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What is Secondary Glazing?

Secondary glazing is a fully independent, window system installed in front of the internal face of existing windows. The original windows remain in position and in their unaltered form.

It is a totally reversible installation, used mainly in listed properties, which need to retain the original period single-glazed windows. The main reason for installation is to alleviate issues due to heat loss and acoustic insulation and where window replacement is not an option due to local authority planning permissions and consents.

Secondary glazing solutions are available in fixed, removable and openable units.

  • Openable options can be either side hung casements or horizontal or vertical sliding sashes. These allow access to the external window for cleaning, maintenance and ventilation.
  • Fixed forms of secondary glazing are designed to be removed in warmer months, when the thermal benefits are not required, or for occasional cleaning and maintenance.
  • Removable units are a cost effective solution, which can be removed more readily than the fixed option via sashes that lift out, leaving the perimeter frame in situ.

Secondary glazing is suitable for a wide range of both commercial and residential applications: Listed buildings, conservation areas, offices, schools, colleges, universities, hospitals and hotels.

Benefits of Secondary Glazing

The benefits of secondary glazing include:

Improved thermal insulation – With increased energy costs, emerging environmentally focused initiatives such as BREEAM and continuous revisions to Building Regulations, the drive to create thermally efficient buildings is higher than ever. The installation of secondary glazing provides an additional layer of insulation, increasing thermal efficiency, reducing heat loss by up to 65% and ultimately reducing energy costs.

Increased acoustic insulation – Particularly relevant to residential buildings, where noise pollution from traffic and other noise sources can create an issue for occupants (leading to the introduction of Building Regulations Approved Document E), the need to control noise in our living spaces is essential. Secondary glazing out performs, double and even triple glazing, boasting a sound reduction performance of up to 80%, providing an effective solution for a range of commercial and residential properties.

Enhanced security – Particularly effective in listed and period properties, where the original windows may lack modern security fittings, secondary glazing provides a secure additional barrier.

Secondary glazing can be supplied with all types of glass to suit the application. For example, low emissivity glass to help with thermal retention, laminated glass which resists breakage and also filters out 95% of UV light, which has the additional advantage of protecting soft furnishings from fading, specialist acoustic glass and double glazed units.

Speak to us today if you think secondary glazing is of interest. We are committed to providing you with a responsive and personal customer service.

Horizontal sliders

Horizontal Sliding Secondary Glazing

The horizontal sliders are our most popular option. With their slim appearance and versatility, they can be installed into all property types and scenarios.

From the most modern property right through to listed buildings, the horizontal sliders are discreet, functional and allow full access to the primary windows for cleaning and maintenance.

They are available as two, three and four panel options. With light and heavy duty frame options to suit all sizes of aperture. A cost effective solution to address both noise and thermal issues, along with providing a secure additional barrier to enhancing security.

Vertical Slider

Vertical Sliding Secondary Glazing

The perfect choice to be used in conjunction with sash windows. Most often used in older period properties, where secondary glazing needs to blend in with existing traditional box sash windows. The panel split can be arranged to give suitable access to the primary window, along with mirroring the existing sightlines.

These vertical sliders will enhance both thermal and acoustic insulation and are in keeping with the look of heritage properties.

A discreet application with all the functionality and appearance of the existing sash windows, but with the benefits of enhanced thermal and acoustic insulation, without the need to install double glazing.

Hinged Casement

Hinged Secondary Glazing

Hinged secondary glazing windows are a good choice where regular access to the primary windows will be required. They don’t introduce any sightlines, so will not detract from the look of the existing fenestration.

A versatile option which can be supplied with hinges positioned on the left or right subject to your requirements. They can also be supplied with a tilt & turn operation to allow ventilation, without the sash opening into the room. Other options include double side hung and top hung.

A very popular choice for both residential and commercial applications to enhance both acoustic and thermal insulation. Providing full access to the primary window for cleaning and regular maintenance. The additional glazing layer enhances property security.

Lift Out Windows

Lift Out Secondary Glazing

Lift out secondary glazing is an ideal option for insulating a window where only occasional access for cleaning and maintenance is required.

They are slim, unobtrusive and will insulate the window area. Access to the primary window is via removal of the sash leaving the perimeter frame in situ.

The units can be face or reveal fixed, depending on the situation they are being installed into and also the insulation requirements of the property. Face fix allows the secondary glazing to be installed close to the exiting window. This is recommended for thermal insulation. Reveal fix allows the secondary glazing to be installed away from the existing window, creating a larger cavity between the primary window and secondary glazing. This creates an air gap which dampens sound ingress, enhancing the acoustic insulation properties of the secondary glazing installation.

As with all secondary glazing, the lift out unit offers a solution to noise and thermal issues that may be experienced in certain properties that had to adhere to conservation requirements.

Secondary glazing is a simple and totally reversible installation that does not have an impact on the fabric of the building or the appearance of the property. All the original characteristics of the property remain unaltered.

Fixed Windows

Fixed Secondary Glazing

Fixed secondary glazing is ideal where regular access to the prime window is not required.

They can be removed infrequently to allow access for essential cleaning and maintenance.

The most basic of the secondary glazing range, to enhance thermal and acoustic insulation, completely sealing the window area to improve insulation performance.

These units are often used for some of the more bespoke shapes and designs, especially the larger arched windows such as those in an ecclesiastical setting.

Bespoke Options

Bespoke Secondary Glazing

Historic buildings often present additional challenges. With existing stained glass and leaded lights, bays, arched and even circular windows.

But with our ability to offer truly bespoke secondary glazing and with facilities to arch and bend our profiles, we can produce units that provide as unobtrusive installation as possible, whilst you retain all of the original characteristics of the building.

Offering bespoke colours and finishes, to blend seamlessly into the surroundings, so that you benefit from the thermal or acoustic insulation without losing any of the charm and beauty of the existing period features.

Click on any of the below buttons to download the PDF 

Eliminating Draughts
Secondary Drawings
Easy Clean Vertical
Hinged Sec. Drawings
Sec. Frame Dimensions
Sound Reduction
Sound Reduction 2
Spec sheet
Energy Efficiency
Measuring Guide


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