Office tower, Amsterdam

The recently completed 21-storey UNStudio Tower forms part of the Mahler 4 urban complex, a cluster of six buildings located in the heart of the South Axis in Amsterdam. The South Axis connects Schiphol Airport to the major business areas of Amsterdam South. The Mahler 4 complex houses 38,000 m² of residential spaces, 162,000 m² of office space and 30,000 m² of street level retail, cafes, restaurants and a sports centre. The six towers in the complex range in height from 85 to 100 meters, with each building carrying the name of its designing firm. At a height of 82.5 meters, the UNStudio Tower contains twenty floors of office space and a ground floor with mezzanine.

The facade of the UNStudio Tower plays with the juxtaposition of a horizontal and vertical articulation, conceptually relating to the principles upon which the moiré effect is based. The horizontal articulation is provided by white aluminium bands which wrap the tower, whilst their varying size, depth and transparency ensure the correct balance of sun screening and light penetration to the interiors on all levels of the building.

Vertical accents are formed by voids, recessed into each face of the building and spanning differing numbers of floors. These voids serve to create an inside-outside relationship, which extends the facade envelope and turns the surface of the tower into an active medium with a profound effect on the quality of the interior user space. Custom coloured glass panes are incorporated into the vertical voids, offering different identities and light qualities to the communal spaces which surround each void in the interior. These voids further facilitate daylight penetration deep into the extensive 40×40 metre floors.

Voids are often placed at the centre of a building, but here they are placed at the perimeters. This has three major advantages: the voids are easily transformed into (internal and external) balconies; the usable floor space is larger and can be planned more flexibly; the depth of the floors further ensures a high facade to gross floor ratio, whilst the building as whole has a 90% net to gross ratio. The quality of the void spaces is affected by their location. Instead of public circulation space, these voids offer space for small meetings or personal reflection.

Whereas conventional office buildings with their strict separation of inside and outside can be experienced as somewhat confining by contemporary office workers, the transparency of the primarily glass facade, in combination with the vertical voids, offers the user a gradient experience of the inside-outside condition, as well as the perception of an open and light interior. The outdoor spaces, which are incorporated into the recessed voids in the form of roofed balconies, allow for transition from inside to outside during free time or breaks. In addition, a roof terrace with a sky view towards Amsterdam's Old South can be accessed for larger outdoor gatherings.

Flexibility with respect to future change of use with an ambition towards minimum alteration was paramount in the design of the UNStudio Tower. Extensive research was carried out in collaboration with the client in order to determine where maximum flexibility could be incorporated into the design from the outset. As a result, the floor plans of the UNStudio Tower incorporate the potential for future residential use with no structural alteration required.

The vertical voids recessed into the facade of the building also offer the potential to be transformed into individual balconies on each floor for residential use in the future. The facade design further incorporates a system whereby the glass panes can be replaced with minimum intervention should a change of use become desirable.