Double Glazing vs Secondary Glazing

Choosing the right windows for your home is more than just a matter of choosing the right size. With quality windows, you could massively reduce your energy bills through increased insulation, and you can also effectively block out outside noise when you’re relaxing at home.

The two most popular choices of windows are double glazing and secondary glazing: in this article we take a look at which one’s better.

Double Glazing

Double glazing is composed of two panes of glass with a gap in between them, creating a barrier that effectively insulates your home against the outside elements. The gap between the two panes can either be a vacuum, or is occasionally filled with inert gas such as Argon, which boosts the windows insulative properties.

Secondary Glazing

Secondary glazing is installed via a supplementary pane of glass that is installed on the inside of an existing single-glazed window. The gap between the two panes is therefore larger with secondary glazing, and the supplementary panel is detachable in some way in order to allow the user to open both windows and access the inside panes for cleaning.

So which is better?


Double glazing is the more expensive option, as it requires a new window and must be fitted professionally to ensure a secure fit. Secondary glazing is cheaper as it requires only one additional window pane and can infact be installed yourself, although a poor installation job will incur more costs to fix it later down the line, so this should only be attempted if you have experience in glass fitting.

Sound proofing

Secondary glazing is more effective at sound proofing your home against the outside noise as the larger gap between the two window panes creates a more effective sound barrier. Double glazing does reduce sound pollution, but not quite as effectively.

Energy efficiency

Double glazing is much more effective at insulating a property than secondary glazing due to the stable barrier the fixed gap between two window panes provides. Secondary glazing can be less effective because of the larger gap between window panes and the second pane being removable.

Planning permission

There are no planning permission regulations stopping you from having double glazing or secondary glazing. However, if you are in a listed building, there may be different rules that apply in order to maintain the building’s history. Check with your local planning authority if you are not sure.


Your windows are a big part of your home’s exterior, so regardless of their efficiency, you’ll want them to look good. Double glazing will require a complete window replacement, so if you have a period property with a distinctive look, double glazing can damage the aesthetics of the building. Secondary glazing is a popular choice for this reason, as it isn’t visible from the outside.

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