What’s the difference between double glazing and secondary glazing?

If you are lucky enough to have sash windows in your home, you’ll already appreciate the style and practical beauty that they add to a property. New sash windows from Ventrolla are bespoke and are thermally efficient to keep your home toasty-warm.

If you have a period sash window, you may find they are inefficient by today’s standards at keeping your home protected from the cold. There are two options if you would like to upgrade your sash windows keeping the existing frame: secondary glazing and double-glazing. But what are the differences and benefits of each system?

Double glazing

Double glazing a sash window involves replacing the individual panes of glass with high-quality slimline double-glazed panes. These panes will not only improve the eco-efficiency of your home, they also improve sound insulation and security.

close up sash bay window
bay sash window

Secondary glazing

Where double-glazing is not an option (this may be the case in a listed building or a conservation area), secondary glazing can be just as effective. Secondary glazing is a second, independent aluminium framed window fitted on the room side of your existing sash window. These are a great alternative to double glazing as they make your room warmer, improve sound insulation and security. They can be hinged or slide to open on warm days.

open sash window
bay sash window


Whichever solution you choose, both double and secondary glazing are sure to improve the efficiency of your home without the cost of installing new windows. Ventrolla can provide quotes and advice on glazing options for your home. Just contact our team for more information.