How Much Noise Does Double Glazing Reduce?

One of double glazing’s many benefits is its ability to insulate the home from a variety of environmental factors. These include heat, intruders and sound. The two panes of glass, plus the thermally insulating gas, provide exceptional thermal performance across the home, increasing the home’s energy efficiency and reducing carbon output and heating costs.

The audible performance of the home also drastically increases, keeping noise out of the home and ensuring that your space is more private. There are few things more embarrassing than an annoying phone call or knock on the door from a disgruntled neighbour over the noise from social gatherings.

The question often comes up of just how effective double glazing actually is at reducing noise. Double glazing installers will almost always provide the U-values (the measure for thermal efficiency) for the performance of their particular installations. Still, they will rarely provide a metric for comparison on noise reduction. Noise is measured in decibels (dB), and we rarely see these as strongly advertised as we do the U-value.

So, just how good are double glazed windows at reducing noise disturbances from the outside world? Here at Double Glazing on the Web, we intend to find out.

how does double glazing reduce noise

How do double glazed windows work?

Before we get into measurements and comparisons, it is probably a good idea to establish just how double glazed windows perform the job they’re designed to do.

Double glazed windows feature two panes of glass on either side of an air pocket. This air pocket is more accurately described as a vacuum that is filled with a thermally insulating gas, typically argon. The gas provides the window with its thermally insulating capabilities, as the gas does not conduct the heat well.

In terms of how the window performs with noise reduction, the three key elements are the glass, the size of the gap and the quality of the frame. The glass itself helps with stopping noise pass through because of how dense materials like glass absorb vibrations in the air. Similarly, the gap between the two panes forces the vibrations in the air to pass through a significant space. The larger the gap, the greater the noise reduction. Finally, the quality of the frame will bring the window’s performance together. You could have the largest gap possible with good quality glass, but if they’re not fitted properly in the right frame, you’re going to struggle to get the performance that the individual elements suggest.

How to measure noise reduction

Sound, as mentioned, is measured in decibels. The higher the dB value, the louder the noise and the more noticeable it is. The decibel is actually measuring the force of the sound, in other words, how violently it is vibrating the air around the measuring instrument. The higher the force of the sound, the more vibrations there are and the louder it is.

Humans can hear sounds between 0 and 140 decibels, although it would be difficult to measure the difference between one or two-decibel measurements without keen training. Anything under 30 dB is considered to be extremely quiet. Breathing, for example, is considered to be around 10dB. We tend to speak (with our indoor voices) at around 60dB. Helicopters and police sirens come in at around 100 dB to 110 dB, with fireworks and jet engines coming in well over 120-130 dB. Anything higher than that is a great risk to our ears.

In windows, we measure sound reduction with the RW rating, referring to the weighted sound reduction index. When purchasing new windows, you can ask to see the Rw rating, which measures the level of sound insulation in the product – the higher the rating, the better the sound insulation.

How effective is double glazing at reducing noise?

As sound travels through a double glazing installation, the glass and insulating gas dampen the vibrations and reduce the transmission of the sound. Double glazing reduces sound by around 20-65%, depending on the quality. This translates to around 35 decibels, which is quite significant. It reduces a conversation just outside the window to barely a whisper, and sound that has to travel further is going to struggle to get through the installation.

Properly installed double glazing with good frames and a quality build can bring this value even higher, up to around 40 dB, but you would struggle to get much higher than that with double glazing.

What about triple glazing?

For those reading this article and thinking that’s just enough for me, you may want to consider triple glazing. Triple glazing works on the same level as double glazing, except you have three panes of glass and two air pockets instead of two and one, respectively.

With the extra layers of protection, you’re looking at even further noise reduction. Companies selling triple glazing are claiming levels as high as 54 dB, which would turn a conversation just outside the window quieter than someone breathing in the same room, which is pretty remarkable.

Unfortunately, triple glazing does come with exceptionally high costs, and it is yet to take the market by storm to become the norm over double glazing. Still, it may be something worth considering for the future if it is out of your budget currently.


Double glazing reduces noise significantly in the home. 35 dB is nothing to shake a stick at and will greatly increase the privacy and tranquillity of your living spaces. Triple glazing is the next step up for those looking for that little bit extra. However, this comes with a dramatic increase in cost compared to double glazing as it is not standard quite yet across the UK.

Here at Double Glazing on the Web, we share our expertise with the public to feel confident when dealing with installers and understand, with greater clarity, just what it is they are purchasing for their home.

If you’re feeling inspired, please use our quick and easy online pricing tool to get an accurate price from across the industry. We do all of the research for you and make sure that we only provide you with the absolute best prices and the best service so you can make an informed decision about your next project. You can also contact us through our online contact form if you have any specific questions!

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