What is a dummy sash window?

4 min read Windows

The upper section of a double glazed window unit is often made up of top opening windows adjacent to fixed panes (windows not designed to open). Naturally, the opening mechanism causes an aesthetic discrepancy between the opening windows and fixed panes. As a result, the top windows do not sit level in the double-glazed unit. This won't affect the functionality of the window, however, some homeowners prefer the look of dummy sash casement windows. But what are dummy sash windows?... 

What is a dummy sash window?

Also known as dummy vents, we install dummy sashes to create equal sightlines between top opening windows and fixed panes. Fixed window panes with ‘dummy’ sashes imitate the look of opening windows, making all the visible panes sit in line. Also known as fake sashes, they only serve a decorative purpose rather than a functional one.

What is a sightline on a window?

Mock Sash Windows in Cream

An equal sightline window is where the windowpanes are all aligned together. So window panes, frames, and glazing bars are in line with each other to create a sleek and clean appearance.

Dummy sashes can slightly reduce the area that lets in light. However, an equal sightline is more pleasing to the eye. So, they're often a preferred choice for homeowners for adding style to a property. It's a small compromise but windows with equal slight lines are sure to add kerb appeal to any home.

Windows with equal sightlines are commonly found in older and period-style properties. Therefore, worth considering if you have an older style of home and require new or replacement windows for listed properties or homes in conservation areas.

Which window styles can have dummy windows?

Slimline windows and composite door in white

Dummy sash windows are most commonly installed with new casement windows, sash windows, or flush casement windows. This is because these window styles are versatile in their designs and can incorporate several windowpanes together for a complete window installation.

Experienced double glazing installers will be able to illustrate a range of window designs that include dummy sashes so you can choose the perfect appearance for your home, whether that be one top dummy window or a set of three to add a bespoke touch. The design options are endless!

Dummy sash windows with decorative glazingslimline uPVC window white internal view

Dummy sash windows are also recommended if you are considering decorative glazing for your new double glazed windows.

Choosing a dummy sash for a decorative window unit ensures the decorative glazing appears the same in each adjacent pane of glass for a seamless design across your home.

Decorative glazing comes in a variety of design choices, including leaded, frosted and obscured glass. So, you can really add a personal touch to your new windows whilst retaining your home's privacy if required.

We install dummy sash casement windows and dummy sash windows in Woking and Surrey


Our team of design experts can help you create truly bespoke windows that fit perfectly with the style of your home. Each and every window we install is bespoke to each property, so you can choose a unique design that meets your individual requirements.

Dummy sash windows are a flexible and simple way to add a bespoke touch to replacement windows, and with a range of window colours, designs and styles, we're a leading double glazing installer you can trust to ensure you get the perfect replacement windows the first time around.

Dummy windows - add a bespoke style to your replacement windows

If you would like help and advice or to discuss your new dummy sash window project with us, contact our showroom today and a member of our team will be happy to help. Alternatively, take a look at our inspirational window image gallery to get some ideas.

Get a free no-obligation quote for new dummy sash windows in Surrey and the surrounding area today!

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“Used the Sheerwater team to replace a couple of Velux windows in our converted loft. Really first class experience, great communication throughout, super professional and the installation was the best we've had in terms of fit and finish and (lack of) damage to surrounding areas. Will use again!”Tim Loake
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