La Villette Roof and Heliomirrors

Designed to naturally light the main entrance area of the museum, this 2000m2 roof has been specially designed following a conscious geometrical hierarchy to transform the awkward dimensions of the existing building’s main structure.

A structure, “the spider”, is suspended from the existing roof beams and by means of “flying columns” and two annular beams supports two 28m diameter rotating domes, equipped with “robotic mirrors” which control the quantity and quality (direction) of sunlight penetrating to the space below. Between the domes and the outer rectangular edge of the roof is tensioned a double-skinned fabric roof (PTFE) with white insulation (Fibair) and a clear fibre reinforced Tedlar® film vapour barrier. This was one of the earliest thermally insulated translucent tension membrane roofs in the world.

The two large rotating domes that follow the daily movement of the sun on a horizontal plane are equipped with lightweight reflecting mirrors. These are programmed to rotate automatically in the vertical plane, and translate in the horizontal plane in conjunction with the dome’s rotation to provide the entrance hall below with controlled sunlight. The functions that are capable of being executed are:
– Parallel light perpendicular to the floor,
– Focusing and diverging light at specified moments, or under manual control
– Parallel light from an artificial source at night
– Focusing of above,
– Blackout
– Providing diffused sunlight by using the reverse side of the mirrors,
– Parking to allow maximum skylight when sunrays are not available.
The whole system is computer controlled remotely for educational purposes and will immediately relocate itself for automatic function. With the museum’s change of director, the system was later removed in the 1990s.