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High-Performance Secondary Glazing Solutions
We at CN Glass are a secondary glazing manufacturer and supplier who strive to make your home more secure, comfortable, and peaceful for the long term. Our premises are based in Banbury, right in the middle of the UK, and we deliver across the country.
As a leading UK specialist, we understand that maintaining the aesthetic integrity of your property is just as important as improving its functionality. Our bespoke secondary glazing solutions are designed to provide a discreet, unobtrusive barrier that sits comfortably behind your existing windows, offering better energy efficiency and acoustic performance without the need for disruptive or expensive replacement double glazed windows.
What is Secondary Glazing and How Does it Work Effectively?
Secondary glazing is a practical way to upgrade your windows without the cost or disruption of full replacement. By adding a slim, internal glazed panel behind your existing window, it creates an insulating barrier that improves warmth, reduces noise, and enhances overall comfort without altering the look of your property.
A Smarter Alternative to Double Glazing
Unlike traditional double glazing, secondary glazing doesn’t require you to replace your existing windows. Instead, a discreet internal panel is fitted behind them, creating an insulating air gap that improves both thermal performance and sound insulation.
Because secondary glazing is installed internally, your property’s exterior remains completely unchanged, making it ideal for period homes or properties with planning restrictions.
Engineered for Performance
Secondary glazing works by creating a gap between your existing window and the new glazed panel. This gap acts as a buffer against heat loss and external noise, forming a barrier between the existing glass and the new panel while preserving the visible glass externally.
- Smaller gaps enhance thermal insulation.
- Wider gaps (typically 100–200mm) maximise sound insulation
At CN Glass, each secondary glazing installation is tailored to deliver the right balance for your home.
Reduce Heat Loss. Lower Energy Bills.
With energy costs continuing to rise, improving your home’s efficiency has never been more important. Secondary glazing helps:
- Minimise heat escaping through windows
- Eliminate draughts and cold spots
- Maintain a consistent indoor temperature
The result is a warmer, more comfortable home that relies less on heating, helping to cut your energy bills over time.
Cost-Effective, Low Maintenance
Secondary glazing offers high performance without the cost or disruption of full window replacement.
- No structural changes required
- Quick, internal installation
- Minimal maintenance needed
It’s a practical upgrade that delivers long-term value without the hassle.
Secondary Double Glazing install behind the original frames in a
cottage.
Secondary Double Glazing showing the opening catch to slide and reveal the original window behind.
Secondary Double Glazing is almost unseen
Maximising Noise Reduction and Acoustic Performance
As well as temperature retention, secondary glazing also provides acoustic benefits in reducing noise levels through sound insulation. The external soundproofing provides freedom from noise pollution and improved acoustic performance.
Designed to Block Disruptive Noise
Noise pollution from traffic, aircraft, and urban environments can quickly affect day-to-day comfort. Secondary glazing tackles this at the source by creating a separate internal barrier that interrupts how sound travels into your home.
- Reduces low-frequency noise like road traffic
- Limits high-pitched sounds such as aircraft
- Creates a noticeable drop in overall noise levels
Because the secondary windows are independent from your existing ones, they prevent the vibrations that allow sound to pass through standard glazing, including traditional double glazed windows.
Proven Acoustic Performance
This layered system, combined with specialist acoustic glass, delivers powerful results:
- Noise reduction of up to 80% (approx. 50dB)
- Significant improvement over standard double glazing
- Tailored configurations for different noise environments
With secondary glazing, the result is a quieter, more controlled indoor space, no matter what’s happening outside.
Built for Better Sleep and Focus
Secondary glazing is especially effective in spaces where peace and quiet matter most.
- Ideal for bedrooms, helping improve sleep quality
- Perfect for home offices and focused work environments
- Custom glass thickness combinations to disrupt sound waves more effectively
Each doubled glazed secondary glazing installation is designed to suit your property, ensuring consistent acoustic comfort throughout your home.
Secondary Glazing for Listed Buildings and Period Properties
In period properties and historic buildings, secondary glazing is an alternative to replacement windows and window frames because it does not need planning permission in historic buildings from a planning authority.
For this reason, secondary glazing as an extra pane of glass is often used in Grade 1 and Grade 2 listed buildings, as well as many other types of premises such as schools, colleges, hospitals, universities, hotels, commercial buildings, and offices. It is a cost-effective way to achieve energy savings.
Our secondary window glazing solutions at CN Glass are supplied fully assembled and comprise an aluminium outer frame joined to a seasoned hardwood surround, containing the glazed window. This allows for a neat, unobtrusive installation within the existing window frame and surrounding window reveal, even in the most difficult situations.
A range of hardwood sub-frames and scribing trims for secondary glazing windows can assist in face fixing, reveal fixing and coupling units. This allows the satisfactory refurbishment of large primary windows.
Our Comprehensive Range of Bespoke Secondary Glazing Styles
At CN Glass, we have a comprehensive range of secondary glazing styles to suit just about every application. Our range is designed to work seamlessly with your existing windows and fit precisely within your window frame, based on accurate window dimensions.
Horizontal Sliders
Perfect for wide windows, horizontal sliders glide smoothly from side to side, making them easy to operate and ideal for everyday ventilation.
Hinged Units
Designed to open like a door, hinged units provide full access to your original window. This makes cleaning and maintenance quick and hassle-free.
Fixed Units
A permanent, non-opening option that delivers maximum insulation and noise reduction. Fixed secondary glazing units are best suited for windows that don’t need regular access.
Lift-Out Units
A flexible, removable solution that can be taken out when needed. Lift-out secondary glazing units are ideal for occasional access or where a fully opening system isn't required.
Vertical Sliders
A great match for traditional sash windows, these secondary glazing units slide up and down, maintaining the look and function of your existing window style.
Balanced Vertical Sliders
Engineered for smoother operation, these sliders stay in position when opened, offering improved control, safety, and ease of use.
Tilt-in Balanced Vertical Sliders
Combining practicality with performance, these secondary glazing units tilt inward for easy cleaning from inside your home. They are perfect for upper floors or hard-to-reach windows.
More information on our Slim Heritage Double Glazed units can be found in the following article published by ‘The Listed Property Magazine’.
Managing Condensation and Improving Home Security
One of the most frustrating issues with older windows is condensation. This occurs when warm, moist air inside the home hits the cold surface of a single-glazed pane, leading to water droplets, dampness, and eventually mould growth.
Secondary glazing helps eliminate this problem by creating a thermal bridge. Because the internal pane remains closer to the room temperature, the moisture in the air is less likely to condense on the glass.
Our glass secondary glazing units also add a significant layer of security to your premises. Breaking through a single pane of glass is relatively easy for an intruder. However, having to negotiate a second, independently locked frame made of toughened or laminated glass is a major deterrent.
The additional hardware and sturdy aluminium frames of secondary glazing units make it much harder to gain entry, giving you extra peace of mind when you are away from home.
Technical Insulation Efficiency and Acoustic Testing
Our range of secondary glazing is renowned for its thermal efficiency. Varying degrees of improved thermal insulation can be achieved by using such glasses as Pilkington K and Low E. If the glass is thermally at risk, then care must be taken to specify toughened glass.
The harmful effects of ultraviolet radiation can also be reduced while letting in solar heat, helping to regulate the temperature of your home throughout the seasons. In addition, specialist films can be adhered to the glass to further increase heat insulation whilst adding to the security of the secondary glazing and the premises.
Our secondary glazing units have been tested for sound reduction at the AIRO Acoustics Laboratory (an accredited NAMAS Testing lab, number 0483) in accordance with BS2750: part 3 and BS5821: part 3 1980: 1984, using a purpose-built sound transmission suite.
These rigorous tests prove that our systems are among the most effective on the market. As trusted double glazing suppliers, we at CN Glass don't just promise results. We back them up with data from accredited laboratories.
Whether you are dealing with a busy high street or a flight path, the acoustic performance of our secondary glazing units is verified to give you the quiet you deserve.
A Glass Expert’s Point of View
At CN Glass, we believe in sharing our expertise to help you make the right choice for your home. We aren't just suppliers. We are manufacturers who understand the science of glass. Our factory in Banbury is where the magic happens, and we invite you to explore our technical resources to see the quality for yourself.
A Glaziers Point of View
Double Glazing Traditional Windows
Granada Hu Product Information
Granada Product Information
The Listed Property Show
CN Glass Ltd frequently attends The Listed Property Show in London. We demonstrate traditional glazing techniques where you can come and have a go at face puttying glass into a frame.
Our Heritage Double Glazed Units are produced by us using Edgetech Superspacer warm edge technology and energy efficient glasses with inert gases to fill the air gap. The units will be on display, both glazed into frames and unglazed. This provides the opportunity to learn everything you need to know, see and feel about the products that we are proud to produce in our factory.
Secondary Double Glazing is installed behind existing windows, but no one really wants to see it, so we will have a display to demonstrate just how this is done. Refurbishment of traditional sliding sash windows is very much a balancing game with ropes and weights. This all forms part of the glazing trade factory, and we will be there to demonstrate how we do it.
Secondary Glazing Frequently Asked Questions (FAQs)
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Does secondary glazing require planning permission?
- In the vast majority of cases, no. Because secondary glazing is an internal addition and does not alter the external appearance of the building, it is typically exempt from planning permission, even in Grade I and II listed buildings.
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How much does secondary glazing cost compared to double or triple glazing?
- It is a significantly more cost-effective option. You avoid the costs of removing existing frames, repairing masonry, and the high price of completely new window units. Secondary glazing offers a much faster return on investment through energy savings.
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Can I still open my windows with secondary glazing installed?
- Absolutely. Our range includes sliders and hinged units that are specifically designed to align with your existing windows, ensuring you retain full access for ventilation and cleaning.
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Will it stop condensation completely?
- While no product can guarantee a 100% fix for all damp issues, secondary glazing is extremely effective at reducing condensation by insulating the cold outer pane from the warm indoor air.
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Is secondary glazing suitable for DIY installation?
- While some homeowners choose to install secondary glazing independently using a DIY secondary glazing kit, we recommend professional fitting for optimal performance. Proper installation ensures airtight sealing and maximises both thermal and acoustic benefits.
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How do I measure for secondary glazing?
- To measure secondary glazing accurately, you’ll need precise window dimensions, including height, width, and depth within the window reveal. This ensures the unit fits securely within the window frame.
Ready to Transform Your Home’s Comfort?
Contact our friendly team today for more information or to request your free, no-obligation quote. Let us help you make your home warm, quiet, and secure.
To find out about upcoming show dates and to attend the show for free
Register for tickets in advance by visiting www.lpoc.co.uk/property-show/tickets or by calling 01795 844939.
Let’s get in touch
Contact CN Glass today to arrange a quotation. Reach us in the following options.
Address:
Norton House, Beaumont Road
Banbury, Oxfordshire OX16 1SD
Phone Number: