Office Building Holbeinstrasse

Two properties in Zurich's Seefeldquartier from 1961 and 1973 were repaired, converted and connected to form a new, efficient office building. Holbeinstrasse 30 was originally an office and business building, whereas number 22 had a purely commercial purpose. This meant that they had different floor heights, load-bearing structures and access systems. Meeting the specifications for access and earthquake safety meant retaining the concrete skeleton. This required an additional evacuation route and improved reinforcement for the buildings. The decision was made to replace the core of Holbeinstrasse 30 and install a new emergency staircase, which would also secure the long-term flexibility of the space distribution. This also made it possible to redesign the staircase and sanitary facilities, as well as efficiently arranging the shaft spaces for the building services. The same measures were also taken in Holbeinstrasse 22. From the outside, both buildings appear similar, owing to the radical conversions that were carried out simultaneously. The quality of the new façade can be seen in the way the different window formats differentiate the buildings. The smallest window format measures 0.6 x 2 m and the largest 3 x 4 m, with identical construction. What appears as a punctuated façade is, in fact, designed as a pre-fabricated element façade. The existing façade material found at Holbeinstrasse 22, a mixture of different-coloured stoneware mosaics, was used as a motif and was reinterpreted. Thermally separated aluminium profiles house the suspended glass panels and rear-ventilated, smooth, glass mosaic strips. Sun protection is provided in the form of delicate exterior blinds fitted in a protected intermediate space in the window design. Thanks to the use of heat exchangers, the rooms are cooled and heated using only water from the lake. The new building meets the Minergie standard.