## 4 Discussion
### Circadian Stimulus  
As illustrated in Figure 11, the circadian stimulus experienced by inhabitants is strongly influenced by the architectural design. This design should be adapted to daylight conditions to ensure sufficient circadian entrainment by providing an appropriate quantity and spectral quality of light. Based on the analysis of the nursery design, a static architectural approach that cannot optimize daylight utilization in interior spaces often results in inadequate illuminance levels under certain circumstances, thereby disrupting proper circadian rhythms.  
As detailed in Figure 4 and illustrated in Figure 11, two scenarios are analyzed for the nursery classrooms. The first scenario examines the peak of melatonin suppression, occurring at 11 a.m. local time (10 a.m. solar time), which corresponds to a circadian stimulus of 0.4. This value is approximately equivalent to an illuminance of 300 lx or higher, considering only daylight conditions. The second scenario focuses on the peak of melatonin secretion, observed at 2 p.m. local time (1 p.m. solar time), with a circadian stimulus value of 0.2, approximately equivalent to 100 lx or lower based on daylight spectra. This second scenario corresponds to the children's rest time. Both scenarios are discussed in relation to the architectural design and boundary conditions of the nursery.  
Given that the classrooms in the nursery are oriented toward the north--resulting in no direct solar incidence within the interior spaces, with most daylight originating from externally reflected components--optimal conditions for children's rest occur only on cloudy days near the winter solstice, when most of the room is adequately illuminated.  
Under clear-sky conditions during the same period, the area suitable for children's naps is limited to within 1.25 m from the back of the room, indicating suboptimal performance for rest time. Furthermore, when examining the peak of melatonin suppression (around 11 a.m. local time), the winter solstice fails to provide any zone capable of supporting adequate circadian entrainment.  
During the equinoxes (21 March and 21 September), the area of the classroom suitable for children's naps is confined to a zone far from the window, ranging between 1.25 and 2.00 m from the back of the room, depending on weather conditions. Consequently, most of the classroom does not provide adequate circadian entrainment during rest time, highlighting the need for architectural adaptations, such as slats or shading devices, to effectively reduce daylight. Furthermore, during the melatonin suppression period (at 11 a.m. local time, 10 a.m. solar time), it is not possible to achieve an illuminance level above 300 lx--except in the area near the window--necessitating reliance on the electric lighting system to stimulate children during their alert phase.  
During the summer solstice, under the scenario of children's rest, only the area farthest from the window--between 0.75 and 1.25 m from the back of the room--is suitable, regardless of weather conditions. This observation underscores the necessity of active shading systems, such as slats, blinds, or curtains, to optimize the functionality of the interior space during children's nap times. In the scenario of melatonin suppression (at 11 a.m. local time, 10 a.m. solar time), only the area near the window provides sufficient stimulation for children's circadian entrainment, particularly under overcast sky conditions, where the higher luminance of the cloud layer contrasts with the relatively lower luminance of a clear blue sky without direct solar incidence. Consequently, there is a strong dependence on the building's electric lighting system, which must deliver not only functional task lighting but also an appropriate circadian stimulus. This entails modifying both the luminous flux and spectral characteristics to support a healthy chronobiological rhythm.