Support circadian health through interventions using electric lighting.
Since ipRGCs are located in the retina of the eye, the light levels entering the eye of the occupant must be considered. While developing lighting design for circadian impact, the light levels must be achieved on the vertical plane, at the eye level of the occupant to simulate the light entering the eye of the user. It is also important to consider the duration of exposure to light as well as the timing of exposure. Stimulating the circadian system at night through exposure to bright light can negatively impact sleep quality.
Indoor light levels can have a larger impact on people than seasonal changes in daylight hours. Supporting the circadian health of users through electric lighting interventions can help maintain a healthy circadian system and improve sleep quality, mood and cognitive functions.
Lighting for the Circadian System (Max: 3 points)
Electric lighting is used to achieve light levels shown in the table below as measured on the vertical plane at eye level of the occupant. The light levels are achieved at least between the hours of 9 a.m. and 1 p.m. and may be lowered after 8 p.m. at night:
The project meets the following requirements in regularly occupied spaces:
Option 1 Option 2 Points At least 150 EML [136 melanopic equivalent daylight D65] OR The project achieves at least 120 EML [109 melanopic equivalent daylight D65] with electric light and at least 2 points in Feature L05: Enhanced Daylight Access. 1 At least 240 EML [218 melanopic equivalent daylight D65] OR
The project achieves at least 180 EML [163 melanopic equivalent daylight D65] with electric light and at least 2 points in Feature L05: Enhanced Daylight Access.
Note: For workstations, the light levels may be achieved at 45 cm [18 in] above the work plane.
For spaces without workstations, light levels may be achieved at a height of 140 cm [55 in]. See the Performance Verification Guidebook for more details. Projects pursuing WELL Core or that have spaces that do not have furniture installed prior to Performance Verification may submit an annotated architectural plan indicating furniture layout for documentation review.
Note that light levels are achieved on the vertical plane at eye level to simulate the light entering the eye of the occupant.
Appendix L1 shows how to calculate the EML of individual light sources.
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