Office Building Müllerstrasse
This project began with an existing office building from the late 1970s. To address the outdated infrastructure and meet the changing needs of the new tenants, the project required a fundamental modernization of the building structure and building envelope. The goal was to redesign the existing building by preserving its structure while adapting it to modern needs.
The approach of circular construction – the reuse and strategic further development of existing materials and structures – was a pivotal aspect of the project. The basis for this was an analysis of the building structure and the materials used, in order to identify their potential for future uses.
The existing facade was characterized by a grid of large cast aluminum claddings and extensive glazing. From the outside, they give an impression of openness, however, on the inside, they did not match the external appearance. The lower third of the glass was obscured by a concrete parapet, which was located behind mirrored spandrel glazing. The external generosity and openness of the facade was reduced to a standard dimension on the inside, creating a blatant contradiction. To resolve this aesthetic and functional discrepancy, the new facade was designed in such a way that it establishes a balance between interior and exterior openness.
First, the existing building components were dismantled down to the main supporting structure, and the structure was optimized. The concrete parapets of the building were removed to create an open spatial effect. Parts of the these were reused as seating benches. The remaining material was recycled and used again as aggregate for recycled concrete and terrazzo flooring. A tension rod system replaced the concrete parapets to prevent deflection of the ceiling edges caused by their removal. The tension rods were arranged within the grid of the new facade and suspended from a steel beam filled with concrete, which rests between the 6th and 7th upper floors and transfers the forces into the main supporting structure.
The original supporting structure of the building showed irregularities in its axial dimensions. In order to nevertheless achieve an economical and low-maintenance solution, a system consisting of facade elements with a limited number of varying widths was developed, which visually compensated for the deviations in an inconspicuous manner. This allowed for the minimization of the element and glass sizes used, which made the manufacturing process more efficient and saved costs and energy. This principle was also applied to the height of the glazing. The dimensioning of a base element on the ground floor and a closed facade element above it (on the ground floor and 6th floor) determined the glass heights on all floors, which contributed to a harmonious facade design.
The new facade resolves the previous contrast between external spaciousness and reduced interior effect. An open design and dynamic lighting now create a balanced effect that meets the requirements of modern office use. The nature of the old cast aluminum panels (composition and contamination of the alloy) made it impossible to produce new aluminum profiles from them and to recycle them in this way. Therefore, they were largely reused directly. They were recut using water jet cutting, cleaned, and installed as cladding for the new facade. The cast aluminum panels were subsequently not glued, but welded to a supporting structure and hung on the facade. This allows them to be removed more easily in the future, simplifying recycling processes. This approach saved all the grey energy that would have been necessary for melting down and reforming the material.
The leftover material from the cutting process was made into wall and ceiling cladding for the two main lobbies on the ground floor (the panels were finely sanded and joined seamlessly). Signage plates for the wayfinding system of the extended basic fit-out were also produced in this way and installed in the staircases, sanitary areas, and elevator lobbies. All remaining material that could not be used otherwise was melted down and utilized for aluminum panels on the inner courtyard facade. The entire facade was equipped with dynamically controllable liquid crystal glass with a heat protection function.
The elements can darken within seconds but do not restrict the unobstructed outward view, which is essential for well-being. The system reacts to even low and diffuse heat input with partial dimming, thus efficiently preventing overheating. The specific ability to adapt to light and heat depending on the season and individual needs significantly, directly, and sustainably reduces overall energy loads, especially for cooling the building. This technology replaces mechanical sun protection systems. Through the combination of innovative technologies, reused materials, and modular construction, a sustainable, functional, and aesthetically demanding solution was realized. The project demonstrates how existing buildings can be made fit for the future through circular approaches and provides an example of an architecture that conserves the environment and resources without compromising quality and innovation.
Readers interested in learning more about this project can find more information in the two books: Totalsanierung Müllerstrasse (Drittel Books) and Neues Zirkuläres Bauen (Park Books).
