Casement Windows Vs Sash Windows

Casement and sash are the two main window styles found on British homes. Between them, they account for the vast majority of windows, from Georgian townhouses and Victorian terraces through to 1960s semis and modern new builds.

Both styles are available in uPVC and timber. Both can be fitted with double glazing for excellent energy efficiency. And both provide good levels of security and weather resistance when properly manufactured and installed.

The key difference is in how they open, and that affects their appearance, their suitability for different properties and their cost. If you are replacing windows and trying to decide between casement and sash, this guide covers the practical differences to help you choose the right style for your home.

Casement vs. sash windows

Energy efficiency

Casement windows have a natural advantage when it comes to thermal performance. The way a casement closes, with the handle compressing the sash into the frame, creates a very effective seal around the entire perimeter of the window. This makes them inherently good at preventing draughts and air leakage.

Sash windows have historically had a reputation for being draughty, and with older designs that reputation was justified. Many period homes with original sashes that rattle upgraded to uPVC casement that damaged the aesthetic of the property.

Modern sash windows are a different proposition. Precision-manufactured frames, double glazing, weatherproof gaskets and brush seals have eliminated the draughts associated with older designs. The difference in thermal performance between a well-made modern sash and a casement window is now relatively small, although, a casement window is still more efficient.

Ventilation

Casement windows can open wide, typically swinging out to around 90 degrees on the hinge. This creates a large unobstructed opening that allows a good volume of air to flow through a room quickly, which is practical for kitchens, bathrooms and anywhere you need to clear steam or stale air. 

Sash windows ventilate differently. Because both the top and bottom sashes can be opened independently, you can create a natural circulation of air through the room. Warm air rises and escapes through the gap at the top, while cooler air enters from the bottom. This is known as stack ventilation and it is one of the most effective natural ventilation methods available employed by period properties.

Security

Modern casement windows are widely considered the more secure design. The multi-point locking system engages at several points around the frame when the handle is turned, and the hinges are concealed within the profile, making it very difficult to lever the window open from outside. Everest casement windows are PAS 24 and Secured by Design accredited.

Sash windows have historically been considered less secure because the sliding mechanism can be more vulnerable to forced entry. However, modern sash windows have addressed this with multi-point locking systems and security restrictors.

Cost

Casement windows are less expensive than sash windows. The design is simpler, manufacturing is faster and installation is more straightforward. A white uPVC casement window is the most economical window you can buy, making casement the natural choice when budget is a factor or when there are a large number of windows to replace.

Sash windows cost more because of the complexity involved in their construction. The sliding mechanism, the balance system and the precise tolerances required during manufacturing all contribute to the higher price. Timber sash windows are the most expensive option.

A house that was built with sash windows will look its best with sash windows, and the architectural integrity they bring can contribute positively to the value of the property. Replacing original sash windows with casement to save money can have the opposite effect and may make the property less desirable to future buyers.

Which style suits your property?

This is often where the decision becomes clearest, because the right window style is closely tied to the age and character of the building.

Sash windows are the defining feature of Georgian and Victorian architecture. If your property dates from any of these periods, sash windows are almost certainly what the house was originally built with. They suit the tall, portrait-shaped openings found on period properties and create the classic proportions that give these streetscapes their character. Replacing sash windows with casement on a period property can look out of keeping with the building, disrupt the balance of the facade and potentially reduce the value of the home.

Casement windows are the standard for most 20th and 21st century housing. They suit 1930s semis, post-war estates, bungalows, modern new builds and contemporary architect-designed properties. For cottages and rural homes, casement windows with Georgian bars or leaded glass can recreate a traditional appearance that is sympathetic to the style of the building.

If you are unsure which style would work best with your property, our guide to the different types of British houses looks at the architectural styles found across the UK and recommends the windows and doors that work best with each. 

Which window should you choose?

Choose casement windows for modern properties, 1930s or later semis, new builds, cottages and any home where casement is already fitted or in keeping with the architectural style. They offer the best combination of energy efficiency, versatility and value, and are available in uPVC, timber and aluminium to suit most tastes and budgets.

Choose sash windows for Georgian and Victorian homes where you want to maintain or restore the original character of the property. Sash windows are often a requirement in conservation areas and for listed buildings. Modern sash windows combine the period aesthetic with contemporary performance, so you no longer have to compromise on warmth or security to get the look you want.

If you are unsure, our guide to the different types of British houses can help you identify which windows and doors are best suited to your property.