How the WELL Light Concept Changed from v1 to v2

The WELL Light Concept logo

The second version of the WELL Building Standard is here, bringing myriad improvements. IWBI, the organization behind the standard, has more clearly delineated what a healthy building must be and what a healthy building could be.

Light is one of ten concepts covered by WELL, and v2 brings changes that make the standard more robust and easy to understand. For lighting designers, manufacturers, and other professionals, the following are significant changes you should be aware of.

Simpler naming and organization

One immediately noticeable difference is the consolidation, simpler naming, and simpler numbering of features. For example, v1 feature 55 (electric light glare control) and feature 56 (solar glare control) have been reorganized into a single feature—L04 Glare Control.

The Light Concept has been reorganized into eight clearly-labeled features

It is now obvious at a glance which features are preconditions (marked by P) and which are designated for higher levels of certification (marked by a maximum point value). Point values are weighted based on positive potential for impact.

A table now clearly defines luminaire shielding angles in L04 Glare Control, Part 2c

Within features, information is also organized more clearly. For example, tables replace lists and space types are cleanly delineated. The maximum points available for each part of an optimization are marked next to the title.

Feature parts now clearly separate types of spaces and specify the maximum optimization points available

Daylight and circadian lighting at the forefront

Aspects of v1 features 54 (circadian lighting design), 61 (right to light), and 62 (daylight modeling) have been integrated into part 1 of the new L01 Light Exposure and Education feature.

L01 is a precondition, which means that daylighting and/or circadian lighting design must be integrated into a WELL v2 project. In WELL v1, many daylighting considerations were optimizations.

L03 Circadian Lighting Design can earn up to three points (on top of L01) as an optimization. While circadian lighting design is no longer a precondition, it is complementary with L01 and thus an attractive pathway for many projects.

Circadian lighting requirements are a lot more straightforward in L03 than in the old feature 54. Between 9 AM and 1 PM, regularly occupied spaces must meet equivalent melanopic lux targets. L03 also clearly states that lighting may be dimmed after 8 PM.

EML targets are much more straightforward in WELL v2 feature L03 Circadian Lighting Design

For projects looking for additional optimization points, L05 Enhanced Daylight Access outlines strategies for maximizing occupant daylight exposure. L05 part 1 incorporates aspects of v1 features 61 and 63 governing window size, transmission, and distance to workstations for 1 point.

L05 part 2 is an improvement over v1 feature 62 (daylight modeling), providing an extra point for achieving sDA 300,50% in >75% of regularly occupied space:

L05 Enhanced Daylight Access provides an additional point for achieving sDA 300,50% in >75% of space

L05 part 3 introduces new optimizations defining the type of view outside the building, such as distance to roadways and access to sky views. If one of the requirements is met, an additional point is earned.

Flicker, CRI, and TM-30

WELL v2 improves upon v1 with L07 Electric Lighting Quality. Electric lighting for all spaces (except circulation areas) can gain an optimization point if the color meets a CRI, R9, or TM-30-18 target. Circulation areas must meet targets that are less strict.

L07 Electric Lighting Quality provides more options for evaluating color rendering performance

It is interesting to note that the standard calls out not only the fidelity index (Rf) and gamut index (Rg) values for TM-30-18, but also the red chroma shift value (Rcs,h1). This has a similar intent to a high R9 or high CRI value in ensuring a light source produces a significant amount of red-hued light.

WELL also joins Title 24, NEMA, and (potentially) DLC in providing flicker guidelines. For all spaces, L07 can provide an optimization point if the flicker frequency is 90 Hz or higher from 10% to 100% light output. Alternatively, a light source with less than 5% flicker, especially below 90 Hz, can qualify.

More straightforward glare control

WELL v1 features 55 (electric light glare control) and 56 (solar glare control) have merged into L04 Glare Control. Part 1 covers solar glare, and it gives the designer a choice between window shading in all spaces or providing a glare calculation.

Part 2 covers glare from electric lighting, and it is also more straightforward than the old feature 55. Lighting designers now can choose from one of four options for minimizing electric light glare:

  • Providing 100% indirect lighting
  • Meeting predefined Unified Glare Rating values (different from feature 55 part 2a)
  • Luminaire shielding angles based on luminance (same as feature 55 part 1)
  • Luminance/intensity limits (different from feature 55 part 2b)

Although glare control is no longer a precondition for any project type, it provides up to 3 optimization points.

Visual acuity requirements to match other standards

WELL v1 feature 53 (visual lighting design) parts 1 and 3–6 defined specific intensity requirements for visual acuity in different environments.

Those requirements have been rewritten in L02 Visual Lighting Design to consult other well-known lighting references. These include the IES Lighting Handbook, the Chinese lighting code, and other localized reference works.

In addition, L02 requires a lighting plan that details strategies for task lighting, work plane heights, and appropriateness for the age of most occupants.

L02 remains a precondition, so I imagine lighting designers will be very happy with the lack of conflict with other highly-regarded lighting references.

More specific brightness management guidelines

In WELL v1, feature 53 (visual lighting design) part 2 asked the architect to provide a narrative about brightness management strategies, mostly related to managing contrasts.

That precondition has turned into a 1-point optimization, with clearer guidelines on how to manage brightness. I suspect this was done to reduce back and forth between project stakeholders.

For the most part, L06 Visual Balance defines luminance ratios for various surfaces within a room. It also discusses uniformity on ceilings, on work planes, and over periods of time.

Occupant control over lighting

L08 Occupant Control of Lighting Environments can award up to two optimization points for lighting systems that are controllable by occupants.

Part 1 provides control requirements for lighting systems that are both tunable and dimmable. One optimization point can be gained if the system is both:

  • automated to support visual and circadian requirements
  • manually controllable for both light color and intensity

Part 2 provides one optimization point if supplemental task lighting fixtures are available to light occupants. These must be able to increase the light level of a task surface to at least twice the level found in L02 Visual Lighting Design. Supplemental luminaires must be available to the occupant at no charge within eight weeks of request.

Lighting education as a requirement

WELL is about more than building spaces to meet certain health and wellness targets. It’s also about building a community of healthy people. As a result, L01 Light Exposure and Education part 2 calls for educational initiatives related to at least one of the following lighting topics:

  • the circadian rhythm and light
  • sleep hygiene
  • age-related increases in light requirements
  • the importance of daylight exposure on circadian and mental health

These initiatives could manifest in the form of signage, newsletters, or as part of a digital or physical library. Because L01 is a precondition, educational initiatives are required in all WELL v2 projects.

A major step forward

WELL v2 is undoubtedly an improvement over the original, with clearer requirements, reduced ambiguity, and more flexibility for project stakeholders. It reflects our evolving understanding of light and health, with an increased emphasis on circadian and natural light.

WELL projects already account for hundreds of millions of square feet. The changes in v2 are only going to accelerate IWBI’s mission of improving health and wellbeing in buildings throughout the world.


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I help companies create healthy lighting products. If you are considering strategy or product development in the human-centric lighting space, visit my website greg.lighting or get in touch directly.