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Casement Windows Buying Tips

casement windows design (2)

Many residential and commercial buildings are installed with double casement windows. The main reason it is so popular is because of its higher light incidence. The more sashes there are, the more stable the window frame and sash structure. They are available in different materials, shapes, variants, and opening mechanisms for personalized design, and are perfectly matched to your imagination.

different materials of casement windows

What materials are double casement windows made of?

Windows, especially double casement windows with a large force surface, must be able to withstand bad weather. Therefore, stability, weather resistance, durability, and energy efficiency are decisive criteria for choosing window materials. High-quality plastic, aluminum, and strong wood are all available as materials. But what is the difference between the materials and which one is the best? In the following, we will explain in detail for you.


All materials have different advantages. Double casement windows made of plastic get particularly good evaluations for their low price and modern frames. In addition to this, plastic can mimic the color and structure of wood, which gives people more options.


Wooden windows are especially popular with nature lovers. The natural material brings the charm of a real country house into your home. Wood impresses with its good thermal insulation. There are different designs of wooden double casement windows that can be made with different glazes and RAL colors.


Aluminum windows are often used in areas with high-security requirements. Architectural engineering window profiles also prefer aluminum windows. Due to modern construction methods, aluminum easily meets the Building Energy Code (GEG).

Wood-Aluminum Combination

The combination of wood and aluminum combines the advantages of both materials. These modern window frames are stable, insulating and easy to care for, and have a truly natural appearance. This combination is very popular, for example for applications in greenhouses or large window areas.

Different casement window shapes

Different window shapes

Each facade has a different window shape. Due to innovative development and manufacturing processes, even unusual shapes can be achieved. This allows us to install not only stable and functional double casement windows, but also decorative and modern ones. In the design there are usually the following forms of double casement windows.

  • square
  • trapezoidal
  • with slant
  • around
  • triangular

Rectangular or square double casement windows are the standard variants. However, in some areas, such as pitched roofs, skylights, or hill walls, more complex shapes are needed to perfectly match the facade. Then trapezoidal windows, triangular windows, and sash windows are possible. Popular special shapes also include rounded double casement windows. Even lofts can be made livable due to unusual window shapes.

Different variants of double casement windows

In addition to the shape, material, and type of opening, double casement windows can be combined with other elements. Double casement windows with vertical frames or sashes are particularly common.

Double casement window with a central bar

All types of openings are possible for double casement windows with a central bar. Both sides can be tilted or rotated. The mullion stabilizes the frame even when both sides of the window are opened independently.

Double casement window with a central bar

Models without a central bar are called casement windows.

With the window open on both sides, there is no annoying obstacle in the middle and you have an unobstructed view outside. At casement windows, however, the two window sides can only be opened independently of each other. If both sashes are to be fully opened, the tilt and turn sash must be opened.

    locking windowcasement windows without a central bar handles

Double casement window with transom

For a special look, depending on the arrangement, unique designs can be created that are striking for both traditional and modern facades. A distinction is made here between real latticed windows and cheaper variants that achieve a similar impression visually.

Different opening mechanisms

Double casement windows can be opened in different ways. In most cases, both sides of the window open in the same way, or multiple ways.

The following combination options for double-sashed windows are available:

Different opening of the window sides

Same opening on both sides of the window

one wing is glazed, the other can be turned or tilted

both sides are glazed

one wing can be tilted, the other tilted and rotated (only possible with mullion)

both sides can be tilted

one side can be turned, the other can be tilted (only possible with French windows)

both wings can be turned (only possible with middle post)

one side is glazed, the other can be slid (sliding window)

both sides can be tilted and turned (only possible with middle post)


two wings + skylight pane (skylight window)


two wings + bottom light disc (bottom light window)

Effective burglary protection for double casement windows

Effective burglary protection is critical as the rollers of the double sash windows provide a larger surface for burglars to attack. There are special window accessories such as hinged side guards, locking window handles, and tethers. This way double windows are better protected against breaking. In combination with folding and swinging bolts or mechanical locks, windows with alarms are more effective for security. This is a good way to secure double-casement windows without vertical frames.

Security window handles

Dimensions of double casement windows

Windows need standard sizes to be designed for two sashes. Double casement windows are sized based on criteria for masonry, escape routes, light incidence, and window openings.

The following guidelines are applicable to double casement windows.

The height must be at least 375 mm and up to 2250 mm.

The width of the double window must be at least 875 mm and a maximum width of 1375 mm.

Double casement windows for each building

Double casement windows are available in different shapes, materials, designs, and opening types. So there is a suitable option for almost every building. Whether it’s aluminum, wood, or plastic windows, underhung windows, or skylights, at Parlun you’ll find your dream double casement.

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