Secondary Glazing – Upgrade Your Windows Now

8 min read Windows

Secondary glazing offers a simple and affordable solution, if you’re tired of draughty, inefficient windows that waste energy and boost your bills.

Or your builder have incorrectly installed your double glazed windows and are letting in a noticeable breeze!

By installing a these cost effective solutions on the interior of existing windows, homeowners can upgrade performance without the high cost of a full replacement.

So, Is secondary glazing a good idea?
Absolutely, as you will read on, that with the larger distance between the two frames, it can greatly reduce noice pollution over well over 60% in cases as well as greatly increase thermal efficiency.
Perfect for homes close to busy roads!

What is Secondary Glazing?

It is an independent system that adds an extra layer of glass and framing on the inside of your current windows. A custom-fit secondary glazing system transforms single pane windows into enhanced double glazed ones.

The separate aluminium frame and specialty glass are mounted on the interior window frame or reveal. This leaves your original windows completely untouched on the exterior. It will improve the functionality of existing windows without altering character or charm.

This interior application leaves original facades untouched. The secondary glazing increases glass depth and creates an insulating air cavity between the existing and new glazing. It’s an adaptable retrofit approach that upgrades functionality without alterations.

Secondary Glazing window

An Upgrade for Heritage Homes

Homeowners in older, heritage properties especially face a dilemma – how to upgrade inefficient original windows without compromising historical charm. This system offers an elegant solution. By installing a separate interior glazing system, it’s possible to improve thermal performance, sound insulation, security, and sustainability while retaining the beauty of period windows.

Benefits of Secondary Glazing

Improved energy efficiency

It enhances the insulating performance of windows, reducing heat loss that drives up energy bills. It can lower the U-value, a measure of thermal efficiency, by 1.8 – 1.9 compared to single glazing.

Reduced drafts

Advanced framing and seals create an airtight barrier between the panes that keeps warm air in and cold air out. No more chilly drafts!

Lower carbon footprint

By curtailing heat loss, secondary glazing cuts reliance on heating systems, thereby reducing a home’s carbon emissions. It’s a green, eco-friendly upgrade.

Noise reduction

The added layer of glass buffers interior spaces from outside noise pollution. It will also dampen both street noise and weather sounds like rain.

Enhanced security

Its durable, protective glazing also boosts security and weatherproofing, shielding the vulnerable original windows.

Secondary Glazing window close up

Ideal for Period Homes and Listed Buildings

Offering major benefits with minimal impact on historical aesthetics or fabric. Since it is reversible, leaving original windows untouched, secondary glazing is an approved solution for listed buildings and period homes where regulations limit replacement options.

Often extending the life of existing single glazed windows without alterations, improving function while respecting heritage.

Secondary Glazing window fitting

High Performance Glazing

Advanced glass options and gas fills between panes optimise the insulation, sound dampening, and security provided by secondary glazing. Low-E glass reflects interior heat back into rooms.

Argon gas fills further limit heat conductivity. Laminated and acoustic glass reduce noise penetration. With specialised glazing, secondary systems meet stringent testing standards for thermal and sound insulation.

Secondary Glazing is Cost-Effective

Creating tight seals and barriers against sound, air, heat, and weather, secondary glazing enhances living comforts and efficiency at a fraction of the cost of full window replacement.

For homeowners seeking improved functionality without luxury renovation costs, it’s the optimal affordable solution. Reduce your energy bills and environmental impact while retaining the charm of your home’s original windows with secondary glazing.

Secondary Glazing installation

Secondary Glazing: An Affordable Upgrade

They provide meaningful improvements in efficiency, comfort, and sustainability at a reasonable cost. By retrofitting high-performance glazing inside your existing windows, it’s possible to upgrade their functionality without the expense of full custom window replacement.

For period properties, it is a versatile, adaptable solution that respects history while advancing performance. Unlock the benefits of modern double glazing without saying goodbye to your heritage windows!

Secondary Glazing close up

Window Styles & Designs

We have a selection of window styles and designs to choose from. These include:

  • Hinged and fixed secondary glazing.
  • Sliding secondary glazing.
  • Vertical sliding secondary glazing.

Explaining The Types of Secondary Glazing

Hinged and Fixed Secondary Glazing

This is a popular style of glazing that is the perfect solution for masking hardwood windows that let in draught air. This immediately improves the heat insulation of your home while saving you money on energy bills.

Sliding Secondary Glazing

Sliding glazing options are designed to introduce additional style and comfort to a building. Generally of excellent quality, two popular styles of sliding glazing are vertical and horizontal, the use of which is dependent on the shape and size of your window. The fantastic insulation properties of these glazing options work to save you money on energy bills, while also perfectly matching the style of your home.

Vertical Sliding Secondary Glazing

Vertically sliding glazing is manufactured with guillotine shoot bolts for minor windows and is typically spirally balanced for larger windows. This type of glazing is ideal for windows that are taller than they are wide. It works by half the window sliding vertically over the other half.

This type of unit is most beneficial to listed buildings because they assist in the eradication of draughts while improving insulation. A vacuum between the two units is created, which is similar to double-glazing. This serves to eliminate noise pollution and draughts. Sliding windows may also be sealed with a twin polypropylene weather pile to provide comfort and extra insulation.

Horizontal Sliding Secondary Glazing

Horizontal sliding glazing has a horizontal sliding action, very similar to the movement of sliding patio doors. It works particularly well on windows that are split vertically into 2 panes. In this way, the bars of the secondary glazing are able to match the design of your current window.

This option is ideal for windows that are wider than they are high. Horizontal sliding secondary glazing also provides fantastic insulation and noise reduction qualities. Finished with a twin polypropylene weather pile sealant, you get the peace of mind of knowing that your windows not only look great but are also extremely secure.

Secondary Glazing

Noise Reduction

It is noted for reducing noise pollution and removing the irritation that can be faced from traffic or noise from passing crowds.

The sound test on our glazing measures sounds intensity on dB. The higher the dB the louder the noise. Our secondary glazing glass achieved fantastic results in the reduction of sound. An example being with 4mm glass at 39 dB, there was an estimated

Discreet and Compatible Design

Slimline frames maximise views and allow it to blend discreetly with existing façades. Frames can be painted to match interiors. Since it requires no changes to original windows, it is widely approved for heritage buildings and period homes where regulations limit replacement options. It extends the service life of beautiful old windows without aesthetic compromise.

Is secondary glazing as good as double glazing?

Ultimately, it will be better to suited to some people than double glazing and vice versa. So, we’ve looked at a range of key considerations to help you decide:

Noise reduction

It is slightly better at reducing the amount of external noise coming into the home than double. This is because the gap between the existing window and the secondary glazing is larger than the two sealed panes of glass you find on double.

Planning permission

If you live in a conservation area or listed building, planning restrictions might prevent you from fitting double glazing. In such cases, secondary is the only option if you want to make your home warmer, quiet and more secure.

Secondary glazing cost

It is more cost-effective to fit. However, double glazing is better at retaining heat in the home. Therefore, it tends to provide better long-term savings on your heating bills.

Secondary Glazing window with a sash window


As it requires you to clean 4 panes of glass instead of 2, maintenance times are slightly higher than double.

But no matter whether you prefer secondary or double, we install both here at Sheerwater Glass.

How do you clean them?

Cleaning the windows is very straightforward; all you need to do is wipe them down using warm, soapy water and a non-abrasive cloth or sponge.

The different types of glazing also have their own features to make cleaning easier; horizontal secondary glazing can be removed from the frame; vertically-sliding versions have a contra-slide feature so you can access both sides of the glass.

By Jessica Stevens

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Our customers say

“Used the Sheerwater team to replace a couple of Velux windows in our converted loft. Really first class experience, great communication throughout, super professional and the installation was the best we've had in terms of fit and finish and (lack of) damage to surrounding areas. Will use again!”Tim Loake
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