WELL and Lighting

WELL is the one that surprises lighting people, because it asks for the opposite of what the energy code asks for. The energy code wants less light for fewer watts. WELL wants enough light of the right spectrum, at the right time of day, at the eye rather than at the desk, to support the occupant's circadian system.

Those two requirements pull against each other, and reconciling them is a genuine design problem rather than a paperwork exercise. It is also why WELL projects tend to need the controls conversation early.

How WELL is scored

• WELL v2 is the current standard, currently the Q2 2025 edition. WELL v1 is legacy.
• Preconditions are mandatory for any level of certification and earn no points. Optimizations are the scored items.
• Certification levels: Bronze at 40 points, Silver at 50, Gold at 60, Platinum at 80.
• There is a minimum per concept as the level rises: none for Bronze, 1 point for Silver, 2 for Gold, 3 for Platinum. So a Platinum project cannot simply ignore Light and make the points up elsewhere.
• Each concept is capped at 12 points, with 100 available across the ten concepts and 10 more for Innovation.

The Light concept

Light runs from L01 to L09. Two are preconditions, the rest are optimizations.

• L01 Light Exposure — precondition. Deliver light through one of four routes: daylight simulation, interior layout, building envelope, or meeting the first circadian tier electrically. The daylight route is now spatial daylight autonomy of 150 lux for 50 percent of hours across at least 30 percent of regularly occupied area, changed to align with IES LM-83-23.
• L02 Visual Lighting Design — precondition. Meet illuminance targets from a recognized standard, the IES Lighting Library, EN 12464, ISO 8995-1 or the CIBSE code among them, or use WELL's own light level table where the eligibility conditions are met.
• L03 Circadian Lighting Design — optimization. The centrepiece, and the one that changes the design.
• L04 Electric Light Glare Control — optimization.
• L05 Daylight Design Strategies and L06 Daylight Simulation — optimizations.
• L07 Visual Balance — optimization.
• L08 Electric Light Quality — optimization, covering color rendering and flicker.
• L09 Occupant Lighting Control — optimization.

Circadian lighting, which is the requirement that changes everything

This is where WELL departs from every other standard a lighting rep deals with. The metric is not lux on the desk. It is melanopic equivalent daylight illuminance, m-EDI, measured on a vertical plane at eye level, roughly four feet above the floor, facing the direction of gaze — because what matters is the light reaching the eye, not the light landing on the work surface.

WELL previously used equivalent melanopic lux and has moved to m-EDI. If a consultant hands you a target in EML, check which metric and which edition they are working from.

• Two tiers. Roughly 136 m-EDI for the lower tier and 250 m-EDI for the higher one. The higher figure is not arbitrary: an international expert consensus published in 2022 independently recommended at least 250 m-EDI at the eye during the day, and WELL's upper tier sits there.
• For at least four hours a day, in a window beginning by noon.
• Where enhanced daylight is achieved through the daylight features, the electric lighting thresholds drop, which is the standard rewarding you for using the sun.
• Dwelling units and guest rooms carry the same thresholds, must be dimmable, and where automated must dim down after 8pm.
• Verification is done at night, on electric light only, so daylight cannot flatter the result, with the median of samples required to meet the threshold.

The other numbers a specifier needs

• Glare, L04. Unified glare rating of 19 or less, or luminaire luminance of no more than 6,000 candela per square metre between 45 and 90 degrees from nadir, or no light emitted above horizontal. Note that this now lines up almost exactly with LEED v5's quality electric lighting path, which uses the same two numbers. One luminaire specification can satisfy both standards, which is a genuinely useful thing to know on a dual-certification project.
• Color rendering, L08 Part 1. In occupiable non-circulation areas, CRI of 90 or above, or CRI 80 or above with R9 of at least 50, or the TM-30 equivalent. Circulation areas are less demanding. WELL has been aligning this with the newest TM-30 revision, so confirm the current wording.
• Flicker, L08 Part 2. Luminaires must meet one of a set of low-flicker criteria, which include qualifying as reduced flicker operation under California Title 24. Flicker is the requirement most likely to be met by accident or missed by accident, because it is invisible on a cut sheet and usually not invisible on a phone camera.
• Occupant control, L09. Giving people control over their own light, which overlaps with LEED's interior lighting thinking and with plain good practice.

LEED and WELL together, honestly

They are not the same exercise and it is worth being clear about that with a client who says they want both.

LEED asks whether the building is efficient and low-impact. Lighting reaches it mostly through the energy model, plus specific credits for glare, color quality, daylight and light pollution. WELL asks whether the building is good for the people in it. Lighting is a whole concept of its own, and the flagship requirement actively wants more light.

Where they agree, use it: the glare numbers are effectively the same, both care about color rendering, and both reward daylight. Where they disagree, the disagreement is real and somebody has to decide. A project chasing WELL Platinum and an aggressive LEED energy score has set itself a genuine engineering problem in the lighting, and the earlier that is on the table the cheaper it is to solve.

Common questions

Related: LEED and lighting · Florida energy code lighting · ASHRAE 90.1 for lighting · Healthcare lighting · Lighting controls guide