Circadian Architecture
This pattern is shaped by
Problem
Artificial lighting at constant color temperature and constant intensity disrupts the body's circadian rhythm — the 24-hour biological clock that regulates sleep, hormone production, metabolism, and mood. When indoor light never changes, the body loses its sense of time.
Evidence and Discussion
The circadian system responds primarily to light color temperature and intensity: cool, bright light (5000K+) in the morning suppresses melatonin and promotes alertness; warm, dim light (2700K or less) in the evening allows melatonin production and prepares for sleep. Buildings that provide only one light quality — the standard 4000K fluorescent — fight the body's natural rhythm all day.
Therefore
design interior lighting as a circadian system — cool and bright (5000K, 500+ lux) in morning-occupied spaces (kitchen, workspace), transitioning to warm and dim (2700K, 100 lux or less) in evening-occupied spaces (living room, bedroom). Use tunable white LED fixtures where electric light is the primary source. Maximize daylight access — the best circadian lighting is the sky itself. The building should help the body know what time it is.