This is a legacy version of the WELL Building Standard. Please check the latest version here.

Circadian lighting design

Circadian lighting design


To support circadian health by setting a minimum threshold for daytime light intensity.

Yes. For standing or adjustable desks, the vertical plane of measurement would be .46 m [18 inches] above the work surface, for example 1.58 m [62 inches] above the finished floor if a standing desk is fixed at 1.12 m [44 inches].

The owner must provide a compliant lighting system throughout the entire building, including all tenant spaces. Access to tenant spaces is required to conduct testing during Performance Verification, however, lighting provided by the tenant (if any) within their leased space is excluded.

Projects must consistently apply definitions to their spaces across all features. Thus, if conference tables, breakout tables, or standing desks are also are characterized as "workstations" to comply with Feature 73 (and/or Feature 71), they are also considered workstations for the purposes of Feature 54.

Part 1a allows calculations and measurements to use daylight, which can be beneficial to projects with many windows. Part 1b only uses electric light, so outside conditions will not influence the performance results when tested. The WELL Assessor will test for both pathways while on site to determine if the project passes either requirement.

Yes, computer screens can be included in calculations. Project teams are responsible for ensuring computer screens are turned on during Performance Verification.

Please review the Circadian Lighting Appendix L1 and L2 for a detailed account of how circadian lighting can be measured. Note that the circadian light level must be simulated on a vertical plane at the occupant's eye level.

To learn more about circadian lighting and how it is measured, please review the Circadian Lighting Tables L1 and L2.

The circadian lighting levels created by the lighting system are dependent on the spectral power distribution of the light source used. Light sources with a higher melanopic ratio will produce more EML at a given brightness. As a rule of thumb, high correlated color temperature lamps and light fixtures tend to have higher melanopic ratios, but in the lighting model, project teams should calculate the melanopic ratio for the specific lights selected for use.

In order to fully verify your lighting strategy, a lighting model that takes into account all relevant light sources should be conducted to ensure that the required light levels are met at all the workstations on the vertical plane where the occupant's eyes would typically be.

A lighting designer is not required to be a part of the project design team, however, they may be helpful if no one on the project team has specific experience with lighting models or with circadian lighting design.

A project is not required to provide EML calculations or modeling; the only documentation required for this feature is a Letter of Assurance from the architect or lighting consultant.

The WELL assessor will verify that the levels are being meet through onsite spot checks of the light levels. Therefore, project teams are strongly encouraged to run their own calculations and to consider modeling so that they are confident they are meeting the lighting levels required of the feature before the WELL assessor comes on site.