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Secondary glazing windows guide

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Secondary glazing is a smart and efficient way to enhance your home’s insulation. 

Fitting this to single glazing is typically straightforward and requires minimal alteration to the original windows. It’s an excellent option for listed buildings, homes in conservation areas or other buildings where replacing windows is prohibited or tricky to receive permission for. 

Read on to learn more about secondary glazing, costs, potential savings and steps to get a quote.

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What is secondary glazing?

Usually, secondary glazing is installed in houses that are unable to swap single for double glazing, in order to preserve the architecture or character of the design.

Secondary glazing involves installing new, fully independent glass or plastic panels on the interior of an existing window. This creates an air gap between the original window and the secondary layer, enhancing thermal and acoustic insulation. Think of it as installing a window behind your original window. 

While secondary glazing doesn’t create the same airtight gap you’ll find in double or triple glazed windows, it still vastly improves the thermal performance of the original window, particularly if it’s only single glazed. 

Modern secondary glazing keeps a low profile when viewed from the interior and won’t affect the exterior appearance of your home.

Benefits of secondary glazing

So, what are the benefits of secondary glazing, and when is it worth considering?

No changes to your property’s exterior or existing windows

Secondary glazing enhances your home’s insulation and soundproofing without replacing or altering the existing windows. 

As it’s applied internally, it won’t impact the exterior of your property, which is ideal for historical and listed buildings, properties built in conservation areas and period houses where planning regulations restrict altering the original windows. 

Historic England, the executive department for listed buildings in England, recommends secondary glazing for listed buildings where consent would be otherwise required to replace the windows. 

Secondary glazing is a unique solution for increasing energy efficiency in period or otherwise protected properties with poorly insulated single glazing, such as cottages or Victorian terraces. 

Better insulation

Secondary glazing enhances thermal insulation. It creates an additional barrier that effectively reduces heat loss in winter and limits heat ingress during summer.

Applying low-emissivity secondary glazing to a property reduces heat loss through the window by 60 per cent.

This is particularly valuable in older buildings with single glazed windows where heat loss through the windows can be an issue in winter. 

Less condensation

Poorly insulated single glazed windows create a steep temperature gradient between the interior and exterior of the property. 

This can lead to condensation and dampness on the inside of the window and around the frame, often resulting in mould and damp problems. 

Secondary glazing effectively prevents condensation on the interior window surfaces, reducing the risk of dampness and mould. If your single-glazed windows contribute to dampness and mould, then secondary glazing can be an effective solution. 

Condensation can ruin timber windows and increase maintenance costs. (Adobe)

Reduced costs

Opting for secondary glazing is typically more economical than full window replacements. 

It offers a budget-friendly way to upgrade window performance without the significant expense and labour involved in installing new double or triple glazed windows.

Security benefits

Adding a secondary pane to your windows enhances security. High-quality secondary glazing is thick and durable, with locking systems much like a standard window. 

The extra layer acts as a deterrent against potential break-ins, making it harder for intruders to gain access. Some secondary glazing uses toughened glass to further boost security. 

Noise reduction

Secondary glazing is highly effective at reducing external noise. It acts as a sound barrier, blocking noise from traffic, neighbours, busy areas, clubs and pubs, airports and railways. 

Easy installation and removal

Secondary glazing can be relatively easy to install and uninstall without affecting existing window sills, walls and windows. Installation costs are low, and you can even take secondary glazing with you when you leave the property. 

Secondary glazing window types and styles

Secondary glazing comes in different styles, from temporary, cheaper options such as magnetic glazing to permanent sliding or hinged models. 

Here’s an overview of the main choices:

Lift-out secondary glazing

Lift-out secondary glazing features a pane that can be easily removed from its frame.

There’s no means to open the window other than lifting the entire secondary glazing pane. It’s a cheap and simple but relatively inflexible means of adding secondary glazing to a window. 

Magnetic secondary glazing

Magnetic secondary glazing involves attaching a secondary pane of glass or plastic to the inside of an existing window using magnetic strips. 

It’s quick and convenient, enabling homeowners to add secondary glazing without the need for extensive modifications to the existing window frames.

The magnetic strips make it straightforward to detach and reattach the pane as needed, offering flexibility for cleaning and maintenance or during warmer months when additional insulation is unnecessary. 

DIY magnetic secondary glazing is very cheap, but it’s not a permanent solution and will provide limited insulation compared to professional secondary glazing.

Better than nothing? Sure, but if you have a single glazed property and need to upgrade the windows without replacing them, then sliding or hinged secondary glazing is more effective. 

Horizontal- and vertical-sliding secondary glazing

Horizontal-sliding secondary glazing features panels that slide horizontally, allowing easy window access for cleaning or ventilation. It’s best suited to wide windows. 

Vertical-sliding secondary glazing is designed specifically for sash windows

Secondary glazing for sash windows preserves the classic functionality of the original sash design, allowing the secondary pane to move up and down just like the primary sash window. 

Sliding secondary glazing is a more permanent, effective solution than lift-out or magnetic glazing. Consider this if you need a high-performing, long-lasting upgrade. 

Hinged secondary glazing

Hinged secondary glazing offers the ultimate flexibility in terms of access and cleaning. This type can be opened like a regular casement window, making it suitable for a variety of window styles. 

Hinges are available on the side, at the top and at the bottom of the windows, each catering to different accessibility needs. 

Like sliding secondary glazing, this is a more permanent option designed to give full access to the original windows. As with sliding windows, consider this if you need a high-performing, long-lasting upgrade.

How much does secondary glazing cost?

The cost of secondary glazing varies, with quality hinged or sliding secondary glazing ranging between £300 and £500 per single casement window, including installation. 

Cheaper magnetic secondary glazing costs less, with budget options coming in at around £200 or less per window for temporary DIY secondary glazing kits. 

All things considered, a typical three-bedroom house with 8 to 10 windows would cost between £3,500 and £5,000 for high-quality sliding or hinged secondary glazing with installation​​.

Secondary glazing type Cost per window Total cost for 8-10 windows
Magnetic £100–£200 £1,200–£1,500
Lift-out £300 £2,400–£3,000
Horizontal sliding £350–£500 £3,500–£5,000
Vertical sliding £350–£500 £3,500–£5,000
Hinged £350–£550 £3,500–£5,500

Potential energy savings with secondary glazing

Based on a 60 per cent reduction in window heat loss versus single glazing, homes with secondary glazing can expect to save around 10 per cent on energy bills. 

These savings are most significant during colder months, as secondary glazing helps retain heat, reducing the need to run heating systems for extended periods​​. The colder your property and the more costly it is to heat, the higher the savings.

Getting a quote for secondary glazing

This horizontal sliding secondary glazing is from Anglian. (Anglian)

Many leading window installers and home improvement companies, along with local installers and glaziers, offer secondary glazing. 

Research reputable suppliers

Begin by researching and identifying reputable window suppliers. Look for companies with a strong track record, positive customer reviews and expertise in secondary glazing. 

Today, many leading window installers, such as Everest and Anglian, offer secondary glazing. 

Everest, one of the most well-known window companies in the UK, offers a range of high-quality, made-to-measure secondary glazing products optimised for insulation and soundproofing. 

Anglian, another prominent name in the industry, offers thermally efficient, soundproof secondary glazing. 

Contact your shortlisted suppliers for an initial consultation. Many companies offer free quotes, which you should take advantage of, as differences in cost can be quite pronounced. 

Get a home assessment and quote

The supplier will typically need to assess your home to provide an accurate quote. 

This assessment involves measuring the dimensions of your existing windows and examining their condition. It’s essential to discuss your specific requirements and expectations with the supplier. This includes your goals for insulation, noise reduction and aesthetics. 

The quote should detail the cost of materials, labour and additional services, such as removal of existing windows or post-installation cleanup.

Getting quotes from multiple suppliers to compare prices and services is highly advisable. Ensure you’re comparing like-for-like in terms of material quality, warranty and the extent of the service offered. 

DIY secondary glazing

DIY secondary glazing is relatively straightforward to install, particularly if you need a quick and simple solution to improve insulation in the winter. 

Secondary glazing kits

These kits are available from many hardware stores and online suppliers. They typically include all the necessary materials, such as secondary glazing film or panels (glass or acrylic), seals and framing. 

Kits vary hugely, from ultra-cheap kits with plastic sheet glazing and magnetic strips to more professional kits with genuine glass panes. 

Before purchasing a kit, measure your windows carefully. Consider the type of secondary glazing that will work best for your home, whether it’s fixed, sliding or hinged.

In most cases, these aren’t permanent solutions and may not look great. However, they’re still handy for sealing a couple of windows in the colder winter months. 

Installation process 

Ensure you have the basic DIY tools and skills required for the installation. 

This may include drills, screwdrivers, sealants and measuring tools. As always, some familiarity with basic home improvement tasks is beneficial.

Each kit comes with detailed instructions. It’s crucial to follow them closely to ensure a proper fit and maximise the effectiveness of the glazing.

Remember to prioritise safety, including using the correct safety equipment, such as gloves and goggles, and being cautious when working with glass or heavy materials.

Be especially careful if you’re altering or changing your existing windows or window frames, and don’t hesitate to seek help if you become stuck. 


Secondary glazing is an economical choice for enhancing home insulation, striking a balance between performance, cost and convenience. 

It’s particularly advantageous for historic or listed buildings, where maintaining the original window is essential. 

Installing an additional glass or acrylic pane inside existing windows improves thermal efficiency, noise reduction and security without major alterations to the property’s exterior. 

In some cases, you may save hundreds of pounds per year on your heating bill.

While there are different types of secondary glazing, the higher-performing and more effective types generally come in at £350 to £500 per window. 

Secondary glazing windows FAQs

Secondary glazing is a reliable method for enhancing window insulation. It matches the lifespan of primary windows when properly maintained. 

Apart from providing additional thermal insulation, it also offers noise reduction. Its reliability stems from its simplicity and durable materials that can withstand regular use without significant wear and tear​​​​​​.

Secondary double glazing effectively reduces home energy consumption, particularly when installed inside poorly insulated single glazed windows. Improving insulation helps maintain a consistent and well-regulated indoor temperature, reducing the energy required for ongoing heating.

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Sam Jeans


Sam is an experienced writer whose expertise lies in home improvements and renewables, as well as technology, where he is especially interested in the world of machine learning and AI. He has written for Vested, Age Times, and the Royal Mint.

For the Independent Advisor, Sam writes about windows and solar panels.


Amy Reeves


Amy is a seasoned writer and editor with a special interest in home design, sustainable technology and green building methods.

She has interviewed hundreds of self-builders, extenders and renovators about their journeys towards individual, well-considered homes, as well as architects and industry experts during her five years working as Assistant Editor at Homebuilding & Renovating, part of Future plc.