The project of the Nasher Sculpture Center in Dallas consists of a two-acre sculpture garden and gallery building which opened to the public in October 2003. The brief was to create a home for one of the most significant collections of 20th Century Sculpture. The resulting two-storey gallery building is conceived upon the concept of a “museum without a roof”. It contains an auditorium, a restaurant and workshop facilities along with a wide gallery space. One of the driving concepts for the building was to maximise natural daylight in the principal internal galleries so that giving optimum viewing conditions for the artwork. This desire conflicts with the requirements to protect sensitive works from exposure to direct sunlight and with the need to control solar heat gain.
The roof concept was to have a high-performance glass roof over the galleries with a carpet of cast aluminium external shading elements floating above, filtering the sunlight and providing solar protection in as thin a build-up as possible, thus eliminating artificial illumination much of the time. The project went back to first principles to develop an innovative external shading sun screen solution together with the curved and tension supported roof structure.
The design team at Arup has worked closely with architect, Renzo Piano, to deliver this matrix of day light blockers. The result is an eye-catching roof composed of over half a million aluminium 'shells'. Each one weighs a mere 40 grams and is precisely cast at the correct angle to exclude the direct rays of the sun whilst maximising and precisely controlling daylight as the sun tracks across the Dallas sky. These elements grant a perfect microclimate whilst eliminating hard shadows across the sculptures in the gallery. For geometric accuracy, the sun's altitude and the critical solar angles are precisely calculated for the site throughout the year. This critical numerical configuration dictates the curvature of the shading shells and therefore, the design and effectiveness of the roof. Three-dimensional computer models were used for the development of the form allowing the integration of the complex solar data with the geometric models. Throughout the development all information was communicated through the exchange of 3D models. 3D modelling software produced sophisticated renderings of the shading, and prototyping was used to fully explore the geometry: full-scale, accurate physical prototypes can be produced directly from the 3D computer models allowing the direct production of aluminium prototypes through a process of sand-casting.