Civil Engineering Reference
In-Depth Information
Reflectance varies between 90 and 30 %; chromaticity between 2,500 and
3,000 K; and color rendering between 50 and 90.
As a general rule, with a required task surface illuminance ranging
between 1,000 and 200 lx and a lamp efficiency ranging from 50 to
100 lm/W, typical values are 20-10 W/m
2
. Of course, higher values can
be found if incandescent lamps with less than 25 lm/W are used or if high
levels of illumination are recommended for particular task surfaces.
Fig. 14.1
Example of curves of the depreciation factor (ratio between the illumination provided
at various points in time and that provided by the new system; it is expressed as a percentage)
Table 14.1
Recommended task surface illuminance
Recommended illuminance
lx
Task surface
fc
Very difficult task
1,000-4,000
93-372
Commercial surfaces
750-1,000
70-93
Material test, drawing, sewing, etc.
750-1,500
70-140
Office room
250-750
23-70
Transit area
50-150
5-15
