Secondary Window Glazing Explained

Updated onJul 17, 2025

Did you know?

Research consistently shows that inefficient windows can account for up to 25-30% of a home’s heat loss, according to figures from the U.S. Department of Energy.

We are all familiar with double-glazed windows, those popular sealed units designed to boost insulation. But what if replacing your entire window is not possible, or you live in a heritage home where original features must be preserved? There is a clever, cost-effective solution you might not have heard of: secondary window glazing. 

This innovative system fits incredibly behind your existing windows, creating a sealed cavity that acts as an invisible barrier. Anyone looking to eliminate draughts, slash energy bills, and significantly improve both thermal and sound insulation without the fuss and expense of full window replacements by using secondary windows glazing.

Now, this article deeply explores how secondary glazing has become a popular choice for Australians and homeowners worldwide. 

Let’s dive here!

KEY TAKEAWAYS

  • Secondary glazing is a cost-effective way to improve insulation and reduce energy bills by creating a sealed air gap behind your existing windows.
  • It significantly eliminates draughts and provides excellent sound insulation, making your home more comfortable and peaceful.
  • Being much cheaper and quicker to install than full window replacements, secondary units are also removable for cleaning or seasonal needs.

Cost-effective way to save energy

If your windows are structurally sound but draughty, secondary window glazing is the ideal choice. You are never far from a double glazing supplier, wherever you happen to be in Australia. 

Some Australian homeowners report energy savings up to 40% with the help of secondary glazing, which means your climate control system won’t have to work as hard to retain a suitable temperature.

How does it work?

Small timber battens are hooked to the window reveal; the spacing would change depending on the property; windows are unique. A slimline aluminum frame is then fitted to the batons, and silicone is used to create a seal. 

The space between the two windows might be as little as 25mm or as much as 100mm, and this gives you a high level of sound and thermal insulation.

INTERESTING FACT

“Secondary glazing can reduce noise pollution by up to 80%, transforming noisy environments into significantly quieter living spaces.”

Secondary glazing benefits

Great sound insulation

If you live in a noisy neighborhood, secondary windows might be the solution; talk to a local window company about secondary glazing, and they will be happy to provide you with a quote. 

Once the secondary windows are in place, you will be pleasantly surprised at how quiet things are; those annoying sounds, such as the lawnmower, dogs barking, and kids playing in the street, will be noticeably reduced. 

In another case, if you live near a busy main road or a railway line, secondary glazing acts as a very affordable alternative to new double-glazed replacement windows. To learn more, click here and find out about sash window repairs.

Removable Units

The glass panels can effortlessly be removed for cleaning purposes or if you don’t need the insulation for the certain seasons of the year. You have a choice of colors: aluminum, bronze, or black, and the slimline frame does not impact the décor.

Affordability

If you need thermal and sound insulation, secondary glazing is the perfect solution. Since your existing windows are not removed, it is a much smaller project, and installation can be completed in a few hours. 

Not all windows need to be secondary glazed; for instance, if your lounge window is drafty, secondary glazing will stop that. In fact, many Australians have one or two secondary glazed windows to prevent drought. 

That nice armchair you like to sit in gets a draft from the window, so call your local window company, and they will be happy to provide a quote for just one window in your home.

So, there you have it! Secondary glazing is a very affordable backup to replacement windows, and should you be seeking to stop a few draughts in your home, look no further than secondary glazing. It is an effective way to bring modern comfort and efficiency to any home, old or new, without the significant cost. 

You can add that extra layer of insulation and soundproofing, secondary glazing proves that sometimes, the best solutions are the ones that quietly enhance what you already have, making your home a quieter and energy-efficient haven.

Frequently Asked Questions
How does secondary glazing differ from double glazing?

Double glazing replaces your entire window with a sealed unit, while secondary glazing adds an extra window behind your existing one.

Is secondary glazing only good for old, draughty windows?

It’s ideal for them, but it also significantly improves insulation and soundproofing for any existing window, even if it’s not very draughty.

Can I open my original windows with secondary glazing installed?

Yes, secondary glazing units are typically designed to allow access to your original windows for opening, closing, or cleaning.

Is it a messy or long installation process?

No, installation is usually quick and minimally invasive, often completed in just a few hours per window without removing your original frames.