The lack of natural light in a tiny Parisian studio apartment prompted Betillon / Dorval-Bory to rethink the use of interior artificial lighting.

Through researching the colour rendering index (CRI) – which describes light’s ability to reflect the accurate colour of a surface – Raphaël Bétillon and Nicolas Dorval-Bory adopted a Philippe Rahm-like approach to the division of space. ‘The idea was to explore the qualities of various light sources from an objective and scientific point of view,’ says Dorval-Bory, ‘before creating architecture that considers – and uses – these spatial qualities.’

At opposite ends of the spectrum lie low-pressure sodium lamps (LPS) and high-CRI fluorescent lighting. The former – popular due to their high efficiency – have poor colour rendering and are usually used for street illumination, whereas the latter provide good task lighting.

For Spectral Apartment, Bétillon and Dorval-Bory began by dividing the space according to its various lighting requirements and forming a hierarchy of colour rendering; distinguishing colours is more important in the kitchen, for example, than in the bedroom and bathroom. The room is then divided by high- and low-CRI lighting. Holding two separate light sources, a simple 2-m-high wall generates the composition. On one side the lamps are over 90 CRI (100 is the maximum, which is the equivalent of daylight) while warm LPS lamps with a CRI rating of zero are fitted on the reverse.

Both sources have separate switches, which creates changeable lighting patterns and leads to different uses of particular areas in the apartment. The designers say that the space’s otherwise neutral palette annihilates architectural expression or narrative, leaving only the logic of composition generated by light.