22 August 2006
Light Distribution on Task Plane (Uniformity): Avoid uneven lighting such
that some desks are significantly brighter than other desks. This occurs
with either direct sunlight falling onto desks, or with recessed direct
parabolics. Indirectly lighting the classroom with no more than 50% direct
light provides the most uniform lighting.
Horizontal and vertical illuminance: Horizontal illuminance is important for
the student's desks. Vertical illuminance is important to view instructors,
students, and the white boards.
Target Horizontal Illuminance ( 10%): 500 lux (50 fc)
Multiple studies done show improved test scores (over 20%) with students who are in
classrooms with daylight. Orient classrooms so that daylight can enter the classroom,
preferably from two directions, without direct glare.
The electric lighting should light the ceiling in order to reduce direct and reflected glare
potential. Yet, some direct light component is important to balance out the luminances
within the classroom. The use of a white board light has been shown to improve
student retention by highlighting written information.
Controls in the classroom are also important, especially with the increase in computer
projection. Giving the teacher the ability to dim the lighting provides enough light for
note taking, yet minimizes the direct glare on the screen. Consider occupancy sensors
for infrequently used classrooms.
RULES OF THUMB:
Pendant spacing: When beginning a design, start with 3.0 3.7 m (10 12
ft) spacing for T8 fixtures and modify accordingly to meet critical design
Pendant length: Pendant lengths range from 0.5 0.9 m (18 in 3 ft).
High performance luminaires may achieve a minimum of 0.3 m (12 in)
pendant lengths. Specialty luminaires for low ceiling applications may be
mounted even closer to the ceiling.
Lighting Power Density: The lighting power density for open office areas
can range from 1.2 1.5 watts /sq ft for ambient connected load.