Noise Reduction with Secondary Glazing
Noise is one of main reasons most people start looking at secondary glazing. It might be traffic outside a bedroom, aircraft overhead, late-night activity nearby or simply the everyday noise of a busy street.
Secondary glazing can make a substantial difference because it adds a second, separate barrier behind the existing window. With the right cavity, glass specification and seals, the combination can achieve very high levels of sound insulation.
The important point, however, is that there isn’t one noise-reduction figure that applies to every window. Acoustic performance depends on the complete installation.
Understanding decibels
Decibels can be difficult to picture because they don’t work on a simple, straight scale.
A 10dB reduction, for example, is generally perceived as roughly halving the loudness of a sound. So even what looks like a relatively small change in the number can make a noticeable difference in a room.
With secondary glazing, noise reduction can be significant. Our systems can reduce noise by up to 45dB, depending on the window, the installation and the type of noise involved.
The important words there are “up to”. 45dB is not a guaranteed result for every home. The final performance depends on factors such as the existing window, the gap between the two windows, the glass used and how well the system is sealed.
In practice, the result will vary from property to property, but even a smaller reduction can make outside noise feel far less intrusive.
What affects how well secondary glazing reduces noise?
Several things influence how much of a difference secondary glazing can make.
The gap between the windows
The distance between the original window and the secondary glazing is one of the biggest factors.
A wider gap generally improves acoustic performance because it creates greater separation between the two panes of glass. This is one of the reasons secondary glazing can be so effective compared with a standard sealed double-glazed unit, where the gap between the panes is much smaller.
Where space allows, a larger cavity can be particularly useful when noise reduction is the main priority.
The glass
The type and thickness of glass also matter.
Using different glass thicknesses can help because the two panes respond differently to sound. Laminated acoustic glass can also improve performance against certain types of noise.
That said, glass is only one part of the overall system. A well-designed cavity and good seals are just as important.
The seals
Sound can travel through very small gaps, so the secondary glazing needs to fit and seal properly.
A tightly sealed unit will perform better than one with gaps around the frame or opening sections. This is why installation quality matters so much when noise reduction is the goal.
The condition of the existing window
Secondary glazing works alongside the original window, so the condition of that window also has an effect.
If the primary window is loose, rattling or has obvious gaps around it, some sound will already be getting through before it reaches the secondary glazing.
Improving the fit and condition of the original window can therefore help the whole system perform better.
Does secondary glazing work equally well for all types of noise?
Not quite.
Some sounds are easier to reduce than others. Everyday street noise, voices and general background noise can often be reduced very effectively.
Lower-frequency sounds, such as heavy traffic rumble, aircraft noise or bass from music, can be more difficult to deal with. These sounds have longer wavelengths and can travel through different parts of a building more easily.
Secondary glazing can still make a considerable difference, particularly because of the larger gap it creates between the two panes, but very low-frequency noise may still remain noticeable.
It is also worth remembering that windows are not always the only route noise takes into a room. Sound can also travel through walls, roofs, floors, vents, chimneys and other openings.
In many older properties, however, the windows are one of the weakest points, so improving them can make a very noticeable difference.
Is secondary glazing better than a replacement window for noise?
In many situations, it can be.
Standard double glazing usually has a relatively small gap between the two panes because it is designed primarily with thermal performance in mind.
Secondary glazing works differently. The additional pane sits much further away from the original window, creating two separate barriers with a much larger gap between them.
That greater separation can provide a real acoustic advantage.
This does not mean that modern double or triple glazing cannot perform well against noise. Specialist glazing, different pane thicknesses and acoustic laminated glass can all improve performance.
But where the original window is being retained, secondary glazing can be a particularly effective way of reducing outside noise without replacing the existing windows.
What secondary glazing won’t do
Secondary glazing cannot make a room completely silent.
You may still hear very loud events, particularly low-frequency noise, and some sound may enter through other parts of the building.
What it can do is reduce the amount of noise coming through the window so that it becomes less intrusive and easier to live with.
For homes affected by traffic, aircraft, nearby businesses or general street noise, that can make a significant difference to everyday comfort.
Working out what your windows need
The right secondary glazing specification depends on the type of noise you’re dealing with, the space available between the primary and secondary windows, and the condition of the existing windows.
Those are things that are best assessed at the property rather than worked out from a brochure.
As a manufacturer, Incarnation fabricates your secondary glazing to order. The actual survey, quote, installation, and guarantee are handled entirely by your chosen independent window installer. They’ll assess your windows and the space available, recommend the most appropriate configuration and glass, and provide us with the precise measurements we need to manufacture your system.
If you don’t already have an installer, we can help you find one in your area.
