UFC 3 -520-01
June 10, 2002
F-11.2.3 Point Calculations Using Radiosity Calculations. Commercially available
computer programs that allow for diffuse and/or specular room surfaces can perform
point calculations. These calculations i ndicate illumination at specific points and are
capable of exitance and luminance calculations as well. Some programs can
incorporate objects in space to assess the lighting in a non-empty room. Many
programs generate perspective views of illuminated rooms, which in some cases can be
realistic.
F-11.2.4 Daylighting Calculations. Refer to the IESNA Lighting Handbook. Daylight
availability can be estimated using these methods. In addition, some commercially
available computer programs will determine the contribution of daylight at a specific time
and date and under specific weather conditions. Daylight calculations are only required
when the intent of a specific building design is to provide lighting during the day
primarily by daylight.
F-11.3
Calculations of Lighting for Exterior Areas.
F-11.3.1 Point Calculations for Flood and Spot Lighting. Point calculations are a
calculation procedure that can be performed by hand or in simple, spreadsheet
formulas. They determine the illumination at a point in either the horizontal or the
vertical plane, and are reliable only for single luminaires. Manufacturers often provide
photometric data in "isocandle" form, which permits rapid assessment of the
performance of a single luminaire.
F-11.3.2 Automated Calculations for Exteriors. Point-b y-point calculations are
performed by commercially available computer programs. These programs permit
multiple luminaires and can take buildings and other obstacles into account. Most
programs generate computer aided drafti ng compatible site isolux plots and analytical
statistics related to illumination and uniformity.
F-11.4
Task Lighting Calculations. Due to near-field photometric effects, the
illumination patterns created by task lights are presently not accurately calc ulable. Task
lights should be evaluated on the basis of measured results.
F-11.5
Energy Efficiency Calculations. Perform energy efficiency calculations in
the manner and using the fo rms described in the ASHRAE/IESNA/ANSI 90.1 .
F-12
CONTROL REQUIREMEN TS FOR ELECTRIC LIGHTING.
F-12.1
Basic Principles.
F-12.1.1 Limiting the hours of operation or the light output of a lighting system can
save energy. This can be accomplished through a variety of control strategies ranging
from manual switches and dimmers to timers, and motion and light sensors. Manual
switching is the absolute minimum control and relies on personnel to manage their own
use of lighting energy. Energy codes also require that there be at least one wall switch
in each room. A simple manual dimmer, which reduces the light level from a source
F-17
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