22 August 2006
INTRODUCTION. This chapter identifies typical interior facility applications
and explains the critical design issues for each as outlined in the Quality of the Visual
Environment chapter of the Lighting Handbook. Each application details a conceptual
lighting design for a sample space with a sketch and equipment recommendation. This
sample represents one solution that addresses the design issues and meets the
appropriate criteria. It is not the only solution and alternate schemes will result in
LIGHTING CALCULATIONS FOR INTERIOR SPACES.
Criteria. Lighting for interior areas is measured with a variety of parameters.
Maximum, minimum, and average illuminance values are often listed as target criteria.
Uniformity criteria may be described with multiple terms including maximum to minimum
and maximum to average. The most appropriate criteria vary with the type of
application. The following lists this UFC's interpretation of the IESNA criteria and how it
is used in the applications shown in this chapter:
Minimum illuminance: This provides the low end of the range of acceptable
light levels. This is typically used to define the light level required to
perform a specific task.
Maximum illuminance: This provides the high end of the range of
acceptable light levels. This is typically used to prevent overlighting of an
Average illuminance: This criterion is typically used to give an approximate
light level. Unless noted otherwise, the values given in this chapter
designate an average illuminance value.
Maximum to minimum uniformity: This is typically used to prevent
excessive contrast. This is most important in work areas where individuals
will spend large amounts of time such as office spaces.
Lumen Method. The lumen method is a calculation procedure that can be
performed by hand or by simple, spreadsheet formulas. It determines the average
illuminance in a space, and is reliable only for spaces with a regular and uniform "grid"
of luminaires in which general lighting, providing task light levels everywhere, is
appropriate. The lumen method also can be used for determination of "ambient"
illumination in rooms in which localized "task lights" are used strictly for task light. Refer
to IESNA RP-23 or the Lighting Handbook for additional information.
Point Calculations Using Flux Transfer Calculations. Commercially available
computer programs that assume Lambertian (matte or flat) room surfaces can perform