UFC 3-530-01
22 August 2006
Luminance of Room Surfaces: Downlighting the volume of a space from a
high ceiling consumes a lot of energy. Lighting the wall and ceiling surfaces
can achieve increased brightness with less energy. Typically people spend
a limited amount of time in such spaces and are not occupied with difficult
visual tasks. Therefore, the luminances of the surfaces are far more
important than the horizontal illuminance.
Color Appearance (and Color Contrast): The color of accent walls,
architectural features, and artwork needs to be rendered accurately. For
this reason, tungsten halogen, fluorescent or ceramic metal halide lamps
with a high color-rendering index (CRI) should be used to accent such
features.
Modeling of Faces or Objects: Ambient lighting for lobby spaces should
include indirect lighting and come from multiple directions and angles. For
example, if multiple systems such as sconces, pendants, and wallwashers
all provide light from multiple directions, three-dimensional objects will
appear three dimensional in form. However, if all of the lighting is aimed
straight down at the floor, objects in the space will have harsh shadows and
appear "flat".
Target Horizontal Illuminance ( 10%): 100 lux (10 fc)
DISCUSSION:
As in most interior spaces, lobbies require the lighting of surfaces as opposed to
volumes. In such high spaces, high wattage downlights are often recessed into the
ceiling and aimed at the floor. After traveling through the entire volume of the space,
very little light reaches the floor only to illuminate a low reflectance surface. Downlights
can also create harsh shadows on people and objects.
A more effective and energy efficient lighting scheme illuminates high reflective surfaces
as well as specific features in an ambient / accent approach. In the figure above,
decorative pendants light the ceiling. This ambient system also can be easily integrated
with the available daylight in the space. Wall washers illuminate walls and artwork and
sconces identify the elevator doors, assisting in wayfinding for building visitors.
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