I.6 Quality Lighting

Intent
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. Quality lighting enhances and contributes to creating the perception of a 'bright and cheery' workplace through volumetric brightness by illuminating upper wall areas and ceiling planes.

Required Performance Criteria

1. Newly installed electric lighting must be operable in multiple modes 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

2. 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 ft or more from a wall.
3. Consult the current version of the IESNA handbook for other recommended light levels. You may design closer to the minimum recommended values to reduce the connected load and conserve energy, but in this case note that the contrast ratios in item D below become even more important to maintain, and the overall volumetric rendering should be bright.
4. Keep contrast ratios in the field of view within the space as seen from the task areas to no greater than 10:1
5. Achieve a Color Rendering Index (CRI) for each space type based on recommendations in the current version of the IESNA handbook.

Methods:

6. At a minimum, conduct a point-by-point analysis of horizontal illumination levels at the work plane in each lighting mode for each space.
7. Preferably, use a computer program to determine the performance characteristics of the electric lighting system in each primary space type. Computer models should be used to analyze illumination levels on vertical planes when they have been defined as a task or work area.

Compliance Tools and Resources

• Rea, M. S., ed. IESNA Lighting Handbook, Ninth Edition. New York: Illuminating Engineering Society of North America, 2000.
• Lighting design tables, luminaire specification sheets.
• Lighting design software including Lumen Micro 2000, Lumen Designer, AGI32, Radiance, Desktop Radiance, LightPro and Luxicon