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Lighting refers to either artificial light sources such as lamps or to natural illumination of interiors from daylight. Lighting represents a major component of energy consumption, accounting for a significant part of all energy consumed worldwide. In major cities, light pollution is of growing concern. Artificial lighting is provided today by electric lights, but previously by Gas lighting, candles or oil lamps. Proper lighting can enhance task performance or aesthetics, while there can be energy wastage and adverse health effects of lighting. Indoor lighting is a form of fixture or furnishing, and a key part of interior design. Lighting can also be an intrinsic component of landscaping.

Dark lighting in a concert hall allows laser effects to be visible
Dark lighting in a concert hall allows laser effects to be visible




Main article: Light bulb

Commonly called 'light bulbs', lamps are the removable and replaceable portion of a luminaire which converts electrical energy to both visible and non-visible electromagnetic energy. Common characteristics used to evaluate lamp quality include efficiency measured in lumens per watt, typical lamp life measured in hours, and Color Rendering Index on a scale of 0 to 100. Cost of replacement lamps is also an important factor in any design.

Energy consumption

Artificial lighting consumes a significant part of all energy consumed worldwide. In homes and offices from 20 to 50 percent of total energy consumed is due to lighting. Most importantly, for some buildings over 90 percent of lighting energy consumed can be an unnecessary expense through over-illumination (Hawken, 2000). Thus lighting represents a critical component of energy use today, especially in large office buildings where there are many alternatives for energy utilization in lighting. There are several strategies available to minimize energy requirements in any building:

  • Specification of illumination requirements for each given use area.
  • analysis of lighting quality to insure that adverse components of lighting (for example, glare or incorrect color spectrum) are not biassing the design.
  • Integration of space planning and interior architecture (including choice of interior surfaces and room geometries) to lighting design.
  • Design of time of day use that does not expend unnecessary energy.
  • Selection of fixture and lamp types that reflect best available technology for energy conservation.
  • Training of building occupants to utilize lighting equipment in most efficient manner.
  • Maintenance of lighting systems to minimize energy wastage.

Health effects of lighting

It is valuable to provide the correct light intensity and color spectrum for each task or environment. Otherwise, energy not only could be wasted but over-illumination can lead to adverse health and psychological effects.

Specification of illumination requirements is the basic concept of deciding how much illumination is required for a given task. Clearly, much less light is required to illuminate a hallway or bathroom compared to that needed for a word processing work station. Prior to 1970 (and too often even today), a lighting engineer would simply apply the same level of illumination design to all parts of the building without considering usage. Generally speaking, the energy expended is proportional to the design illumination level. For example, a lighting level of 80 footcandles might be chosen for a work environment involving meeting rooms and conferences, whereas a level of 40 footcandles could be selected for building hallways. If the hallway standard simply emulates the conference room needs, then twice the amount of energy will be consumed as is needed for hallways. Unfortunately, most of the lighting standards even today have been speciifed by industrial groups who manufacture and sell lighting, so that a historical commercial bias exists in designing most building lighting, especially for office and industrial settings. Beyond the energy factors being considered, it is important not to overdesign illumination, lest adverse health effects such as headache frequency, stress, and increased blood pressure be induced by the higher lighting levels. In addition, glare or excess light can decrease worker efficiency (DiLouie, 2006).

Analysis of lighting quality paricularly emphasizes use of natural lighting, but also considers spectral content if artificial light is to be used. Not only will greater reliance on natural light reduce energy consumption, but will favorably impact human health and performance. For example, it is clear that student test scores are improved for children who learn in the presence of greater natural light (Bain, 1997).

Professional organizations

The Illuminating Engineering Society of North America (IESNA), in conjunction with organizations like ANSI and ASHRAE, publishes guidelines, standards, and handbooks that allow categorization of the illumination needs of different built environments. Manufacturers of lighting equipment publish photometric data for their products, which defines the distribution of light released by a specific luminaire. This data is typically expressed in standardized form defined by the IESNA.

The International Association of Lighting Designers (IALD) is an organization which focuses on the advancement of lighting design education and the recognition of independent professional lighting designers. Those fully independent designers who meet the requirements for professional membership in the association typically append the abbreviation IALD to their name.

The National Council on Qualifications for the Lighting Professions (NCQLP) offers the Lighting Certification Examination which tests rudimentary lighting design principles. Individuals who pass this exam become ‘Lighting Certified’ and may append the abbreviation LC to their name. This certification process is the only national examination in the lighting industry and is open not only to designers, but to lighting equipment manufacturers, electric utility employees, etc. Generally speaking there is no legal or practical requirement for the lighting design team to possess the certifications discussed; in fact, some of the best lighting designs have been produced by architects or physicists who are unfettered by historical conventions rooted in the 1950s as are many ways of thinking of IESNA and IALD.

See also

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