What Are Secondary Glazing Windows and How Do They Work?
Secondary glazing windows are an additional glazed unit fitted on the inside of your existing windows. Rather than removing or replacing your original windows, a slimline secondary frame and pane is added behind them, creating a new insulated “layer” that works alongside the original glass.
Key features
- Secondary glazing consists of a separate internal sash or pane that is fitted within the reveal of your existing window, creating an additional layer.
- The frames are typically made from aluminium, offering a slim, durable profile that’s both strong and low-maintenance.
- This solution is often reversible and minimally invasive, making it ideal for older or listed buildings where replacing the external windows could be disruptive or restricted.
Types of Aluminium Secondary Glazing Windows
Vertical Sliding Secondary Glazing
Ideal inside traditional sash windows. Our vertical sliding secondary glazing operate with spring balances, supporting the weight of the sash in all positions. These windows have a tilt facility to allow the panes to be tilted inwards, allowing easy access to clean the inside of the primary window.
Horizontal Sliding Secondary Glazing
Our horizontal sliding secondary glazing is mounted on rollers, providing a smooth, easy operation. Ideal for spaces where you need convenient access and adjustable ventilation, whilst improving comfort and efficiency. Horizontal sliding units are generally available in 2, 3, 4 or 5 panel versions.
Hinged Secondary Glazing
A practical and versatile option, hinged secondary glazing opens like a standard casement window. It allows for easy access to the outer window for cleaning, ventilation, or maintenance, while still delivering excellent thermal and acoustic insulation.
Benefits Secondary Glazing
Improved insulation
Aluminium secondary glazing significantly improves the thermal performance of your home by trapping an extra layer of air between the primary window and the secondary glazing. This added barrier helps to reduce heat loss and cut down on draughts, maintaining a more comfortable indoor temperature all year round.
Soundproof Windows
Secondary glazing is the best way to sound proof your windows and help block out external noise from traffic, railways, or busy streets. Giving you a quieter, more peaceful home.
Secondary glazing with an air cavity of at least 100mm can provide noise reduction of up to 45dBA. As the gap increases higher levels of sound insulation are achieved.
Unlike double or triple glazing which legally require trickle vents, aluminium secondary glazing is fully sealed, offering more effective sound reduction.
Built to last
Made from high-quality, weather-resistant aluminium, these windows are designed to withstand the test of time. With minimal upkeep required, your windows will retain their looks and functionality for years.
Cost-effective
Secondary glazing is more economical alternative to full window replacement. It’s ideal for period or single-glazed windows, providing many of the same insulation and noise-reduction benefits as double glazing without the disruption, extra costs, or loss of character.
Ideal for conservation areas and listed buildings
Secondary glazing is a discreet, internal solution for properties in conservation areas or listed buildings. It can be fitted and removed with minimal disruption, improving comfort and efficiency while preserving the home’s original exterior and character.
Low maintenance
Aluminium requires minimal upkeep. A quick wipe with warm, soapy water is all it takes to keep your windows looking as good as new. The durable powder-coated finish ensures your secondary glazing retains its colour and finish without needing to be repainted.
Secondary Glazing vs. Double Glazing
When deciding between secondary glazing and double glazing, it’s important to understand how they differ and which option best suits your home. Both improve comfort and efficiency, but in different ways.
Cost and installation
Secondary glazing is often more affordable than replacing all your windows with new double-glazed units. It’s fitted internally over your existing windows, meaning less disruption, no need for building work, and a perfect solution for period or listed properties where full replacement isn’t possible.
Noise reduction
If reducing outside noise is a priority, secondary glazing performs exceptionally well. The larger air gap between the primary and secondary panes, combined with the absence of trickle vents, helps to reduce external sounds more effectively than standard double glazing – ideal for homes near busy roads, railways, or city centres.
Thermal insulation
Both secondary and double glazing improve insulation and reduce heat loss.
Double glazing benefits from advanced engineering, such as gas-filled cavities and Low-E coatings, and carries official BFRC energy ratings.
Secondary glazing, however, creates a larger insulating air space, which helps to keep warmth in and draughts out – though its performance depends on the type of existing window behind it.
Flexibility and heritage
Secondary glazing is an excellent option for homes in conservation areas or with original single-glazed windows, as it preserves the property’s appearance while delivering modern comfort. It can be installed and removed with minimal impact on the building’s structure or style.
Secondary Glazing FAQs
Yes, our aluminium secondary glazing windows provide exceptional insulation, significantly reducing heat loss and improving energy efficiency in your home. This can result in a more comfortable living environment and reduced heating bills.
For secondary glazing, we offer obscure glass to provide privacy while still letting light through.
The aluminium frames of our secondary glazing windows come in a clean, classic white finish, a timeless choice that complements any home style and interior décor.
Aluminium is a strong, durable material, and when properly maintained, secondary glazing can last for a long time, up to decades. Because secondary glazing is installed on the inside of your existing windows, it’s less exposed to the elements than standard aluminium windows, which can help extend its lifespan.
It’s important to note that condensation can occasionally form between the secondary glazing and the original window, particularly on older single-glazed units. Regularly checking and keeping the space clean will help preserve both the secondary glazing and your existing windows, ensuring long-lasting performance and appearance.
Why Choose Safestyle?
Made in Britain
All our aluminium secondary glazing windows are manufactured in the UK to the highest standards, ensuring exceptional quality and performance.
Price Promise
With our price guarantee, we’ll match any like-for-like quote, so you can be sure you're getting the best value with the best quality.
10 Year Guarantee
We stand behind the durability and quality of our aluminium secondary glazing windows. That’s why every unit comes with a 10-year guarantee, giving you long-term peace of mind.
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