Carnal Hall at Le Rosey

Located by Lake Geneva in the provincial town of Rolle, the renowned Swiss international boarding school known as Le Rosey is entered along an allée of trees that date back centuries. This traditional entrance frames the problematic of integrating a new arts center into an existing campus vernacular without imitating the past or creating a disturbing break with its most revered structures. How can architecture establish a complementary relationship or dialogue between tradition and modernity?

The program for a new performing arts facility for one of Switzerland’s most esteemed educational institutions includes an 900-seat concert hall, black-box theater, several conference rooms, rehearsal and practice spaces, a library and learning center, a restaurant, café, student lounge, and other amenities. Carnal Hall will be the first major new building constructed on the campus, which is situated equidistant from Geneva and Lausanne, since the original facilities were built in the late nineteenth century.

Despite a tight budget, the objectives for the concert hall are ambitious: it is intended to provide a world-class auditorium that is equally capable of serving the international student community and welcoming the most prestigious orchestras in the world.

The new building needed to infuse the campus with a contemporary architectural image while nevertheless maintaining the qualities that have made the school a revered institution. How can it remain sufficiently abstract to avoid being caught in a formal battle with the existing surroundings? A further question pertains to the program requirements—a concert hall, music conservatory, art studios, learning center, black-box theater, library, offices, guest rooms, and so on. Should you scatter them around the site or will you find a common denominator among them?

We felt the various aspects of the program should intersect in one single place, and proposed a low-lying, flat dome—a metal envelope that seems to emerge from out of the landscape, shining by day and reflecting ambient campus light by night.

From the air, the dome appears as a distinctive object, but at ground level its curvature fits into the landscape. In plan, its shape recalls a rose or rosette—a fitting allusion for Le Rosey.

The aim of the distribution of activities is clarity and legibility. On arrival, the visitor encounters the main concert or performance hall, the conference rooms, and the black-box theater. To the left are ground-floor educational spaces. To the right is access to the learning center and the restaurant, which also has an independent entrance located near its terrace. A series of side openings articulates the periphery. A forecourt to the main entrance and the concert hall is located along the west facade.

Located at the center of a semi-spherical void, a complex solid object contains four rectangular voids: the concert hall, black-box theater, music rehearsal room, and library. The void between the dome and this central object is a dynamic space of movement and fluent exchange. In contrast, the four voids inside the central object are intentionally static.

The architectural concept articulates the building into three parts: first, the dome with its steel structure and stainless-steel outer envelope; second, the base with two carefully detailed concrete levels accommodating art studios, practice rooms, learning center, backstage, and all offices; and third, the wooden core containing the concert hall, black-box theater, music rehearsal room, and library.

Materials played a role in conceptualizing the project: the most important part of the program, the concert hall, fits under the dome and is clad inside and outside in wood to contrast with the metal outer envelope. This double-envelope strategy also helps isolate the concert hall acoustically, so as to mitigate noise from nearby rail lines. Each material is expressed and detailed specifically to reinforce the concept of the wooden box under a steel dome. Glass is present only as a vertical separation between exterior and interior or public and private and (in alternatively transparent or reflective forms) as a screen.

Carnal Hall features the first philharmonic concert hall of this size which repurposes modest, utilitarian Oriented Strand Board (OSB) wood—typically used on construction sites— to achieve world-class acoustics on budget. Wood finishes articulate three main objects enclosed under the roof dome—the concert hall, music rehearsal room, and library—and provide needed acoustic treatment for the concert hall, rehearsal room and large public spaces. OSB was chosen for a number of reasons. Architecturally, the use of a lightened OSB material put a contemporary twist on an oft-used material, while unifying several architectural objects contained under the roof dome. Acoustically, OSB is a new and exciting material choice for a concert hall with surface texture needed to create a warm musical sound reminiscent of rooms in traditional theaters. The OSB was acoustically tested and treated to enhance the material’s fine surface texture while minimizing the OSB’s porosity. Tight budget constraints proved that a non-toxic, treated OSB material for wood surfaces was not only an ecological but economical choice. Wood finishes were expertly installed by Pascal Schwab to meet stringent architectural and acoustic requirements.

Wood surfaces facing onto the public spaces are offset against the gray, concrete floors and the white of the acoustic ceiling and steel structure. Glass walls complement the wood and concrete interior surfaces. Large glass surfaces integrated into each end of the concert hall bring in natural light and views for spectators and musicians alike. Glass facades inside the building activate circulation routes. The exterior entrance façade continues as an interior façade, articulating the edge of the architectural stair ramps that lead to the upper level while highlighting movement through the various open public spaces of the building. Full- height interior facades transition to glass handrails on the upper level, again maximizing the sense of movement throughout the building while minimizing the number of materials used.

All of the programs are organized under an arching stainless steel dome that hovers over the Le Rosey campus, covered by approximately 5,000 panels over a roof area of 4,500 m2 and a diameter of 80 meters. The stainless steel is conceptually important, differentiating Carnal Hall from Le Rosey’s existing campus while unifying the diverse programs of the building. Functionally, cutouts in the dome define shaded overhangs for perimeter rooms and accessible balconies. During the day, the low-lying dome reflects the sloping grounds and rolling clouds of the school’s bucolic context. The 57-ton steel structure for the dome ties back to concrete walls and columns that are distinct from the separate, acoustically- isolated “inner” concrete structure to which concert hall walls and finishes are attached.

In the case of Carnal Hall, architectural and acoustic considerations were inextricably linked at every phase of design. Bernard Tschumi Architects worked with a cross- disciplinary team of engineers at Arup through design development, including the acoustician Alban Bassuet. Together, architectural and acoustic concepts were tested: from the overall shape of the hall to the integration of glazed surfaces and a rhythm of wood joists all designed to create an enveloping sound for the audience.

The proportions and shallow rake of the room create reflections from the sides and back of the hall generating an intimate sound in all seats: the rectangular hall shape provides needed reflections for the lower level of the room; the rectangular “halos” situated along the upper edges of the hall generate reflections for the balcony level. Acoustical focusing of sound from the concave ceiling of the hall was counteracted by the addition of orchestra reflectors, ensuring that music generated by small student ensembles and large, renowned orchestras is reflected to the walls and the audience. The hall has also been adapted for film projection, lectures and amplified music.

Concert hall wall shaping requirements were generated by acousticians to diffuse and reflect sound throughout the hall. Large and small joists affixed to the wood surfaces were dimensioned and organized to achieve the appropriate acoustic effect using “3D corners” (in which the wall intersects with 2 joists), creating three surfaces perpendicular to each other that reflect sound back to where it initiates. These joists are angled and not perpendicular to the floor creating a perspectival effect so that the stage appears sloped and not flat (in contrast to Baroque theaters that actually had sloped stages). In the small rehearsal room, angled wood surfaces prevent excessive loudness, breaking up sound for both practices and performances. The archi-acoustic motif of angled joists was inverted for the concert hall wall facing onto the grand entrance foyer where joist patterns are expressed as recessed joints located between triangular OSB panels.

The visible underside of the roof sandwich panels are perforated acoustic panels, which when paired with vertical wood surfaces and carpet infills, fosters a lively, cross- disciplinary environment in the large public spaces where students and teachers gather, work and relax. All upper-level music practice and meeting rooms have a separate ceiling enclosing the rooms under the roof and ensuring sound isolation from the large public spaces.