Building and buying

Types of windows: construction methods, materials and glazing

Torben Schröder

If you have ever thought about buying new windows for your house, then you already know how much choice there is and what a complex subject it is. We have written this article for all readers who are unsure exactly what to expect. We present different types of windows – by construction method, opening mechanism, material and glazing. We also explain what function windows perform with regard to thermal insulation.

View through a window with two sashes and a wooden frame.
© Getty Images

In this article

Types of windows

There are various types of windows that are installed in different ways. We list them in more detail below.

Single window

This type of window is the most common in European households. Single windows consist of casements and sashes and are firmly connected to the masonry. A single window either contains only one pane, or several panes inserted hermetically one behind the other.

Double window

This type of window contains two separate single-pane windows. The inside window opens inwards, the outside window outwards. The resulting gap improves thermal and sound insulation.

Composite window

This type of window is an advanced version of the classic double window. The outer and inner sashes, each with single glazing, move on a common pivot point – in other words, they are structurally connected to each other. When you open the window, only one of the two sashes needs to be moved, the other one “follows” automatically.

Window opening mechanisms

Put the window handle in a horizontal position, pull it and open the window inwards on a vertical axis – you will already be familiar with this mechanism. However, there are a number of alternatives, which we describe below:

  • Fixed glazing: this type of window can’t be opened at all and is therefore mostly used for decorative purposes only.
  • Spin window: this type of window opens using the mechanism described above. The axis of rotation is located either at the left or right edge of the window sash.
  • Tilt window: a similar mechanism to the pivot window, except that the axis is positioned horizontally along the bottom edge of the window.
  • Hinged window: the same principle as the tilt window, except the window is fixed horizontally along the top edge.
  • Tilt-and-turn windows: the most common type of opening mechanism in private households. When the handle is in a horizontal position, you can open the window inwards, and when the handle is in an upright position, it tilts towards you.
  • Sliding window: by operating the handle, this type of window is raised or swiveled out of the guide rail – this allows it to be moved laterally. Sliding windows are used for large, floor-to-ceiling windows. An alternative is when the sliding mechanism is fitted vertically.
  • Pivoting window: this type of window rotates around a horizontal central axis, with one sash projecting into the room and the other sash extending outwards.
  • Reversing window: this works similarly to a pivoting window, except that the window sashes rotate around a vertical axis.
View of a large window in an inhabited room.

Windows play a visual and a functional role. Here is a combination of a floor-to-ceiling window and a tilt-and-turn window in a wooden frame.

Window materials

Window frames are exposed to climatic conditions on the outside – i.e. moisture, frost, UV rays and mechanical influences such as branches flying around during storms. Depending on the room of the house, there may be a high level of humidity inside, for example in the kitchen and especially in the bathroom. This makes the material composition of the frame an important factor. Read more about the options here.

Wooden window frames

As a natural raw material, wood is not exactly the most robust material. However, it is an extremely appropriate choice for a window frame. Wood is still very popular because it looks good – and it is a must for particularly ecologically-minded homeowners.

If you want your window frame to withstand the above-mentioned influences for as long as possible, you should choose a suitable type of wood. Spruce, pine, larch, fir and oak are considered particularly hard-wearing, for instance. You can also fit new windows made of high-grade wood such as maple, alder or cherry. However, these frames age faster and require more care. Regardless of the type of wood, the application of wood protection is essential – both inside and out.

Window frames made of aluminum and wood

Although pure aluminum windows are available, a mixture of aluminum and wood can be an extremely interesting alternative. This composite combines the technical advantages of metal with the visual attractiveness of wood.

Wood-aluminum windows consist of a supporting wooden frame with an aluminum shell on the facade side. Since the two materials expand differently in hot and cold temperatures, they are connected to each other in a floating arrangement rather than being fixed. This means that although they are interlocked by means of a twist-clip holder, they are thermally separated from each other by a cavity.

The aluminum shell on the outside lets wind and weather bounce off – and you have the advantage of the warm wooden look on the inside.

Plastic window frames

Plastic is the most widespread material for window frames. The price of plastic windows is low – plus the material is extremely resistant to external influences and very easy to maintain. Weathering and corrosion are irrelevant; acids, exhaust fumes and cleaning agents have practically no effect on plastic.

Thanks to industrial production, manufacturers offer a wide repertoire of colors and decors. Even in terms of heat and sound insulation, the properties of plastic windows are no worse than those of wooden windows, for example. Two disadvantages are the somewhat cooler living atmosphere and the fact that production is not exactly sustainable.

Close-up of a plastic window with a plastic handle.

Inexpensive and practical: a plastic window with a plastic handle.

Glazing

You have certainly heard of single, double and triple glazing. But what exactly do these terms mean? And what use are anti-sun glass and opaque glass? We explain the different possibilities for window glazing.

Single glazing

For decades, windows only had a single pane of glass. This was simply because manufacturers didn’t know any other window construction techniques. However, as other methods developed and a greater emphasis was placed on energy consumption, it became clear that single glazing was no longer up to date. There are several reasons for this.

Although thin glass is inexpensive and lets a lot of light and heat through from the outside to the inside, it also allows just as much heat to escape back out. This means your heating system must work much harder to maintain the desired indoor temperature. This increases heating costs unnecessarily. Single-glazed windows also offer poor sound insulation and there is a higher risk of burglary, as they are easier to break. Nowadays, single glazing is no longer used in new buildings.

Insulating glazing

This construction method consists of at least two panes of glass, each about four millimeters thick, which are held together by an edge compound at intervals of eight to 20 millimeters. The cavities formed between the panes are usually filled with dry air – this principle ensures good insulation. If the interstices are filled with argon or krypton, the insulating effect is even greater since these noble gases do not conduct heat as effectively as air.

Thermal glazing

A new window with thermal glazing consists of either two or three panes of glass. Depending on the total number of panes, layers of metal oxide are applied on one of the two or two of the three panes, allowing heat to pass from the outside to the inside, but creating a reflecting effect from the inside. This ensures that warm air is kept in the room. The insulation of this type of glazing is even better than that of double glazing.

Anti-sun glass

The main purpose of this type of glazing is to prevent the room from overheating. Wafer-thin layers of precious metal applied to the inside of the outermost pane allow light to pass through as usual, but reflect the invisible infrared light of the sun, thereby reducing heat radiation.

Opaque glass

There are some rooms in which we want to preserve our privacy as much as possible. You should consider installing opaque glass if you have a window opposite the neighbor’s house or facing the street. There are several options available.

  • Frosted glass obtains its typical cloudy appearance from the special substances added during the melting process.
  • The film in laminated safety glass can be colored in such a way that it no longer lets prying eyes see through it.
  • Ornamental glass is another customizable alternative. During production, geometric figures and waves are deliberately worked into the glass so that it is only possible to see a very blurred image through it.
View of a wash basin and two small horizontal windows that are impossible to see through.

Privacy can be preserved in the bathroom thanks to the structures deliberately incorporated into ornamental glass.

Thermal insulation for windows

You have just read that the thermal insulation of a single-glazed window is not as effective as that of two-pane insulating glazing, for example. The thermal insulation of windows can be measured physically – using the U-value, the heat transfer coefficient. Its unit is Watts per square meter and Kelvin. The lower the value, the less heat passes through the window from the inside to the outside. Nowadays, high-performance windows have a U-value of 1 W/m2K. The standard according to Minergie-P is 0.8.

Here is a rough comparison of U-values for the most common types of glazing.

  • Glazing
  • U-value
  • Single glazing
  • 5–6
  • Insulating glazing
  • 1–3
  • Thermal glazing
  • < 1

Various window examples

The rooms in your house and on your property have different purposes and therefore place varying demands on the windows. Here we give you tips on which type of window might be appropriate.

Attics, basements, sheds, summer houses or winter gardens

Ask yourself the following question about these rooms or areas: will they be inhabited, and therefore heated? If you only use your shed as a storage room for equipment and wintering place for plants, then windows with single glazing are sufficient. If you want to use it as a retreat for spending cozy hours in winter, you will have to pay attention to the thermal insulation. An insulated window with a wooden frame is a good choice.

Bathrooms

Depending on how the bathroom window is installed in your home, it’s advisable to use opaque glass. One option is to opt for satined glass, for example. An opaque but translucent effect is created by a mechanical or chemical treatment of the glass surface.

Living rooms

The living room is a place where we want to feel comfortable, relax after work and enjoy the view of the garden outside. When it comes to the windows, the focus is less on function than on appearance. They should also be as large as possible. One possibility is to install floor-to-ceiling windows. They stretch from the floor to just below the ceiling, creating a very spacious feeling and allowing plenty of light into the room. Conversely, you should be aware that there is practically no privacy protection.

Conclusion: the right type of window for every purpose

Not all windows are the same. They vary in terms of construction method, opening mechanism, material and glazing, as well as having different thermal insulation properties. Depending on which room you are currently trying to furnish, it makes sense to install a specific type of window.

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