Does Secondary Glazing Work?


Whether you’re investing in new loft insulation or a state-of-the-art alarm system, one of your first questions will always be “does it work?”. Secondary glazing is no different.

But while loft insulation has a simple yes or no with its insulative qualities and alarms have yes or no with their security benefits, secondary glazing has a number of functions for which you can ask “does it work?”.

In this post, we’ll discuss the range of benefits on offer with secondary glazing – and whether it works.

Does secondary glazing work for thermal insulation?

One of the main reasons homeowners install secondary glazing is to improve thermal insulation. Windows are a key part of your property’s thermal envelope – along with the door, floor, walls and roof – which separate your home from the weather outside.

Whether it’s because of poor glazing, small gaps or just wear and tear, single-glazed and even double-glazed windows can let in too much cold air. The opposite applies in summer, when they let the cool air out of your home and cause things to get uncomfortably warm.

By adding an additional barrier between your home and the outside elements, secondary glazing works to improve thermal insulation in your home. That includes a gap of air between the window, acting as an effective insulative layer.

By using Pilkington K or Low E glazing, a window’s thermal efficiency can increase by as much as 60-70% with secondary glazing installed. Put simply, secondary glazing works for thermal insulation. That means a warmer home in winter, and a cooler one in summer.

What about noise reduction?

It’s not just the cold you want to keep out. Sometimes, the outside noise can be just as bad – if not worse than the weather at disrupting your day-to-day life. Traffic, noisy neighbours or even aeroplanes flying above can create unbearable noise in your home – and windows are a key point of entry for this noise.

Can secondary glazing help with noise reduction? It certainly did for Heathrow’s closest neighbour, who installed secondary glazing to block out the noise at his home just 300 yards from the Europe’s busiest airport.

Rather than being blocked out entirely like rain or cold air, sound waves dissipate as they pass through the air. Secondary glazing works to enhance this dissipation by creating a non-uniform barrier, unlike the structure of double- or even triple-glazed windows.

With the right specification of glass thickness and distance from the existing window, secondary glazing can reduce sound levels by more than 50 decibels – five times the effect of double glazing – which effectively halves the noise getting into your home.

Does secondary glazing work for condensation?

It’s a resounding yes. Condensation forms on cold surfaces, which draw the moisture out of warm, humid air. This can occur on your windows in two ways.

Most commonly, single glazed windows will become cold on the inside because there’s only a single pane of glass separating them from the outside. However, double glazed windows can also become cold on the inside as their sealing breaks down. In both cases, condensation forms across the inside of your windows, which can create an unappealing misty appearance and even roll down to create pools of water on the windowsill.

Condensation can also form in the gap between panes on double- or triple-glazed windows. If the sealing breaks down, moisture will seep into the gap and condense on the glass between the inside and outside of your home. Frustratingly, you won’t even be able to wipe away this condensation.

By creating an effective internal seal, secondary glazing allows for balanced ventilation between the existing window and secondary glazing unit, while preventing it from becoming too cold. In turn, that eliminates or significantly reduces condensation on single- or double-glazed windows.

It even works for security

Windows are one of the most common points of entry for burglars. Why? They’re usually the most fragile. If a burglar can’t find any unlocked doors, they’ll move onto the windows, which can often be broken all too easily.

Single glazing is usually so weak it can be smashed accidentally. If a child’s football can break it, it’s not going to stand up to a determined thief. While double glazing is slightly better, it can still be broken through with a couple of hard strikes.

Secondary glazing adds an extra layer of security to your windows, which is much harder to get through from the outside. Even better, it can be fitted with locks, handles and toughened or laminated glass to further enhance the protection on offer.

Does secondary glazing work to retain character?

Replacement isn’t a practical option for windows on heritage properties. An unauthentic replacement will disrupt the style and character of the building and reduce its value. If the building is listed, its windows will even be protected by law – with the same reasons in mind.

But that doesn’t mean you have to put up with a cold, noisy and insecure home. Secondary glazing is a discreet way of improving your heritage windows’ efficiency and performance across the board. With a slim additional panel installed on the window’s interior recess, there is no loss of historic fabric and minimal impact on its appearance.

The proof that secondary glazing works? Clearview are suppliers to the National Trust, and secondary glazing has been recommended by Historic England:

“Secondary glazing when carefully designed and installed allows the original windows to be retained unaltered, and where necessary repaired, whilst reducing air leakage and conducted heat losses. As a result there is no loss of historic fabric and in most cases the installation is easily reversible.”

Put secondary glazing to the test

The verdict is in. Secondary glazing does work. It’s time to try it for yourself. With Clearview, you can choose between professional secondary glazing or our fully assembled DIY Secondary Glazing kits. Our DIY kits are pre-drilled and installation ready, with a measuring guide and clear instructions. So, whichever option you choose, you can expect a quick, hassle-free installation.

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Clearview secondary glazing - the solution to significantly improved acoustic and heat insulation to your property, making your home or offices more comfortable, secure, greener and cost efficient to run. Achieved without the disruption of replacement windows, and without damaging the character of your building.

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