Nantes, in western France, is celebrated for the quality of its soft Atlantic daylight, and light is the major theme of Stanton Williams’ renovation and extension of the city’s art museum. The competition-winning project expands the institution from its original home in a late-nineteenth-century Beaux Arts ‘palais’, adding an extension known as the Cube (linked below ground via a new basement, and above via a high-level bridge), and a street-facing archive-building. A former seventeenth-century chapel, which now houses a work by Bill Viola, is also drawn into the ensemble, which Stanton Williams has conceived as an architectural promenade around an outdoor sculpture court.
Though is it not readily apparent from the vaulted limestone entrance hall and grand staircase, the Palais is an early example of steel frame construction, and the pitched steel-framed rooflights over its upper-level galleries and central courtyard, or ‘Patio’, are a distinctive feature. Stanton Williams has renovated these to preserve their outward appearance while moderating the quality of daylight admitted through the addition of internal layers. Single glazing in the steel frames was replaced, and additional double-glazed units were installed horizontally at the base of the rooflights to improve thermal performance. Below them, translucent stretched fabric panels screen the glazing from view internally. Stanton Williams also worked with services engineer Max Fordham to neatly integrate air and smoke extraction vents around the edges of the fabric panels, with plant concealed out of sight within the volume of the rooflights.
Electric lighting is also installed with the void above the fabric ceiling. This can be used to supplement the daylight reaching the galleries, but the architects were keen to ensure that changing light levels and shadows cast by the steel structure gave visitors a “poetic” sense of connection to the sky above.
Filtered daylight also animates the interior of the four-story ‘Cube’ extension, where a curtain wall of translucent marble screens a stair on the south facade. Comprising 6mm-thick sheets of veined stone bonded into double-glazed units, it refers both to the mineral facades of the Palais, and to the use of alabaster to admit daylight into Medieval churches while protecting precious artworks.
In both the design of the curtain wall and the environmental strategy developed for the galleries, the architects were obliged to challenge local conventions and building regulations. “The approach to environmental control in French museums dates from the 1960s”, says Stanton Williams director Patrick Richard. “We proposed a more contemporary, passive approach that allows slow temperature changes. That means galleries do not have to be like fridges, with a lot of plant overhead killing any possibility of downlight”.