Does triple glazing reduce noise?

Quiet bedroom at dusk with a closed white window overlooking a busy main road

Triple glazing reduces noise a little more than double glazing, about 3 dB for the third pane, sometimes less. The bigger gains come from laminated acoustic glass, panes of different thickness and an airtight frame, which can take a unit from about 29 dB (Rw) to 34 dB and above.

How sound gets through a window

Sound travels through the glass, around the frame seals and through vents. A window is only as quiet as its weakest path. That is why airtight fitting and acoustic trickle vents matter as much as the glass.

The glass that makes a difference

Laminated acoustic glass: a plastic interlayer damps vibration. The single biggest upgrade.
Different pane thicknesses: stop the panes resonating at the same frequency.
Wider cavities: help with lower frequencies.

What the numbers mean

A standard 4/16/4 double unit is about Rw 29 dB; standard laminated units about Rw 33, and units with an acoustic interlayer the mid to high 30s. A 3 dB improvement is noticeable; 10 dB sounds roughly half as loud. Claims of an extra 10 dB from a third pane alone are not backed by published data.

Which rooms to upgrade

Most people put acoustic glass in the rooms facing the noise, usually front bedrooms, and standard triple glazing elsewhere.

Questions

Is triple glazing quieter than double?

Slightly. For real noise reduction, add a laminated acoustic pane.

What is Rw?

A single-number rating of sound reduction in decibels; higher is quieter.

Sources

Pressglass: sound insulation of glazed units

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