Openings structure and define a building and give it a "face". Symmetrically designed perforated façades give the structure a sense of calm, a clear grid of openings lends rhythm and structure, free placement creates excitement. Horizontal banks of windows give the façade a direction and large-scale openings convey transparency. But it is not just the size and dimension of the opening in the wall that is decisive for the building's appearance. Windows and doors that protrude from the façade or are extremely recessed create quite separate effects and recesses that, if necessary, can be used for a specific purpose.
A wall created in a solid construction, with individual, clearly delineated window and door openings is referred to as a perforated façade. This most original form of opening is a result of the technical design conditions that have specified the position and size of the openings within a specific framework since people have been building houses: The size of the openings was determined above all by the materials used to close the openings. Static aspects, the bearing of loads and the formation of lintels defined the outside walls as perforated façades with overlapping openings for centuries.
In the 1920s, Le Corbusier propagated his "five points for new architecture": In addition to the "pilotis", which placed the house on reinforced concrete stilts, the roof garden, the open floor plan and the free façade, the long window (bank of windows) in particular was a feature that immediately defined modern buildings. The semi-detached house in the Weissenhof Estate in Stuttgart, Germany, and the Villa Savoye near Paris, France are examples that show how Le Corbusier replaced the high windows common up to that point with extreme openings. The use of reinforced concrete and a post system allowed the manufacture of this type of opening in the façade, providing significantly better and more even illumination inside the building.
A large-scale opening in the façade that is closed off with multiple window and/or door elements is referred to as a window wall. It can often extend over multiple stories, for example, in stairwells or for the glazing for lobby areas, and is usually designed as a transom/mullion construction. The increased wind forces affecting the static load of the entire construction must not be overlooked. The increased span of the frame profiles also influences the dimensions of the profiles and the type and size of the division of the window wall. In the design, you can work with a deliberate placement of opening sashes in an otherwise large-scale fixed glazing window wall. When planning window walls and the surrounding façade, you must take into account that the glass areas must be accessible for cleaning, and the frame, fittings and any sun protection must be accessible for maintenance. These activities can take place via cradles, ladders, or movable cleaning devices.
The scope for balconies, conservatories and recessed or protruding glazed entrance or habitation areas within the depth of the façade offers further options for façade design. These interfaces can designate spatial crossovers and transitions or form particularly private or particularly public spaces. For example, during the Renaissance, death sentences were announced from the balcony of the Doge's Palace in Venice. However, private openings can also be designed like display windows in residential constructions — mobile shading or privacy protection elements allow the degree of opening to the outside to be determined individually.