Toughened or laminated — when the rules require which
Toughened (ESG) glass is heated and then cooled rapidly. When it breaks it shatters into small, blunt pieces. In EN 12600 this is type C.
Laminated (VSG) glass is two panes bonded with PVB film. When it cracks, the glass sticks to the film and stays in the frame, even fully crazed. Type B.
You see toughened glass every day and probably do not even know it: shower cubicles, all-glass office doors, the glass shelf in an oven. Anywhere impact resistance and sudden temperature changes matter.
Laminated glass does the job where someone should not get in, or something should not fall out: shop fronts, balcony balustrades, rooflights. Banks and some private houses fit it as burglary protection, because a thief cannot knock a hole in it with one blow.
In modern construction the two are often combined: laminated glass made from panes that were toughened first. That gives higher impact resistance, and even a broken pane will not fall apart.
Windows and noise from outside
A standard 4/16/4 unit has an Rw of about 34 dB. A 4/18/4/18/4 triple unit is not much better, because three identical panes resonate at the same frequency. An acoustic unit with panes of different thickness, for example 6/16/4/16/6, exceeds 40 dB. With acoustic laminating film you can reach 46–50 dB.
But Rw alone is not enough. A quote should show something like Rw (C; Ctr) = 43 (−2; −5). Ctr is the correction for low-frequency noise: lorries, trams, a train in the distance. Next to a road, Rw plus Ctr is what counts — 38 dB in this example. Two glass units with the same Rw can have different Ctr and behave differently next to a main road.
Why different thicknesses work
Every pane has a coincidence frequency at which it passes sound most easily. For 4 mm glass that is around 3000 Hz. A 6 mm pane has that hole somewhere else, so one covers the other's weakness. Acoustic PVB film damps vibration on top of that.
The unit's Rw is not the window's Rw
The glass is tested in a laboratory as a sample. The window loses a few dB on the frame, gaskets and trickle vent. The manufacturer declares the window's Rw in the declaration of performance — and that is the number to hold on to. Good uPVC profiles with the right unit reach class 6, i.e. about 50 dB.
And finally: the best glass will not help with bad installation. A gap between frame and wall filled with foam alone lets noise through like an open vent.
What to write in your enquiry
Tell us what is outside the window: a busy road, a railway, an airport — or silence, and you just want safety glass in the terrace doors. We will select the unit and quote Rw with the corrections for that exact configuration. Start with the configurator or send us your window schedule.