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Visual lighting design

Features/Light/Feature 53

Visual lighting design

Intent: 

To support visual acuity by setting a threshold for adequate light levels and requiring luminance to be balanced within and across indoor spaces.

BACKGROUND

Adequate light levels are needed for a broad variety of activities, including reading various qualities and types of print, and working on detail-oriented tasks. Brightness levels also contribute to the perception of spaciousness, as well as to the overall visual appeal of illuminated spaces. Targeted task lighting can provide the necessary amount of light at workspaces without over-illuminating ancillary spaces; ambient light levels of 300 lux are sufficient for most tasks. Pairing adjustable direct task lighting with indirect or diffuse ambient lighting allows user customization and good visual acuity while providing more suitable background light. Light intensity for visual acuity is measured in lux (or foot candles), which is a measure of the way the eye responds to light weighted to the response of the cone cells—the main photoreceptors for daytime vision, located on the retina of the human eye.

Part 1
Visual Acuity for Focus

The following requirements are met at workstations or desks:
a.
The ambient lighting system is able to maintain an average light intensity of 215 lux [20 fc] or more, measured on the horizontal work plane. The lights may be dimmed in the presence of daylight, but they are able to independently achieve these levels.
b.
The ambient lighting system is zoned in independently controlled banks no larger than 46.5 m² [500 ft²] or 20% of open floor area of the room (whichever is larger).
c.81
If average ambient light is below 300 lux [28 fc] and meets Part 1a, task lights providing 300 to 500 lux [28 to 46 fc] at the work surface are available upon request.

Part 2
Brightness Management Strategies

Provide a narrative that describes strategies for maintaining luminance balance in spaces, which takes into consideration at least two of the following:
a.174
Maximum brightness contrasts between main rooms and ancillary spaces, such as corridors and stairwells, if present. For example, projects may establish that, while still maintaining lighting variety, a main room cannot exhibit 10 times greater or lesser luminance than an ancillary space.
b.174
Maximum brightness contrasts between task surfaces and immediately adjacent surfaces, including adjacent visual display terminal screens. For example, projects may establish that, while still maintaining lighting variety, a surface cannot exhibit 3 times greater or lesser luminance than an adjacent surface.
c.174
Brightness contrasts between task surfaces and remote, non-adjacent surfaces in the same room. For example, projects may establish that, while still maintaining lighting variety, a surface cannot exhibit 10 times greater or lesser luminance than another remote surface in the same room.
d.174
The way brightness is distributed across ceilings in a given room that maintains lighting variety but avoids both dark spots, or excessively bright, potentially glaring spots. For example, projects may establish that, while still maintaining lighting variety, one part of the ceiling cannot be 10 times greater or lesser luminance than another part of the ceiling in the same room.

Part 3
Commercial Kitchen Lighting

The following light levels are achieved:
a.123
Maintained average of at least 500 lux [46 fc] of lighting at countertops and other food preparation or production areas.
b.124
Maintained average of at least 200 lux [18 fc] of lighting in dishwashing areas.

Part 4
Visual Acuity in Living Environments

One or more light sources provide the following:
a.
Maintain an average of 215 lux [20 fc] as measured 0.60 m [24 inches] above finished floor in the living room.
b.
Maintain an average of 50 lux [5 fc] as measured 0.60 m [24 inches] above finished floor in the bedroom.
c.
Maintain an average of 100 lux [9 fc] as measured at finished floor in the bathroom.

Part 5
Visual Acuity for Learning

The ambient lighting system at desks in classrooms for the specified age groups meet the following requirements:
a.
Early education, primary and secondary schools, and adult education for students primarily under 25 years of age: Able to maintain an average of 175 lux [16 fc] or more measured on the horizontal plane, typically 0.76 m [30 inches] above finished floor. The lights may be dimmed in the presence of daylight, but they are able to independently achieve these levels.

Part 6
Visual Acuity for Dining

The ambient lighting system at dining surfaces for the specified restaurant types meet the following requirements:
a.174
Cafeterias: Able to maintain an average of 150 lux [14 fc] or more measured on the horizontal plane at the height of the dining surface. The lights may be dimmed in the presence of daylight, but they are able to independently achieve these levels.
b.174
Casual dining and fast food: Able to maintain an average of 100 lux [9 fc] or more measured on the horizontal plane at the height of the dining surface. The lights may be dimmed in the presence of daylight, but they are able to independently achieve these levels.
c.174
Fine dining: Able to maintain an average of 30 lux [3 fc] or more measured on the horizontal plane at the height of the dining surface. The lights may be dimmed in the presence of daylight, but they are able to independently achieve these levels.