WELL Building Standard — Lighting Features Explained
How WELL's L01-L09 lighting features transform workplace wellness through circadian and visual comfort requirements.
Why WELL Matters for Lighting
The WELL Building Standard is the world's leading certification focused on human health and wellness in the built environment. Unlike LEED (which is primarily environmental/energy focused), WELL places occupant well-being at the center. WELL v2 includes a dedicated Light concept (L) with features L01 through L09. Lighting accounts for a significant portion of certification points and is one of the most impactful concepts for occupant satisfaction, productivity, and health. In the GCC, WELL certification is rapidly growing — particularly in premium office developments, healthcare facilities, and hospitality projects in Dubai, Abu Dhabi, Riyadh, and Doha.
WELL v2 Light Features Overview
| 0 | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| L01 | Light Exposure | Precondition | Required | Minimum workspace illuminance for visual tasks |
| L02 | Visual Lighting Design | Precondition | Required | Luminance ratios, surface brightness balance |
| L03 | Circadian Lighting Design | Optimization | 1-3 pts | Melanopic EML at the eye for circadian health |
| L04 | Glare Control | Optimization | 1-2 pts | Architectural and shading solutions for solar/electric glare |
| L05 | Enhanced Daylight Access | Optimization | 1-3 pts | Proximity to windows, daylight availability |
| L06 | Visual Balance | Optimization | 1 pt | Ceiling and wall illuminance balance |
| L07 | Electric Light Quality | Optimization | 1-2 pts | CRI/Rf, flicker, and color consistency |
| L08 | Occupant Lighting Control | Optimization | 1-2 pts | Individual dimming, CCT, and on/off control |
| L09 | Daylight Management | Optimization | 1 pt | Automated blinds and shading |
L03 — Circadian Lighting (Key Feature)
L03 is the most technically demanding and impactful lighting feature. It requires delivering sufficient melanopic light at the occupant's eye level during daytime hours. Melanopic Equivalent Daylight Illuminance (m-EDI) is the metric. It quantifies how effectively a light source stimulates the intrinsically photosensitive retinal ganglion cells (ipRGCs) that regulate circadian rhythms. Tier 1 (1 point): ≥150 equivalent melanopic lux (EML) at the eye, measured vertically at 1.2m, for at least 4 hours/day. With enhanced daylight (L05): ≥120 EML. Tier 2 (3 points): ≥240-275 EML at the eye. This typically requires either very high illuminance levels (700+ photopic lux at 4000K) or tunable white systems that provide higher CCT (5000-6500K) during morning/midday hours. Evening consideration: Spaces used after dark should provide ≤50 EML to avoid circadian disruption before sleep.
Achieving L03 in Practice
To hit 150 EML at the eye level with 4000K sources, you need approximately 350-400 photopic lux vertically at 1.2m height. At 3000K, you'd need ~600-700 lux — often impractical. Strategy: Use 4000K-5000K for general office lighting during work hours, with dimming to 2700K-3000K after 5pm. Tunable white luminaires are the most effective solution for both L03 and L08 (occupant control).
L07 — Electric Light Quality
L07 targets the quality of electric light sources: • Color Rendering: CRI Ra ≥ 90 for all regularly occupied spaces, OR TM-30 Rf ≥ 78 with Rg ≥ 100 (encouraging adoption of the modern TM-30 metric). • Flicker: ≤ 5% flicker (modulation depth) below 100Hz, and SVM (Short-term flicker Visibility Measure) ≤ 1.0 at all dimming levels. • Color Consistency: All luminaires within 2 SDCM (Standard Deviation of Color Matching) for visual uniformity. These requirements eliminate cheap drivers that cause visible flicker and ensure color consistency that most occupants notice subconsciously but dramatically affects comfort.