Light: Daylight, Electric Lighting, and Circadian Considerations
What the exam tests
Light questions ask you to separate daylight availability, glare, electric-light quality, and circadian stimulus. You need to know which metric answers which question.
Core rules
- Daylight is evaluated spatially, not by a single point. WELL uses annual simulation metrics such as spatial daylight autonomy and annual sunlight exposure; a daylight factor alone does not show whether desks are daylit or glare-prone.
- Glare control is separate from daylight quantity: shades, light shelves, and orientation matter.
- Electric lighting quality includes illuminance, color rendering, color temperature, flicker, and glare. Good task illuminance can still be poor lighting if glare or flicker is high.
- Circadian design considers light at the eye, timing, spectrum, and duration. Bright light at night can disrupt sleep; daytime light exposure supports alertness.
Worked example
A floor plan shows 80% of workstations within 5 m of a window, so the designer claims daylight credit. The simulation shows sDA of only 35% because deep partitions block light. The reasoning: proximity to a window is not daylight autonomy. The fix is to lower partitions, add a light shelf, or increase window height, then rerun the annual simulation.
Traps
Using a single lux reading at noon as daylight proof. Confusing illuminance on the desk with light at the eye. Ignoring glare when reporting high daylight. Treating correlated color temperature as a circadian metric by itself.