New ways to floodlight buildings
WITH imaginative use of floodlight- ing a structure's architectural form and beauty can be effectively identified at night without distortion.
Thanks to modern developments in light sources, luminaires and techni- ques, lighting can be tailored to the type of building. But there are of course certain basic principles to follow, the first being that the building surface should have such a brightness that it appears in perspective when viewed from a distance. Shadows cast should look like those cast by the sun; they should not destroy the basic form and depth of the building's architecture.
Walls and other flat surfaces should be illuminated to a level that reveals their texture and the character of the architectural design. And finally, the building should be identified with the area about it by illuminating sufficient surrounding areas; that is, it should not appear suspended but rather oriented with adjacent grounds and plazas.
The basic categories of light source
Table 1. Comparison of light sources
are incandescent, fluorescent and mer- cury-vapour lamps (table 1). The lamps are applied in various kinds of fixtures, with the combination of lamp and fix- ture known as a luminaire (table 2). Final choice of lamp type and luminaire depends on economics, maintenance characteristics, colour, size, available floodlight locations and, above all, the aesthetic achievement desired.
Incandescent lamps are perhaps the inost useful and versatile floodlight sources. Their light can be directed easily by lenses and reflectors in beams of the desired shape, and the colour of their light is accepted as "white" Efficiency usually is about 20 lumens per watt.
Quartz-iodine lamps, the newest in- candescent sources, have efficiencies of about 25 lumens per watt. They con- tain iodine that continually removes vapourized tungsten deposits from the quartz envelope and redeposits it on the filament; consequently, they pro- vide more light in their lifetimes than
Incandescent
Mercury
Standard
Quartz- Fluor Standard Metallic Iodine escent
Additive
Initial Cost
Low
Low Higher
Higher
Higher
High- Pressure Sodium
Higher
Annual Opera- ting Cost
Medium
Medium
Low
Low
Low
Low
Service Life
Fair
Fair
Good
Very good Good
Good
Colour
Good
Definition
Very good
Fair
Fair
Good
Good
Beam Control Very good
Good
Poor
Fair
Good
Good
Cold Weather
Operation
Very good Very good
Fair
Good
Good
Good
Long Range
Projection
Very good
Fair
Poor
Fair
Fair
Fair
(narrow beam)
Medium Range Projection
Good
Good
Fair
Good
Good
Good
Lumen Output
Fair
Fair
Fair
Good
Very good
Best
PANAM
Pan Am Building is floodlighted evenly by luminaires aimed upward from the tenth floor setback. Special 2000W incandescent lamps were developed for the purpose
other incandescent types because their light output remains almost constant instead of diminishing as a result of tungsten depositing on the envelope.
The lamps used for building flood- lighting are usually about the size and shape of pencils. Most floodlights de- signed for these linear light sources develop rectangular beam patterns, which are highly efficient for many building floodlighting applications.
Fluorescent lamps are lower in brightness than the other light sources, but more efficient than most (about 75 lumens per watt). The "cool white" type renders colour well. Fluorescent lamps require a large specular reflector for precise control of light but, even with such a reflector, control is limited to the light perpendicular to the length of the lamp.
Fluorescent lamps are sensitive to temperature both in starting and oper ating, although outdoor type ballasts ensure reliable starting down to 20 degrees F. Regardless of ballast type, however, light output is reduced when the lamp is exposed to low tempera- ture and moving air. This effect is mini-
Far East BUILDER, December 1968
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