Guideline I.5: Quality Lighting
Electric lighting should be designed to supplement and support the use of daylight as the primary source of light for visual tasks. This is vitally important to achieving environmental, health and economic goals. The integrated design of artificial and natural light must also maintain these lighting quality characteristics and effects: tolerable glare, natural color rendering, and attractive illumination of people for social exchanges.
Required Performance Criteria
Guidelines apply to all projects designated New Buildings and for Major Renovations with lighting replacement in the project scope.
- Newly installed electric lighting must be operable in multiple modes and responsive to both daylight zones and differentiated uses within a given space, such as separating controls for media projection areas from general task areas within a space.
Recommended Performance Criteria
- For general illumination in most space types, attain an average electrical illumination at the work plane of 35 to 50 foot-candles. A minimum of 25 foot-candles is recommended at any point 3 feet or more from a wall.
- Consult the current version of the Illuminating Engineering Society of North America (IESNA) handbook for other recommended light levels.
- Keep contrast ratios in the field of view within the space as seen from the task areas to no greater than 10:1
- Achieve a Color Rendering Index (CRI) for each space type based on recommendations in the current version of the IESNA handbook.
- At a minimum, conduct a point-by-point analysis of horizontal illumination levels at the work plane in each lighting mode for each space.
- Perform computer simulation of the performance characteristics of the electric lighting system in each primary space type. Illumination levels on vertical planes should be evaluated when they have been defined as a task or work area.
Implementation in the Design Process:
Incorporate performance criteria into lighting design criteria in program document. Develop additional quality lighting criteria as needed for special facility issues. For example, security or anti-vandalism lighting may need to be incorporated into lighting considerations.
The design may be closer to the minimum recommended handbook illumination values to reduce the connected load and conserve energy; note that if this is the case the contrast ratios in become even more important to maintain, and the overall volumetric luminance should be considered.
Conduct a first order check during Design for design constraints on lighting design. Ensure that general daylighting schemes and lighting plans are not in conflict with achieving lighting quality and any additional lighting criteria.
During early design, as fixtures types and fixtures are being selected complete a lighting analysis and develop the lighting design in conformance with performance criteria. Perform any lighting modeling studies as needed to confirm or substitute for calculations.
During construction observe and verify that the room, window, finish, and lighting variables (upon which estimated compliance was based) are proceeding according to goals as reflected in drawings and specifications.
Conduct onsite measurements once all lighting is operational during construction administration.
- I.5A: Verification that the lighting system designed with multiple modes.
- I.5B: Verification that the work plane illumination is within guideline limits.
- I.5C: Verification that the illumination levels within guideline limits.
- I.5D: Verification that the contrast ratios levels within guideline limits.
- I.5E: Verification that the CRI provided by lighting within guideline limits.
- I.5F: Verification of analysis of horizontal illumination levels.
- I.5G: Verification of modeled determination of illumination levels.
Rea, M. S., ed. IESNA Lighting Handbook, Tenth Edition. New York: Illuminating Engineering Society of North America, 2011: https://www.ies.org/store/lighting-handbooks/lighting-handbook-10th-edition/
Tillman, Barry. 2016. Human Factors and Ergonomics Design Handbook, Third Edition, Barry Tillman. McGraw-Hill, NY.