The Komische Oper Expansion condenses its essential functions into a dynamic ‘Nucleus:’ the two rehearsal stages, the orchestra rehearsal, and the suite of practice rooms straddle a central ‘Circulation Hub’ containing passenger and scene elevators, stairs, and lounges for the fluid movement of performers, scenery, instruments, and equipment. This compact organization renders the Nucleus a highly efficient rehearsal node and—due to the variable raked floor machinery in the rehearsal stages—a lively public performance venue, able to also host private functions for increased economic productivity.

The Nucleus’ Circulation Hub connects performers and technicians—as well as rehearsal and other support spaces—directly to the existing Komische Oper’s main stage and orchestra pit. The larger rehearsal stage is adjacent to the side stage entrance, allowing set configurations to be tested and transported without disrupting other functions. The new orchestra rehearsal and instrument storage are aligned with the orchestra pit, ensuring timely turn-over from preshow uses. In addition to maximizing connectivity with the existing Komische Oper, the Nucleus’ compactness preserves the required loading and egress alleys while maintaining the critical 20-meter-wide footprint of the rehearsal stages.

Performer and staff access to the Komische Oper Expansion is off Glinkastraße to retain primacy of the Komische Oper’s distinct entrance on Behrenstraße, both as the public access point for audiences and as a cultural landmark in Mitte. The existing performer entrance to Komische Oper in the rear courtyard is improved with a new security vestibule adjacent to—and with security oversight of—the Expansions’ scene dock. The Nucleus’ compactness also enables urban activators to cap its ends. On Behrenstraße, the three stacked floors of the café provide views both out to the city and into the larger rehearsal stage.

A new public plaza—the ‘Urban Room’—in front of the café supports outdoor dining and can serve as an exterior venue for performances, exhibitions, markets, fashion shows, or cinema. On Unter den Linden, the new box office, shop, and restaurant increase the Komische Oper’s visibility on this popular thoroughfare. Like the café, the restaurant—with its own, dedicated entrance for independent operation—allows guests to watch the rehearsal activities in the smaller rehearsal stage. As these public uses will draw in foot traffic, they also create new patron engagement with Komische Oper’s programming and support non-performance revenue streams.

When the rehearsal stages serve as public performance spaces, patrons access these venues from the entrances of the café and restaurant such that clear demarcation between public and private functions is maintained; portions of the café and restaurant become the venues’ lobby and bar spaces. The Expansion lines up strategically with the back of Komische Oper’s entry block to preserve the important sightlines to its historic entrance, and maintains the loading alley as a passageway under the extension.

The offices, instrument storage, and mechanical spaces are organized in long bars above and below the Nucleus and the new urban amenities, stretching to the site’s full 110 m. The office floors feature double-story courtyards that introduce daylight and fresh air into the work spaces. They can be used year-round thanks to deployable EFTE pillows. The office floors create a 20-meter-long cantilever on Behrenstraße that defines the Urban Room. At almost 15 m high, the cantilever frames views to the Komische Oper from the corner of Glinkastraße and Behrenstraße, further enhancing the respectful symbiosis between the two buildings.

A similar 10-meter-long cantilever (creating the glass-enclosed box office below) on Unter den Linden extends the Opera Support Building’s covered public walkway. The Expansion’s double-skin façade with its integrated stone louvers (matching the white Cottaer Sandstone to be reinstalled on the existing Komische Oper) is one of the building’s most notable features, visually and sustainably. The 3 m to 4.2 m tall arced louvers rotate 180 degrees to track the sun, but also give performers the options to 1) expose their work—as desired—to passers-by, 2) benefit from rehearsing in full daylight, with minimized brightness and glare, or 3) create full blackout environments.

The façade’s ever-changing nature gives the building its subtle yet dynamic identity. Each facade’s two glazing layers, the naturally-ventilated cavity between them, and their enclosed, stone sun/glare-control louvers, combine to significantly reduce the building’s mechanical and electrical loads. The double-skin/air cavity mitigates the fluctuations of external temperatures and creates a chimney stack effect which naturally ventilates the cavity. When the stone louvers are rotated perpendicular to the sun, daylight reaches deep into the building, reducing electrical loads and warming up the structure’s floors and walls for passive heating.

The façade’s external glazing layer is comprised of heat-curved, laminated, uncoated low-iron glass panels that are pre-bonded to extruded aluminum interlocking cassettes, affixed to top-hung steel “T” profiles providing a minimal appearance. The internal glazing layer is composed of double-glazed, heat-curved, low-iron safety glass units with a triple-silver low-E coating on surface 3; it is installed similarly to the external laminated panel with a pre-glazed aluminum assembly and steel “T” profile.

The aggregate window-wall U-value is 0.70 W/m2K with a high SHGC of 0.20 for solar heat gains in winter. The glass façade system plays a significant role in the Expansion’s acoustic performance: • the double façade isolates the rehearsal stages, orchestra rehearsal, practice rooms, public programs, and offices from street noise; the stone louvers allow the rooms to reveal themselves and the activity within them without impacting their acoustic integrity; the mass and integral damping of the 20 mm glass inner lite in the insulating glass system contribute acoustic warmth and mitigate brightness often associated with glass when it is used as an acoustic finish; and the curved glass provides acoustic diffusion and—working together with the technical catwalks in the rehearsal stages—acoustic support for the performers.

Spanning each of the office’s five courtyards is an operable frame mounted with ETFE pillows. The frame is attached to tracks that allow the operable roof to slide open making the courtyards a year-round amenity for staff. When closed, the frame is designed as a fully gasketed, thermally broken system and acts as the courtyard’s thermal line. The air-inflated panels improve U-Value thermal performance and, through printed patterns, can reduce the SHGC as required. The entire façade is suspended from the roof to protect it from variable slab movements and minimize horizontal joints along the glazed surface.

At the corner of Behrenstraße and Glinkastraße, the Urban Room under the Expansion’s cantilever adds a dynamic public plaza to the Komische Oper complex and Mitte. This ever-changing public square serves both as an outdoor seating area for the café and as an event space for exhibitions, performances, markets, fashions shows, or cinema. In addition to attracting new patrons, the versatility of this space offers the Komische Oper a different source of revenue through institutional partnerships, further ensuring its social and economic sustainability.

Three closed concrete cores at the center and at both ends of the Expansion compose its primary structural system. Besides functioning as the main vertical support elements, the rigid cores also absorb lateral movement, induced primarily by wind loading. All generic, non-isolated floor slabs are supported by a combination of the cores and concrete columns; except for the conventional concrete slab on the ground floor, they are Holorib to achieve high efficiency and weight reduction. At the top two floors—the offices—four parallel, double-height trusses span the building’s full length, a continuous beam working with the concrete cores to form the 20-meter-long cantilever hovering above the Urban Room and the 10-meter-long cantilever over the box office.

Floating above the generic slabs and below the top floor trusses, all the rehearsal spaces employ a box-in-box concept, providing optimal sound and vibration isolation amongst the rooms and from the superstructure. The rehearsal stages and orchestra rehearsal are constructed as independent boxes resting on isolators and attached laterally to the primary superstructure using acoustic wall ties. The larger rehearsal stage and orchestra rehearsal boxes are built using various combinations of conventional and prestressed precast concrete floor/ceiling slabs, precast walls, and steel trusses, while the small rehearsal stage box is composed of a precast concrete slab and plasterboard walls/ceilings.

By contrast, the practice room boxes—composed of wood floors and plasterboard walls/ceilings—are resiliently supported on a conventional concrete slab suspended by hangers from the office trusses. The Expansion adopts several sustainable strategies, including a naturally-ventilated façade, optimized building systems (displacement ventilation; plenum air distribution; high-efficiency, sensible, and latent heat recovery units and low-pressure air ducting; radiant thermal systems; geothermal ground source system), photovoltaic modules, green roof, and open space.

Natural ventilation at the office levels is provided via the passively tempered courtyards, which are thermally closed in winter with triple layer ETFE pillows that can be opened in the intermediate and summer seasons. This creates semi-open planted buffer spaces, ranging from a minimum annual temperature of 12°C in winter to shaded ambient temperatures in summer for full use as breakout and recreational spaces. The courtyard facades are single glazed for optimal daylight quality and natural ventilation for the offices.

A textile shading system below the ETFE pillows helps control daylight, glare, and temperature.