Traffic, trains, nightlife, aircraft and busy neighbours can all make a room hard to sleep, work or relax in. Acoustic secondary glazing is one of the most effective ways to reduce outside noise coming through windows, and you don’t need to replace the windows you already have. This page explains how noise reduction secondary glazing works, what makes the biggest difference, and how to choose the right specification.
Why secondary glazing is good at reducing noise
Sound passes through a window as vibration. A single pane, or a sealed double glazed unit with a narrow gap, vibrates as one system and passes a lot of that energy into the room. Secondary glazing adds a second, independent window on the room side, separated from the original by a much wider air gap. The two panes are decoupled, so less vibration is passed from one to the other, and less noise reaches the room.
Historic England’s guidance on traditional windows notes that secondary glazing is even better than double glazing at reducing noise. That is why it is so widely used in city-centre homes, offices and hotels.
What makes the biggest difference to sound insulation?
The air gap
In general, the wider the gap between the original window and the secondary glazing, the better the sound insulation, particularly at lower frequencies. Where the window reveal allows, positioning the secondary unit to give a generous cavity is one of the most effective things you can do.
Glass thickness and type
Heavier glass resists sound better, and using a different thickness of glass from the original window helps avoid both panes resonating at the same frequency. Acoustic laminated glass has a special interlayer bonded between two sheets of glass that damps vibration and is particularly effective against higher-pitched noise. Our aluminium range offers 6.8mm, 8.8mm and 10.8mm acoustic laminated glass, as well as standard toughened and laminated options.
Airtight seals
Noise follows air. Even small gaps around a window can let a surprising amount of sound through, so a well-fitted secondary unit with good seals, and an opening system that closes tightly, matters as much as the glass. Accurate measuring and careful fitting are essential.
The type of noise
High-pitched sounds such as voices, sirens and birdsong are generally easier to reduce than low, rumbling noise from heavy traffic, buses or bass-heavy music. The latter benefits most from a larger air gap and heavier glass.
Acoustic secondary glazing vs acoustic double glazing
Acoustic double glazing replaces the whole window, and the gap inside a sealed unit is narrow. Secondary glazing keeps your existing window and adds a second one with a much wider cavity, which is why it often performs better against noise. It also avoids removing original frames, which matters for period and listed buildings. You can use secondary glazing behind existing double glazing too, provided there is enough depth in the reveal.
Choosing the right opening style for a noisy room
- Fixed secondary glazing has no opening joints, so it is simple to seal. It suits windows that never need to open.
- Horizontal sliding and vertical sliding units let you open the window for ventilation and cleaning. Vertical sliders suit sash windows.
- Hinged / casement units give full access to the window behind.
- Lift-out panels suit windows you rarely need to open.
Remember that rooms still need ventilation, and any window needed as a means of escape must remain openable.
Acoustic secondary glazing for hotels and commercial buildings
Noise is one of the most common complaints in city-centre hotel rooms, apartments and offices. Our clients include hotels such as The Midland in Manchester (Leonardo Hotels), Holiday Inn (IHG), Kimpton Clocktower and Whitworth Locke, as well as Burnley FC. For commercial projects, request a quote with your window schedule and we will advise on suitable glass and opening types.
How much does acoustic secondary glazing cost?
Acoustic laminated glass costs more than standard toughened glass, and thicker specifications cost more again. Size and opening style also affect the price. Choose your style, enter your sizes and select an acoustic glass option for an instant guide price including VAT. See our secondary glazing cost guide for more detail.