Secondary Glazing

Secondary Glazing

Improve energy & acoustic performance
without compromising on style or authenticity

What is Secondary Glazing?

Where double glazing and even triple glazing are common terms that most people are aware of and know that they improve energy efficiency, Secondary glazing is a far less understood. Secondary glazing is a fully independent internal window, fitted on the room side of an existing primary window. This provides significant noise reduction, improved thermal performance and enhanced security and usually constructed from a lightweight aluminium frame. There are many styles including vertical and horizontally sliding, side hinged opening and fixed.

What Is It Used For?

The main use of secondary glazing is to reduce the amount of noise pollution entering your home. If you are troubled by noisy roads, low flying planes or perhaps a nearby school playground then you could benefit from installing secondary glazing. When properly installed, secondary glazing can reduce noise intrusion by up to 50db and to make that real, a reduction in 50db can take you from an ear-splitting noise to a calm, comfortable background babble.

Can Secondary Glazing be installed in my listed building?

If your home is listed, in a conservation area or has protected status then secondary glazing is the preferred method of upgrading your home’s energy efficiency and sound insulation. It is advised that before undertaking any work you contact your local conservation officer as every year we have to reinstate timber sash windows after the homeowner has replaced them with uPVC options without informing the local officer and has subsequently been told to skip them at their expense! So always check what is and is not allowed before starting any renovation. We have a vast wealth of experience and can help you get permission for works and navigate the process. You can read our do’s and don’ts of listed building restoration here.

Does Adding Secondary Glazing Improve Energy Efficiency?

Yes! Along with sound insulation, secondary glazing for sash windows also drastically reduces heat loss. While not as effective as double glazing because the gap between the two panes is filled with air rather than a noble gas it can still reduce heat loss by up to 65%.

Does It Offer Any Added Security Benefits?

Original single glazed sash windows with there thin glass do not offer much impediment to forced entry of your home. Installing a strong, aluminium framed second pane of modern, toughened glass adds an extra layer of defence against intruders. Our units can also be locked.

Will it look ugly?

We use a thin, discreet frame which can be coloured to match your walls or existing timber window. Once installed the secondary glazing will blend into the background and not obstruct your view out or sunlight coming in through your window.

Our bespoke products support the sympathetic treatment of most window styles. They come in two ranges: Traditional and Heritage.

Traditional Range

With its slim, discreet aluminium profile, our traditional range offers minimal sight lines and easy access to the primary glazing, making it a popular choice with homeowners.

Heritage Range

Heritage products utilise a slightly thicker, heavy-duty aluminium profile suitable for large-scale commercial installation, as well as smaller applications.

As with our traditional range, all heritage products offer a high level of additional security, easy access to the primary glazing and secure night ventilation position.

Secondary Glazing Horizontal Sliding Window
Secondary Glazing Vertical Sliding Window
Secondary Glazing Insert Panel
Secondary Glazing Lift Out Window
Secondary Glazing Traditional Hinged Casement
Secondary Glazing Hinged Casement Window
Secondary Glazing Optional Extras

Bring the noise!

Well-fitted secondary glazing provides outstanding noise reduction — outperforming double glazing.
Chiltern Dynamics, market leaders in acoustic testing and modelling, found our windows capable
of reducing noise levels by over 50dB — enough to quieten the busiest railway line or rumbling road.

Thanks to its unique soundproofing capabilities, secondary glazing can reduce the noise pollution caused by various sources. For many homeowners, traffic noise is their biggest concern. In these instances, secondary glazing with thicker glass and fitted correctly can make the world of difference.

Our acoustic glass provides maximum sound insulation, which can be further enhanced with a 150-200mm air gap between secondary glazing and your existing primary windows.

This massive impact is not lost on many of our grateful customers, as we help them to better relax,
concentrate and improve their quality of life.

Screaming Noisy Child
Eliminate draughts and can reduce heat loss by up to 65%

Feel the benefit

Warmth is a valuable commodity and by creating a second barrier to the elements, it is an ideal way to
reduce wasteful thermal heat loss. In fact, there are few better ways.

The creation of an insulating layer of air is as important to the retention of energy as the fitment and seals. With the right glass, the result can be a reduction in heat loss by as much as 65%.

For thermal insulation, low-E glass is often the best choice because the glazing has been designed and engineered to provide:

  • the very best single glazing insulation
  • maximum energy conservation
  • an extremely discreet installation
  • an environmentally friendly solution
  • an affordable investment with quick returns

The resulting installations can exceed Building Regulations’ requirements, offering significant cost savings in the process. It is also the product of choice for traditional buildings and properties; listed buildings and conservation areas, thus maintaining their appearance, character, integrity and value.

Peace of Mind

Windows are often seen as a weak point in building security. Secondary glazing offers an affordable, discreet and highly effective solution to help counter this problem.

For homes, the benefits are clear. Unlike single windows, secondary glazing is extremely difficult to open from the outside and provides an additional physical barrier against forced entry.

Should attempts be made to breach the secondary glazing, the outer glazing can act as a vibration-sensitive alarm, thus offering a warning before an attempt to break into the secondary glazing is made.

Frames are made from tough aluminium and securely fixed to resist forcing. The use of cutting tools are deterred through a sophisticated combination of glass, resin and polycarbonate, whilst the risk from the tampering of locks and catches, or removal of the glass or glazed panels, is also negated.

Man relaxing on sofa

Types of Secondary Glazing for Sash Windows

The key to selecting secondary glazing is to choose a product that suits the property owner’s need but has the lowest visual impact when installed into a traditional timber window. There are four main types of secondary glazing:

Lift Out Units

These units are used where the primary window is fixed or where a customer seldom requires access to open the window for ventilation.

Hinged Units

These units are generally used with casement/hinged primary windows.

Vertical Sliders

These units are normally used on vertical sliding sashes with the meeting rails aligning with the primary window meeting rail.

Horizontal Sliders

Normally used in conjunction with either sash or casement windows where full access is required and where there is sufficient space internally to open the casement secondary glazing.

Plenty of Choice

With a range of styles, colours, glazing options and materials to choose from, you can find the perfect match for you and your home.


To achieve a higher acoustic performance a minimum gap of 100mm should be achieved between the primary window glazing and the secondary glazing. The optimum desirable gap is 150mm. The installation method will depend upon the depth of the primary window reveal. If the reveal is insufficient to achieve the minimum 100mm gap then the window will require boxing out to the required depth. Our Surveyors will advise on this and any other issues at the time of the survey.


We offer a wide range of product designs requiring careful installation and specification knowledge, and we know that the perfect fitting of your new windows and respect for your property are amongst the very highest priorities.

Our attention to detail extends to the company we keep and we work with the best installation teams. We offer daytime appointments at a time to suit you, so you can decide which secondary glazing products work best without feeling rushed or pressured.

Our aim is to provide the best possible product, together with excellent service. To that end, we’ve been focussed on delivering great quality, value and service to our customers for many years.

We can provide a comprehensive range of unobtrusive styles to suit most window and property types. And whether it’s for the added security, noise reduction or energy efficiency, our windows provide years of robust, trouble-free service.

To learn more, please get in touch.

No Draughts or Rattles

We recommend having your primary (original) window inspected, and possibly renovated, too. To make sure the window is in good health when fitting the secondary glazing unit. Visit our ‘contact us’ now page and let us help make your windows exceptional.