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So you’re in the market for a new window, perhaps your current window is not insulating your home effectively.

There are so many different window options available to you, it’s confusing enough for anyone. 

Double glazing and secondary glazing are often confused due to both involving two layers of glazing.

However, there is a big difference between the two. 

In this article, we will break down and compare the two types of glazing. Specifically, we will be looking at:

  • The main differences between the two types of glazing
  • The cost
  • Energy efficiency
  • Ease of installation 
  • Planning permission – listed buildings

The difference between double and secondary glazing

What is double glazing? 

You’ve most likely heard of double glazing but what exactly is it?

Double glazed windows are made up of two layers of glass with a gap between them which is either filled with an inert gas, such as argon, or a vacuum. 

To install double glazing, the existing window needs to be removed.

What is secondary glazing?

Often confused with double glazing, secondary glazing refers to inserting of a supplementary layer of glass within an existing single-paned glass window. 

Unlike double glazing, secondary glazing doesn’t involve removing the existing window, and is instead placed on top of the existing window.

Double Glazing vs Secondary Glazing


When deciding between double glazing and secondary glazing, one thing to consider is the cost and which one gives you the best value for your money. 

Double glazing is a considerably more costly alternative to secondary glazing, mainly because double glazing involves fitting an entirely new window. Secondary glazing is added to an existing window. This makes secondary glazing a much cheaper option.


Energy efficiency

In terms of energy efficiency, both secondary and double glazing are desirable options to improve the energy efficiency of your home, saving you money on your energy bills.

However, whilst the more expensive option initially, double glazing can be seen as an investment as it offers twice the effectiveness of secondary glazing in preventing heat escaping your home, saving your money long-term. It may also help increase the value of your home. Double glazing wins this one.

Ease of installation

So, how easy are both secondary and double glazing to install? Secondary glazing only involves the installation of additional glazing to an existing window, whereas, the installation of double glazing means that an entire window must be removed and replaced by a new double glazed window. 

Both are quick work for a trained professional, however, installing secondary glazing is a much simpler process than the installation of double glazing. Therefore, secondary glazing can often be a quicker installation with less mess.

Planning permission – listed buildings 

Usually, planning permission is not required when fitting or repairing a double glazed window.

However, things are different when installing a double glazed window to a listed building, where it is advised to speak to your local planning office before installing to avoid complications.

This is not the case when it comes to installing secondary glazing to a listed building. In this particular case, the exterior of the building is not affected as the glazing is installed internally.

So, if your property is listed, you might want to consider secondary glazing to avoid lengthy paperwork. 

Need double glazing or secondary glazing installing? 

Whether it’s double glazing or secondary glazing you chose, it is important to pick an installer that you can trust. 

At Trade 2 Trade Windows, we are a family run business that is focused on delivering a quality service and providing our customers with the finest quality products.

Through our work, we have gained a prestigious reputation across the southeast of England, including Kent and Rochester.

See our range of windows, or get an online window quote today.

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