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The locations for floodlighting units should be selected so that the desired lighting effect will be obtained, but one is often restricted in the actual positions available. The next few paragraphs present rules of floodlighting design which might almost be called fundamental, together with suggestions on equipment location and mounting.
Buildings--Uniform Illumination
Buildings of simple treatment require substantially uniform illumination. This is generally best obtained by locating the floodlights on roofs of buildings directly opposite and not more than 150 or 200 feet away. When the length of building face to be illuminated is not greater than the distance of the floodlights from the building, the units can be placed in one group. Otherwise the units should be divided into two or more groups, thereby obtaining more efficient utilization of the light and avoiding sharp shadows from recessed windows and ledges.
A typical bank of projectors for lighting a building uniformly
Small stores, theatres, and other buildings of two or three stories can be lighted quite successfully, when positions across the street are not available, by means of floodlights placed on wide marquees or on ornamental standards set at the curb. The shadows are apt to be rather heavy, but by distributing the units as evenly as possible along the front to be lighted, fair uniformity can be obtained. In general, buildings over four stories in height cannot be lighted successfully by marquee or curb post units.
An attractive installation of curb post floodlighting units
Whenever a building is to be lighted uniformly, at the top and sides of the building there is always a certain amount of waste light which reduces the computed level of illumination. This loss is compensated for to a considerable extent by the spill light outside of the 10 per cent zone, especially where the projectors are located close to the area to be lighted.
Buildings--Non-Uniform Illumination
Skyscraper architecture lends itself to non-uniform illumination, silhouette, and shadows. Ledges formed by setbacks offer ideal locations for floodlights. The units should usually be placed immediately inside and below the parapet. In northern climates they should be elevated sufficiently above the roof slab to be above drifting snow. Elevation above the roof slab as far as practicable without exposure to view above the parapet also permits easy maintenance and does not subject the units to immersion in trash or rain water. The electrical conduit can be embedded in or mounted on the parapet, or it can be carried by the structure supporting the floodlights. The latter method is cheaper and allows for considerable revision of the lighting installation with little expense.
A bank of floodlight projectors mounted inside the parapet
Battery of projectors for floodlighting the A.E. Staley Building, Decatur, Ill.
reproduced from:
General Electric's Incandescent Lamp Department's Guide to Floodlighting
by O.F. Haas and K.M. Reid
Cleveland
1931
Copyright 2001 VISUAL TERRAIN, INC.
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