The high power projectors installed above the glass 'bolla' housing the rainforest exhibit provide the life support lighting that supplements the daylight that enters through the skylights in the concrete structure of the outer, living roof.

Fitted in the space between the concrete roof and the 90ft diameter glass dome, they illuminate through the glass onto the rainforest canopy, with its spiralling path that leads visitors through the close-up rainforest experience.

Arup specified 140 one and two kilowatt 003 series high power projectors from Sill - designed for the Osram HQI-TS lamp - as the light source has a high Photosynthetic Active Radiation efficiency, making them the closest to daylight.

The high wattage fixtures have been installed outside the glass dome surrounding the Living Forest, keeping the temperature of the tree canopies below 100°F to provide a comfortable temperature for the butterflies in the exhibit.

The US$488m (£302.2m) California Academy of Sciences is the result of a seven-year collaboration between Arup and the architects Renzo Piano Building Workshop and Stantec Architecture.

The facility, which features a wide range of green building technologies and strategies, is reported to be the world's greenest museum.