Architecture is an interplay of proportion, form and material. And a pragmatic meeting of needs. Architecture is a want and a need. And windows? They are an indispensable part of this struggle for functionality and aesthetics. Architect Perrine Ernest speaks about the key role of windows in the design of façades and buildings.

What is the role of the window as an architectural design element? Perrine Ernest: Glass surfaces are of utmost importance in the design of the building envelope. In contrast to a solid wall, glass reflects – if you like – the absence of material. Windows give a rhythm to surfaces and ensure a certain lightness. Windows are conceptually an important design element of the architectural language. They are the starting point for a whole series of geometrical games and help in composing the structure as a whole. Windows give façades their character and give form to entire buildings.

As an architect, what are the aesthetic criteria that you use when selecting windows?This depends on the particular building and is a function of the architectural style and the specific requirements. The overall result must be harmonious. What can be seen at the moment is a tendency to “delete” window frames. Profiles are becoming thinner and thinner and thus almost invisible. From an aesthetic point of view, however, it can be just as interesting to emphasise the frames and consciously provide accents. For example, you could mark window sashes or highlight them by changing the material.

To what extent do the modularity and materiality of windows influence the architecture?Simply put: our freedom to design increases with the freedom of form. A large selection of materials, colours and structures that can be combined in modular fashion infinitely extends our possibilities. And it is the same for details. From the colour of the glazing beads to the spacers between the panes, the structure of the glazing, its reflection… everything can be individually designed.

But it is always a matter of how the interior and exterior are presented…Yes, for example, windows can frame views or play with perspectives. Large glass surfaces in particular can blur the boundaries between interior and exterior and create a special spatial effect. Small rooms too can be opened with cleverly placed windows and thus acquire a certain amount of space. Light gives form to spaces.

How important are windows for well-being and quality of living?Infinitely important. Windows provide us with light, and we cannot live without light. In addition to indirect natural light, it is also possible to bring direct sunlight into the building by sensible planning of windows. The resulting play of light and shadow in the room changes throughout the day and contributes to the feeling of well-being.

What design trends do you see and where is development heading?Our present is dominated by the question of energy efficiency. Architecture makes an important contribution to sustainability, which can also be seen through the design. The challenge is to keep the energy footprint of buildings as low as possible and to further develop the architectural formal idiom.

How can this be achieved?On the one hand, by selecting recyclable materials that are manufactured in a way that minimises any harm to the environment. On the other, by producing intelligent building envelopes that not only provide excellent insulation but also for example use passive solar energy. But sustainability can also mean developing flexible buildings that change with the demands of use. This way we can avoid having to carry out conversions.

What role does sustainability play when selecting a product?The issue of durability and sustainability is critical when selecting a component today. Other criteria, such as price and technical specifications, etc., are also important, but longevity and sustainability are fundamental to the building envelope.