Luminaires & Distribution
Last Update: October 30, 2010
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Luminaire Selection

Because of the decisive role that luminaires play in the overall efficiency of the lighting system and its ability to satisfy the design intent and owner’s operational needs, designers must select luminaires carefully, taking into account many factors. These include efficiency, components, construction, optical and glare control, distribution pattern, aesthetics and architectural integration, ease of installation and maintenance, special concerns such as safety and hazardous conditions—to name a few! Once the application needs are understood, the right combination of these factors can be determined and good luminaire candidates identified.

This section begins with an in-depth discussion of the photometric report, a staple tool that provides standardized testing data describing a given luminaire’s light distribution, which can be used in lighting design calculations. Using the photometric report, the designer can quickly analyze the direction and intensity of light emitted by the luminaire, and determine how much light will be delivered to task and space surfaces. The designer can also determine spacing criteria for some interior luminaires, luminaire and overall application efficiency, and the likelihood of the luminaire producing offensive direct glare to users. Because photometric reports do not take into account light loss factors such as ballast factor, these are provided and explained so that proper adjustments can be made.

Besides photometric performance, other selection criteria are also critically important, including ease of maintenance, cost and sustainability aspects such as durability of materials and components, luminaire recycling, packaging waste and use of energy and toxic materials in manufacturing—all of which are explored in this section. Aspects that are particularly important for new solid-state products (such as LED luminaires) are thoroughly explored, such as glare, color and thermal management.

Performance Criteria
Lighting specifiers have the confusing task of choosing among the vast number of luminaires on the market. Advanced lighting design involves evaluating the luminaire’s construction, ease of installation, durability and performance against the lighting quality criteria.
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Photometric Data
"Photo" means light; "metric" means measurement. Photometric data describe the luminaire’s light distribution, the direction and intensity of light emitted by a luminaire. This information is used in lighting design and calculations.
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Maintenance & Durability 
The most beautiful, energy-efficient lighting system will soon be worthless if it cannot be easily maintained. It makes no sense to mount a luminaire with short lamp life over a staircase, where relamping requires expensive scaffolding. Street lighting with an historic look will soon be replaced with more common cobra heads if the utility maintenance person cannot get his or her gloved hand into the optical chamber to unscrew the burned-out lamp.
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Luminaires & Sustainability 
Although energy consumption has the greatest overall impact to the environment with regard to lighting use, there are other sustainability issues to consider when selecting a luminaire.
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LED Luminaire Issues 
Light emitting diodes (LED) or solid state lighting (SSL) can often be evaluated with many of the same tools and guiding principles used for ‘traditional’ non-LED source technologies.  There are, however, unique aspects of SSL luminaires that do require evaluation when they are considered for any particular application.  
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Cost Strategies 
Energy-efficient lighting can be a hard sell because the initial cost of purchasing and installing the lighting equipment and controls is likely to be higher than the cost of a less-efficient system.  
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