J.H. Keller AG, Zurich

The old-established business J.H. Keller AG Automobile has been based in the commercial district on Vulkanstrasse in Zurich Altstetten since the mid-1950s. Following the redesign in 2017 of spaces in the former warehouse to serve as studios, in 2020 a complete energy efficiency retrofit of the building envelope was planned. In renovating the facade, the goal is to preserve the original expression and character of the existing building.

The building consists of a high-rise block on the street and the hall behind it. The entire building envelope is replaced and, where necessary, restored to its original state. As the renovation of the high-rise building’s rooftop level would be unreasonably expensive it is replaced by a lightweight timber construction and glazed on all sides.

The roof-top floor of the three-storey hall is reformulated by means of a new roofing that connects roof and facade with each other. A black, weather-resistant EPDM rubber membrane covers the new substructure. Roof lights, several of which can be opened, provide the space below with daylight. The mechanical fixings of the taut facade membrane make a visual impression not unlike buttoned upholstery. Consequently, the new facade refers in two ways to the first motor cars that were sold here from the middle of the last century onwards: a look at the membrane recalls the upholstered car seats, while the material rubber evokes tyres.

New photovoltaic panels on the roof supply power. In addition, photovoltaics built into the parapet bands on the south facade of the high-rise (“building-integrated photovoltaics” BiPV) are also used to produce energy.