What are the different types of casement windows?

Don't know which type of casement window is right for you? Read our comprehensive guide to the different casement window styles.



Awning-style casement windows are hinged along the top, allowing them to open outwards from the bottom. They're a popular choice for tighter spaces, as well as warmer, more humid areas of the home, such as bathrooms and kitchens.

Their top-hinged design creates a canopy effect, offering weather protection even during light rain. Meanwhile, moisture-filled or stagnant air can escape, delivering pleasant, well-ventilated conditions indoors.

When placed higher up, they can deliver excellent ventilation without significantly compromising on security. When closed, they create an excellent, weatherproof seal that prevents air leakage and helps improve your home's energy efficiency. 

Bottom-hung (hopper) casements

Hopper casement windows are hinged along the bottom edge and open inwards from the top. 

They are ideally suited for smaller areas and lower-level areas, such as basements and utility rooms. Their inward-opening mechanisms allow for controlled ventilation while only creating very limited access from the outside. They're also perfect for spaces where an outward-opening window would create an obstruction to outside areas. 

Their space-saving design offers excellent ventilation, energy efficiency and access to natural light in areas where a standard outwards-opening window would be impractical. 

Flush sash casements

Flush casement or flush sash casement windows are an excellent choice for both modern and traditional homes. Designed to replicate the appearance of traditional 19th-century timber windows, their sash sits flush within the frame for an elegant, classic look.

Thanks to this historically accurate aesthetic, flush sash casements are often approved for installation in listed buildings and conservation areas. 

Much like the side-hung casement, flush sash casements maximise natural light and ventilation around the home. They also allow for clear, unobstructed views of outside spaces and gardens. 

While they lack the overhanging lip of a standard casement sash, this doesn't compromise their weather-resistance. The flush sash casement offers superb protection from the elements. These windows are fitted with a double-rebated seal to prevent water ingress and improve insulation.

Modern varieties also house robust, multi-point locking systems inside their frames to keep your home safe from intrusion.

French/double casements

French or double casement windows are constructed with two side-by-side sashes, each hinged at opposing sides.

This opening mechanism means both windows open outwards without a central pillar (mullion) to obstruct the view. Instead, double casements feature a "flying mullion" attached to one sash. This flying mullion moves with the sash when the window is opened.

Many homeowners choose French casements because they offer abundant natural light, a bright, open feel and good ventilation. They're also favoured by those looking to bring a symmetrical, traditional look to their home.

Their recognisable design doesn't compromise on performance either. Modern double casements boast excellent energy ratings, multi-point locking systems and the potential to function as an emergency egress route. 

Fixed casements

The simplest style of casement window, fixed casements contain no opening mechanisms. Often installed alongside other casement styles, especially in bay windows, fixed casements are extremely durable and easy to maintain.

While they don't offer ventilation, they do allow for plenty of natural light and unobstructed outside views. Modern varieties are exceptionally secure and ideal for hard-to-reach or decorative areas, such as high-level gables.

Casement window energy efficiency ratings

The energy efficiency performance of a window is typically given as a U-value. This is a measure of how effectively building elements (such as windows and doors) transfer heat from inside to outside.

Another important measure is the BFRC energy rating. This measures heat loss on a ranked scale from A++ (best) to E (worst).

So, when looking for energy-efficient windows, you want a low U-value and a high BFRC energy rating.

A modern, double-glazed casement window will typically achieve an A rating on the BFRC scale and a U-value from 1.2 to 1.4 W/m²K.

Calder Windows' triple-glazed casement windows are rated A++ and offer a U-value of between 0.7 and 0.8 W/m²K. With 43% thicker units for better insulation and increased security, they perform with an impressive 40% better thermal efficiency than standard glazing.

Are you looking for energy-efficient, modern casement windows? Calder Windows supplies high-quality casements in a wide variety of styles to customers across West Yorkshire. Why not explore our window range or get in touch for a quick, competitive quote?