Why does WELL advocate for blue-enriched daytime lighting?

• A. Because they have a greater circadian impact due to higher blue content and EML.
• B. Because they are cheaper to produce.
• C. Because they render colors more accurately.
• D. Because they make rooms feel cooler.

Answer: (A)

Blue-enriched daytime lighting is favored because the blue portion of the spectrum more effectively activates the circadian system. The melanopsin-containing cells in the eye respond strongest to blue light around 480 nm, so increasing blue content during the day raises the melanopic stimulus, often quantified as melanopic lux (EML) or a related circadian metric. This stronger circadian input promotes alertness, mood, and better alignment of the body clock with daytime activity. The other options miss the main driver: cost or color accuracy are not the primary reason WELL promotes blue-enriched daytime light, and the idea that it makes rooms feel cooler is just a perceptual byproduct, not a physiological goal.