What are the parts of a window?

Usually the questions that seem to have a simple answer are the ones that hide more complications. We can all quickly get an idea of what a window is and define it with greater or lesser difficulty.

However, and in this we surely agree, when we think of all the pieces and parts of a window we surely do not find it so easy anymore. After all, windows have evolved step by step with architecture and, nowadays, they are pieces of engineering.

This is because, in addition to their ancestral function of illuminating and ventilating a room, nowadays windows are one of the key elements of the building envelope and their correct installation and insulation can help us to save a large percentage of energy.

In this post we will know not only the parts of a window, but also the most common materials used in its construction and the most popular types.

Types of windows, the taste is in the variety

As we have mentioned, windows have been part of homes since ancient times. Therefore, they have evolved with them as the technique improved and new technologies arrived.

This step by step evolution has allowed the development of different types of windows and accessories, such as blinds, curtains, shutters, etc. Nowadays we can find different types of windows, such as:

horizontal slider window

Horizontal slider

Sliding windows are what usually come to mind when we think of windows. They consist of two sashes resting on rails that move left or right. There are different types of sliding windows, such as folding or lifting windows.

Casement window


Casement windows are those that open on a fixed axis, using the fittings located on one of the sides of the sash. They offer better insulation than sliding windows, as they close under pressure and allow the hole to be opened completely

Single hung window

Single Hung

Sash windows move on their vertical axis and usually consist of two sashes. When the opening is opened, these are superimposed. There are different types of sash windows.

pivoting window

Pivoting windows

These windows pivot on a vertical or horizontal axis integrated into the frame. They do not reveal the entire opening and are often used on roofs, where other types of window are more complicated to handle.

Tilt and turn window

Tilt and turn

Tilt and turn windows have gained popularity in recent years. These windows combine the functions of vertical (opening up to 45°) and horizontal (opening up to 180°) pivoting windows, so they can open in two different directions depending on the needs of the moment.

picture window

Picture window

They are made up of a single, inoperable blade. Their only function is to allow light to enter. An example of a fixed window is a porthole

Parts of a window. A technological process

As we were saying before reviewing the different types of windows, nowadays windows consist of many different parts, each with a different function, to make the whole as efficient as possible.

Energy efficient insulation means eliminating as far as possible any water or air leaks that may enter through the windows, which are the weakest elements of the building envelope.

For this reason, windows today have different layers and materials along their structure, in addition to the mechanical action of the hardware.

Common materials


Traditionally, wood was the most common material for windows. It used to be treated with varnishes and paints to improve its durability. Nowadays it is still used, but it is much less common.


Steel is a very resistant material that is often used for large windows. It is a durable and easy to clean material, but it must be treated to ensure its durability over time

PVC (Polyvinyl chloride)

Due to its excellent properties, PVC is one of the most widely used materials for building windows. It is a material with low thermal conductivity, its life span is long and it is totally recyclable.


As we saw in the post about aluminium, its properties have made it the most widely used material for window construction. Its lightness, recyclability and long life cycle thanks to its resistance to corrosion have made it the ideal product.

Basic elements of a window

As you can see, there are several parts that make up a window and make it more efficient. From the type of glass to the seals and, of course, the fittings, form the whole of a system that is more complicated than it may seem.

Glass and air/gas chamber

There are different types of glass, which are used according to the function of the window.

  • Single glass: The most classic and already practically in disuse due to its low acoustic and thermal properties. It is composed of a single sheet
  • Glazing with double/triple glazing: están formados por dos o tres hojas separadas por una cámara sellada. Mejora el aislamiento térmico.
  • Safety Laminated Glass: its main feature is safety. It consists of two sheets of glass joined together which, in the event of breakage, do not spread but remain joined together. It is the type of glass used in car windscreens or armoured glass.
  • Low-E Glass: consists of double glazing. Each of the layers is treated with a low emissivity treatment resulting from the application of silver-containing metals. They are especially recommended for areas with a high incidence of sunlight, for which they are specially treated. They also help to preserve the heat inside the home

Parts of a window - type of glass

The resulting chamber between the glasses in the case of double or triple glazing is usually filled with dehydrated air or gas. This treatment manages to improve the U-value of the glass, which refers to the flow of energy through the window.


The window profile is the material used to house the glass and other components. Not to be confused with the frame, as there may be a situation where one material is used for the profile and another for the frame.

In short, the profile is the moving part of the window. It is connected to the frame by means of a hinge system and has the hardware and thermal break system inside.


The seal is one of the key elements of the window. Its purpose is to ensure contact between the profile and the glass, reducing the amount of air and water that can filter through the window.

For extrusion of window seals, different materials are often used, such as EPDM, a type of high quality and durable synthetic rubber, ideal for thermal insulation. EPDM can be extruded in various hardnesses and shapes.

Likewise, PVC and TPE (thermoplastic elastomer), are two other materials guaranteed to be used as waterproof joints due to their properties and dimensional stability, which prevents the deformation of the piece.

The use of silicone is also popular, but it is more suitable for the industrial sector because of its properties as an electrical insulator.

parts of a window - sealing


It is the part of the window that joins the wall with the profile. It is divided into a crossbar, which are the horizontal profiles, and a mullion, which are the vertical ones


The hardware is the set of pieces that make it possible to open or close the window. In fact, there are the key parts of a window, whether it is a sliding, hinged, tilt and turn or pivoting window.

At present, few fittings are exposed on a window, as they usually go inside the profile.

  • Window channel: This is the channel in which the opening and closing mechanisms are inserted. The current standard size is 16 mm
  • Hinges, that make it possible to open or turn the window. Depending on their characteristics, they can be adjusted laterally or vertically and can be used for internal or external openings
  • Cremones, are a series of rods which, by operating their mechanism through a handle, are responsible for closing the window. They incorporate guidance systems with compression springs to indicate the turns every 90º or key lock
  • Handles, is the classic element of windows. It works as a lever or handle and operates the window’s closing mechanism
  • Casement window hardware. They include a series of parts such as pins, terminals, plates, etc., which allow for progressive regulation of the enclosure.
  • Tilt and turn. For this type of window, hidden hinges are used for vertical and lateral adjustment and with recessed sliding areas to improve the smoothness of the mechanism
  • Folding and projecting. For this type of window, limiting compasses (a compass is a part that limits the opening of the window) and pressure closures are important
  • Sliders. Sliding windows incorporate multi-point locks to improve security and watertightness, as well as security locks to keep the window closed and prevent removal
partes of a window - hardware

At this point, we will terminate this post. If you want to know more about the parts of a window, such as the seals or fittings, I recommend that you visit www.stacmid.es and https://www.stac.es/paginas/inicio where you will find information, catalogues and technical data sheets on this type of product.