies are the hard part. The rumble of lorries and bass from a neighbour pass through almost anything. Glazing deals much better with the higher frequencies -- voices, tyre roar, sirens.
The weakest point sets the result. If the window is excellent and the front door, letterbox or an uninsulated roof is not, you will hear the gap you did not close. Work out where the sound is entering before you specify the glass.

Questions

Will new windows stop my neighbours being noisy?: Only partly, and less than you would like. Speech and television carry a lot of middle and high frequency, which glazing handles reasonably well. Bass and footfall travel through the structure of the building rather than through the air, and no window touches that.
Is secondary glazing ugly?: It is more visible than a replacement window, and that is the honest trade-off. On a period property it is often the only permitted option in any case, and a slim aluminium system mounted to the existing reveal is far less intrusive than the systems people remember from the seventies.
What should I actually write on the enquiry?: Say that noise is the priority, not heat, and ask for a quotation for asymmetric acoustic laminated units with the leaf thicknesses stated. If an installer responds by quoting triple glazing without addressing the question, you have learned something useful about them.

Note This guide is general information about England and Wales, not advice about your specific property. TrustedGlazing is an introducer and does not install, survey or quote. Rely on your installer's survey and your local authority for decisions about your own home.