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Best Windows for Noise Insulation

Noise pollution is a growing concern for homeowners across the UK.  If you live in an especially noisy area, such as the vicinity of a busy road, airport or nightclub, then you’ll want to keep the clamour of the outside world at bay.  By the same token, if you’re fond of blasting loud music or shouting at the television at the top of your lungs, then you might want to offer the outside world the same protection.

When it comes to sound insulation, much as with heat insulation, windows represent a weak point in any building.  Glass, after all, vibrates more easily than brickwork.  Fortunately, it’s a weak point we can address by upgrading to a more modern window.  Let’s take a look at some of the available options, and consider how they might help protect you from outside noise.

How is sound absorbed?

Before we can establish how best to stop sound, it’s vital we understand what sound actually is.  When we hear anything, whether it’s Rachmaninoff’s second piano concerto, or the barking of a neighbour’s Alsatian, we’re perceiving tiny changes in air-pressure around our ears.  These vibrations can be measured in two different ways – their amplitude, which is most commonly measured in A-weighted decibels (or dBA), and their frequency, which is measured in hertz (the number of vibrations occurring per second).

Sounds waves are extremely difficult to destroy altogether.  They don’t just vanish when they encounter an obstacle; they’re forever bouncing around, reverberating, and changing shape as they do so.  When sound impacts the glass of your window, it’s effectively split into three: a certain portion echoes back in the opposite direction (which we might call an echo), another portion is absorbed into the material, and a third passes through to the other side.  In order to produce the most effective noise-reducing glass, our aim should be to keep this final quantity as low as possible.

sound waves

The human ear is better at perceiving some frequencies than others (most often those in the range of human speech).  Moreover, certain mediums will be better at transmitting certain frequencies than others – which is why the top end of the audio spectrum might seem muffled when your head is underwater, or the source of the sound is in another room.  Once you open a door, however, things will immediately sound much crisper.

Provided we’re not talking about extreme noises, like that of a gunshot or a bomb going off, we can think of sound waves passing through air as akin to a weight on the end of a spring. When the weight is moving very quickly up and down, the damping force of the spring will be high, causing it to slow more quickly.  When the weight is moving more slowly, the spring will act upon it less – even if the speed of the weight is the same.

What this means is that higher frequencies will naturally encounter more resistance than lower ones – which is why you won’t be able to hear a cymbal through a wall, but you might be able to hear a bass drum.  This consideration is vital when we’re thinking about how to protect our homes from outside noise – as certain sorts of noise will be more easily dealt with.  If you’re irritated by the yapping of next door’s dog, or of a baby who won’t stop crying, then a suitably sound-resistant window might be just what’s required; if you’re worried about your neighbour’s Lamborghini roaring, or of house music being playing at a neighbouring nightclub, then your choice of window alone might not be enough to make the difference.

How effective is double glazing at reducing noise?

Double glazing is among the most popular options for combatting both noise and heat transference.  So much so, in fact, that your property is likely to already have it equipped.  The technology works by sandwiching a layer of vacuum, inert gas, or dehydrated air, between two layers of glass.  This makes it difficult for sound waves and heat to get from one side to the other, as each successive layer of glass will be able to absorb a given portion of the wave.  This effect is made all the more pronounced when we introduce a third sheet of glass.

That said, while multiple sheets of glazing might confer some benefit, the most considerable improvements in noise-dampening are to be achieved through thicker sheets of glass, and larger areas of empty space.  These improvements will also result in better heat efficiency, too.  Of course, thicker glass will require a sturdier surrounding frame – which is why weaker plastic windows and doors are at a comparative disadvantage to stronger wooden and aluminium frames.

What other steps can I take?

If you’d like to reduce the amount of noise that’s leaking through your windows, you’ll be pleased to learn that there are a few other steps you can take to address the problem.   These include hanging heavy, thick curtains, which will act as a barrier to soundwaves and help absorb the sound waves reflecting around your room.

If you’re the owner of a property that’s listed or in a conservation area, you might find it difficult to obtain planning permission for double-glazing.  In this instance, you might consider secondary glazing instead.  This works by placing a second sheet of glass directly behind your existing window to help improve both noise and heat insulation.

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timber window

Is Triple Glazing Worth It?

Windows are a notorious point of thermal weakness in any building, and it’s essential that they’re made as heat-resistant as possible. Double glazing is a popular means of doing this; it sees two panes of glass placed in parallel with one another, with the space in between occupied by a vacuum, or an inert gas like argon.

But if double glazing yields such dramatic improvements in thermal efficiency, then why should we not also consider adding more panels of glass? Wouldn’t that improve heat-retention even further? Let’s get the facts on triple glazing.

What is triple glazing and how does it work?

Triple glazing is made up of three individual panes of glass secured in a sealed frame (unlike double glazing, which is formed of two panes of glass, or single glazing, which features just one).

As with double glazing, each pane of glass is spaced slightly apart and the cavities are filled – usually with an inert gas such as argon, xenon, or krypton.

The type and thickness of the glass, alongside the width of the cavities, the gas used to fill them, and the fact that there are three panes of glass instead of just one or two, combine to create a window with far superior insulation properties compared to single or double glazing.

triple glazed window

How thick is triple glazing?

A typical triple glazed window will be formed of three 4mm panes of glass separated by two 16mm filled cavities – 44mm in total.

By comparison a standard double glazing unit is 28mm thick. While there is a significant difference in the thickness of double and triple glazed units, most walls can still comfortably accommodate triple glazed windows.

How effective is triple glazing?

The performance of windows is rated with a U-value. This is the rate at which heat can transfer through a material – so the lower the number, the better.

Again, windows and their performance vary, however as a general rule quality double glazing will have a u-value of 1.4W/m² or even 1.2W/m². The typical u-value of a triple glazed window is 0.8W/m².

What’s holding triple glazing back?

Since double glazing has been around for decades, and we haven’t all moved on to triple glazing, you might imagine that the technology isn’t quite perfect. And in most situations, this is so. There are several reasons for this:

The cost of triple glazed windows

Triple glazed windows are considerably more difficult to manufacture than double glazed ones. Since demand (in the UK at least) is so low, triple glazing is considerably more costly than double glazing.

Triple glazed windows reduce light transmission

As well as preventing heat from escaping your property, triple glazing will also impact the amount of sunlight that can get in. The result is a markedly dingier look to the room, which might be precisely the opposite of what you’re looking to achieve. By the same token, this lack of sunlight will reduce the extent to which your home is heated by sunlight in the daytime – which, during summer, can actually increase your energy expenditure.

Triple glazing has minimal impact on noise penetration (compared to double glazing)

Sound travels more easily through a solid piece of glass than it does through the air – just place your ear against your window and tap it if you’d like an illustration of this. Consequently, triple glazing – while it might offer passable protection against noise – will not perform as well as double glazing where the gap is the same size.

What’s better? Double or triple glazing?

It’s clear that triple glazing is, all other things being equal, superior to double glazing. In areas of the world where sunlight is limited, and winter temperatures are especially frosty, this is particularly so. That’s why Scandinavian governments go to great lengths to subsidise triple glazing installations.

The reason that double glazing has been around for so long without eventually morphing into triple or quadruple glazing is that successive improvements have seen an evolution in the technology – one which eliminates the need for a revolution. Specifically:

• The gaps between the panels have increased, improving soundproofing.
• The manufacturing process has been refined, slashing costs.
• The gap between panels has been filled with exotic inert gases, which yield superior performance.

All of these improvements mean that the double glazed windows of today far outperform those of decades gone by. With this in mind, there’s little reason (excepting in the circumstances we’ve touched upon) for homeowners to choose anything else.

If you find that you’re unable to stretch to installing triple glazing, then be sure that you’ve explored more low-tech alternatives. Drawing heavy curtains in front of double glazed windows at night-time, for example, can provide considerable protection against heat loss.

For more information, read our article “Double Glazing vs. Triple Glazing“. Alternatively, shop for triple glazed windows here.

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