When the Hikari Library opened, the drawings promised even daylight on every reading table, with no blinds and no glare. Six months later we went back to Annecy with twelve sensors to see if the building keeps that promise.

We logged light levels every ten minutes, from the winter solstice to the first heatwave, and asked librarians where readers actually sit.

What we measured

• Daylight on the tables: 300 to 750 lux, ten hours a day.

• Direct sun on the reading surfaces: under 2% of opening hours.

• Artificial lighting switched on before 4 pm: only in December.

The clerestories do the work we drew them for. The lamps are mostly there for the evening.

What we would change

The south reading room runs warmer than modelled in June. Deeper timber fins on two bays would have been enough.

These measurements now feed our early design studies, so the next library starts from real numbers rather than software defaults.