NOISE REDUCTION BENEFITS OF SECONDARY GLAZING

If we define "Noise" as "a sound that is loud, unpleasant or disturbing", it is easy to think of examples of how this can affect an ordinary household. For example, general traffic on a busy road, loud vehicles such as buses, lorries or motorbikes, car horns or alarms, barking dogs, aircraft or even noisy pedestrians have the ability to ruin a good book, a radio or TV program, interrupt a conversation or in particular, wake a sleeping person. All of these things can lead to stress in varying degrees, and spoil the quiet enjoyment of the home that most people seek.

What can be done to improve noise insulation? Most people start with their windows, because these are the primary source of noise intrusion. The biggest culprits are, ironically, usually in older houses with thicker walls, as these are more likely to have windows with thin, single panes of glass and leaky frames, e.g. typical sash windows. Of course, you can replace or refurbish the windows, but this might not be possible if you are in a listed building, in rented property or on any kind of a budget - more details are on our costed case study page. There are other, more traditional remedies that some people try, such as heavy lined curtains, cork tiles, sound boards in front of the windows, white noise machines, fans or even earplugs(!), but when Secondary Glazing is an option, we would always recommend it as it can be very effective in blocking sound waves, especially when used with Draught Excluders. In addition, it can be inexpensive and quick to fit, there is no disruption or mess around the windows, there is the huge bonus of heat retention and so on. 

For heat insulation, a gap of about 20mm between a secondary panel and the outer windows is recommended. For greater noise insulation, the wider the gap the better, although realistically, the gap size is determined by the structure of the windows and surrounds. Opinions on the subject will vary, especially as much of the information about noise reducing properties of windows comes from manufacturers themselves, but a consensus is that single glazing with a secondary panel is a better insulator than double glazing, and likewise double glazing with a secondary panel beats triple glazing. Whichever you choose, make sure that draught proofing is also used on the outer windows, and that a thermal seal is achieved on the Secondary Glazing.

Easyfix Noise Reduction Experiment

Because Tubeway make and supply Secondary Glazing systems for heat retention, we often get enquiries about the improvment in noise insulation that the same secondary panels will provide. We prepared an experiment, which is filmed in the video on this page, in order to try and illustrate that secondary panels can be an effective way of reducing unwanted and invasive noise in the home. We used a room at our factory where we could park a car directly outside, which meant that the horn, when sounded, was much louder than the background noise, so giving a more realistic reading. It is also a consistent loudness across all three tests. The window itself, although single glazed, is very tight fitting, and this being closed makes the expected large difference. The video then goes on to show how much further reduction is achieved by adding a secondary panel. The readings taken match the perception of being in the room, so we hope this is a useful indication to you, if you are looking at Secondary Glazing to prevent similar noise issues.

For the timing of the car horn being sounded, we had an open phone line so that our colleague in the car could follow the script and react at the correct times.

The noise meter used in the video is a Kewtech KEWSL1 Sound Level meter, but in addition to the readings given the sound track on the video is a good indicator of the general improvement once the Secondary Glazing is installed. We deliberately took readings close to the window to illustrate the change in noise penetration, but it is worth noting that the decibel levels diminish as the meter is moved away from the windows to the other side of the room, and that to the human ear, a 10 decibel reduction is perceived as halving the level of noise.

When we were thinking about filming the video, we looked for straightforward definitions of different sound levels, to give comparisons to any readings we took. The simplest diagram we found is below, which gives fairly straightforward definitions of decibel ranges:

diagram illustrating causes of decibel levels