Standard sizes of single leaf windows are as follows:
For single leaf windows there are ten different widths of window and ten different heights of window, giving a total of 100 different combinations.
However, it is not always so that the window must be higher than it is wide. Window sizes in rooms such as storage rooms, cellars or also in attics are often of a different size. In these cases it is also standard that the windows are wider than their height.
Single pane windows are more frequently found in smaller rooms in contrast to double-sash, as the former have a smaller surface area or shorter wall space.
The standard sizes of double leaf windows are as follows:
For double panel windows there are fifteen different window widths and ten different window heights available, giving a total of 150 different combinations.
For a double panel window there is a mimimum size of wall which will accommodate a particular window.
These window sizes are often found in living rooms starting from circa 20 qm and, once very popular, also in kitchen-diners or kitchen-living rooms.
In some countries there may be legal restraints on windows, e.g. in Germany only 1/10 of the width of a room may be window space or 55% of the internal space. In the United Kingdom it is merely recommended that the total window area should be greater than 20% of the floor space for reasons of lighting. However, as individualism plays a major role in planning and building, there is also a great need for special shapes and sizes when it comes to windows.
Special window shapes are very often chosen for their decorative element rather than for purposes of lighting or air flow. Small window sizes, which vary from the standard sizes, are very often used to provide sufficient air and a minimum of lighting to a smaller room such as a junk room, utility room, pantry or small cellar room. However, it is not just these auxiliary rooms which require special sizes when it comes to windows.
Often one finds these in bathrooms, for example where the bath tub is positioned below the window, or where a larger window would enable too much visual invasion of privacy. In all the above-mentioned areas it could lead to smaller windows being selected, i.e. smaller than standard.
However, the opposite can also be true. Panorama windows for example, which are designed to provide a very light and airy living space. In this case, one often designs a size of window that will fill the complete heigth and width of the available wall.
In the same way there is sometimes the requirement for special sizes when it comes to the commercial sector, e.g. in the design of a display window or to provide light to a show room. Large car dealerships are a good example of this, but small and medium-sized boutiques in the shopping areas are others.
Of course, it is not always a question of special shapes and unusual sizes. The three-fold window opening is popular and to a lesser extent windows with four sash elements. Windows comprising three elements are seen in country areas, where these windows are often found in kitchen-dining rooms. Finally, it should be said that when it comes to windows everything is possible if you like it. The requisite window size or shape can be found even to satisfy the most unusual wishes, whether as a standard solution or as a special size or made to measure.