Double glazing v secondary glazing: everything you need to know

Secondary glazing – sometimes known as secondary double glazing – is a type of double glazing that offers many of the advantages of regular double glazing but with its own unique benefits.

How secondary glazing works

As you may know, double glazing improves your property by creating an insulating air gap between two panes of glass to prevent heat loss – in turn making your home warmer, increasing its energy efficiency and lowering your heating bills.

In sealed-unit double glazing, the two panes are hermetically sealed by a spacer at each edge, and sometimes an inert gas such as argon is used instead of air between the two panes. This provides insulation between the inner and outer panes of glass.

Secondary glazing works on a very similar principle but by creating an insulating air gap between your existing window and a new sheet of glass. Typically, the secondary glazing will be added to the inside of an existing single-glazed window (for UK heritage homes where retro-fitting modern double glazing is prohibited by building regulations), but can also be used to great effect by adding to a home’s ageing double-glazed units, creating a triple glazing effect for an even better u-value.

White secondary glazed unit fitted over old windows to make them more efficient

What is secondary glazing?

Secondary glazing usually comprises a slimline lightweight aluminium window in a single fixed sheet or separate aluminium panes with a sliding insulated joint to allow for cleaning between the glass. It’s available in a huge variety of shapes and sizes, and can be supplied to fit most types of windows.

Because secondary glazing doesn’t require any disturbance to your existing windows, it is relatively easy to install and there’s very little mess or disruption involved.

What does secondary glazing look like?

In the majority of homes, secondary glazing is incredibly unobtrusive and has little or no aesthetic effect on the external appearance of a property. That’s why secondary glazing is ideal for listed buildings or homes within a conservation area, and many planning authorities consider it to be a sensible upgrade. Secondary glazing can even be added to traditional sliding sash windows, discreetly helping to prevent draughts and rattles. Meanwhile, its ability to battle against condensation will help your home for years to come.

Large sliding sash windows with secondary glazing panels fitted over the top for extra efficiency

Does secondary glazing have the same benefits as standard double glazing?

Absolutely: secondary glazing is an extremely effective solution for dealing with noise pollution, preventing heat loss and acting as a strong security barrier against burglaries.

In fact, due to secondary glazing’s ability to be installed at any distance from your original windows, the insulating air gap between the panes can be much greater than regular double glazing – for even greater energy efficiency and helping to combat those rising energy bills.

To find out how your home could benefit from secondary glazing, contact Techniglaze today on 01761 417654 or drop us a message and our friendly expert staff will be happy to help.

Or, download our Product and Performance Guide now

Selectaglaze secondary glazing brochure


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Ali & Fi

We are delighted with the windows, and have already been complimented by our neighbours on the upgrade.

Tyler and Paul were very professional and showed good initiative for the inevitable adjustments that needed to be made. They were particularly considerate of our house, it’s character and our pets! Please pass on our thanks and comments as appropriate.


We are delighted with the windows. As you know we were concerned that they would look different and more “clunky” but really you can’t tell the difference except that the new ones are not falling apart!!! The guys who did the fitting were also good. They were working in freezing fog, really cold but they carried on regardless, they were extremely tidy and cleared up after themselves.

Roy Robinson

I am delighted with the recent installation, it’s good to look out of clear windows. The work was carried out professionally by two excellent gentleman.
I will not hesitate to contact you when I am ready to replace others, also would certainly recommend you to others.

Grant Spicer

Really impressed with the customer service and professionalism from everyone at Techniglaze. Especially liked the follow up call after our doors were fitted to make sure we were happy. Would definitely recommend.

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Dr S Irving

Excellent. This company really care about doing a great job. Roger and Keith have been very helpful and explaining things in detail that a lay person may not understand.

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Excellent customer service, range of products and attention to detail. I honestly can’t rate them highly enough. They stepped in and came to the rescue after Salisbury glass cost us 8 months of time and 100k in increased material costs.

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These guys have been great to us. Helped us out at short notice after we were badly let down by another supplier. We asked for several minor details that were not standard (e.g. different locking mechanisms), and they were flexible and open to ideas. We ended up also commissioning our front door from them; it is super sturdy and beautiful. Always courteous, professional, and good payment terms.

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Adam Barnes

First class service for my window repair, with tricky access issues and a large, heavy glazed unit to install. Really glad I chose this company.

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Jim McGarity

I was looking for a company that could deliver a bespoke pair of roof lights in the Alitherm system. Techniglaze offered the best price and worked with us to ensure the sizes were exactly right and conducted the sales process very professionally. The product is first class and we are exceptionally pleased with the service and product. I can highly recommend Techniglaze.

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