22 August 2006
AMBIENT/TASK/ACCENT SYSTEMS. A lighting system made up of layers
of ambient light, task light, and accent light improves the visual comfort in a space as
well as reduces the amount of lighting energy used. Lighting with these three layers
balances the contrast ratios between objects in an occupant's field of view, adds some
visual interest, and provides flexibility in controlling what is lighted. This approach also
lowers the amount of energy consumed for lighting. By providing task lighting only
where required, the ambient light level can be much lower. For example, an entire open
office does not need to have a light level suitable for reading detailed tasks, only the
desktops. In such a case the ambient level may be low, with task lighting increasing the
light to necessary levels at the necessary locations.
Additionally, when the system is designed with these "sub-systems", greater
control flexibility results in greater opportunity for reducing energy use. Task lighting
can be turned off at a workstation not in use. This control flexibility also results in
extensive research to determine how personally controlled and "ergonomic" lighting
affects productivity and occupant comfort.
Ambient lighting provides general illuminance and surface brightness for
wayfinding and transitional tasks. Lighting high reflectance surfaces will create the
perception of brightness and provide enough ambient light for a space.
Task lighting increases the illuminance of a particular task at close range.
The type of lighting and the light level vary with the task. General reading will require a
lower light level than detailed accounting tasks. Computer use may require light on an
adjacent written task, but not on the computer screen itself.
Accent lighting highlights particular architectural features or artwork. If the
ambient light level is too high, no amount of accent lighting will increase the brightness
of a feature enough to make the contrast apparent. Selective use of accent lighting also
increases its effect. Too much accent lighting will wash out the impact of any single
Considerations to incorporate ambient/task/accent systems:
Design a lighting system to provide a minimal amount of ambient light.
Add task lighting to increase light level at the point of use. Add accent
lighting for visual interest. Refer to specific application in Chapter 6,
LIGHTING CONTROL. Controlling the electric lighting
availability and occupancy are some of the most effective methods of reducing lighting
energy and cooling loads. The heat from lighting typically accounts for 15% to 20% of a