So much more than meets the eye

The Elbtower’s façade is quite something – and not just to look at

The Elbtower by Chipperfield Architects rises boldly from Hamburg’s silhouette. The elegant and bright tower brings with it a lightness that is in perfect harmony with the Elbphilharmonie – and the façade of the 245-metre-high tower is the reason. What’s more: not only does it fulfil aesthetic functions, but also the highest technical requirements.

The high-rise stands on an exposed concrete plinth, which immediately places the tall building in its urban context. Large window and door openings give structure to the massive base and lend it a special character, allowing views in and out and organising access to the ground floor areas for the public.

The Elbtower rises into the skyline from this base, a filigree glass and aluminium façade that gives the impression of lightness and grace, serenity and stability.

The façade has a twofold structure: a horizontal structure encloses the entire high-rise building. Walkable, open webs form the storeys and divide the tower along its height. Between them, fixed slats span a vertical structure. Both the vertical slats and the horizontal walkways are made of brightly coated aluminium beams, which lend the Elbtower an elegant and welcoming appearance.

Extreme climatic conditions at the site

Towering buildings like the Elbtower have to endure highly variable climatic conditions. Hamburg in particular is known for its rapidly changing weather. Calms and storms, clouds and bright sun, heat and frost all have a direct effect on the building. In order to create a pleasant indoor climate using the most passive means possible, the climatic influences of the environment on the building must be limited to the greatest possible extent.

The Elbtower’s façade is designed with this in mind: several layers of vertical lamellas filter, absorb and reflect environmental impacts. These elliptically shaped slats vary in their size and spacing, allowing them to react to the shape of the floor plan and requirements for sun protection and visual relationships. While deep slats in the south-east and south-west are arranged more densely to accommodate a higher solar input, the slats in the north-east and north-west are more loosely spaced.

This structural sun protection contributes to the multi-layered character and the vitality of the façade: an interplay of open and closed textures is created which changes the appearance of the translucent façade depending on the time of day and the viewing angle. Functionally, the pale hue of the façade also improves the reflection of light between the slats. This ensures that the amount of incidental daylight deep inside the building is comparatively high. The need for artificial light sources is therefore reduced and, at the same time, the well-being and productivity of the users is enhanced.

A thermal envelope

As a result, the space behind the slats becomes a thermal envelope. Having such a construction in front of the façade provides far greater protection against overheating from solar radiation than internal blinds. In addition, rear ventilation and shading help to prevent heat accumulation. This is important for sustainability over the course of the building’s operation. After all, cooling, heating, building services and lighting require a great deal of energy, which leads to correspondingly high carbon emissions over the decades.

Depending on weather conditions, additional opening elements can be integrated to contribute to natural ventilation – and in doing so, to the comfort and sustainability of the building. Moreover, each storey will benefit from one or two pivoting sashes to allow access to the maintenance walkway.

A façade display at the Elbbrücken station

There is, however, often a big difference between planning and reality. In order to demonstrate what the Elbtower will actually look like in three years, SIGNA Real Estate has set up a sample façade element at the Elbbrücken overground station. The façade prototype offers a physical experience – the model can be walked on and also imparts something of the view from the inside to the outside. Because it is made of the same construction materials as the future building, both the visual impression it will have on the public and its functionality can already be ascertained.