Over-illumination - AbsoluteAstronomy.com

Over-illumination is the presence of lighting intensity (illuminance

Illuminance

In photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of the intensity of the incident light, wavelength-weighted by the luminosity function to correlate with human brightness perception. Similarly, luminous emittance is the luminous flux per...

) beyond that required for a specified activity. Over-illumination was commonly ignored between 1950 and 1995, especially in office and retail

Retail

Retail consists of the sale of physical goods or merchandise from a fixed location, such as a department store, boutique or kiosk, or by mail, in small or individual lots for direct consumption by the purchaser. Retailing may include subordinated services, such as delivery. Purchasers may be...

environments; only since then has the interior design

Interior design

Interior design describes a group of various yet related projects that involve turning an interior space into an effective setting for the range of human activities are to take place there. An interior designer is someone who conducts such projects...

community begun to reconsider this practice.

The concept of over-illumination encompasses two separate but related concerns:

Use of more artificial illumination than required is expensive and energy-intensive. This includes consideration both of the appropriate level of illumination when spaces are in use, and when they are unoccupied.
Clinical studies show that excessive levels of artificial light produce annoyance and health effects in a large fraction of the population. These effects may depend on the spectrum
Spectrum
A spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...

of the light as well as the overall brightness.

Lighting accounts for roughly 9% of U.S. residential electricity use and close to 40% of U.S. commercial building electricity use. Money and energy could be saved by, for example, turning off office building lights overnight, using natural light whenever possible, and taking full advantage of occupancy sensors or simply flipping manual light switches in unoccupied spaces. In response to these concerns, the design and architecture

Architecture

Architecture is both the process and product of planning, designing and construction. Architectural works, in the material form of buildings, are often perceived as cultural and political symbols and as works of art...

communities are making greater use of indirect sunlight

Daylight

Daylight or the light of day is the combination of all direct and indirect sunlight outdoors during the daytime. This includes direct sunlight, diffuse sky radiation, and both of these reflected from the Earth and terrestrial objects. Sunlight scattered or reflected from objects in outer space is...

in modern commercial buildings.

Numerical definition

Generally speaking, under-illumination occurs indoors when light levels fall below 320 lux for general office use. Task lighting levels of just 75 lux to 100 lux are not uncommon in contemporary office environments. For comparison, the midday sun provides about 32,000 to 100,000 lux depending on latitude, time of year and cloud cover. The term over-illumination first came into reasonably broad use in the early 1990s, when the lighting, health and energy conservation

Energy conservation

Energy conservation refers to efforts made to reduce energy consumption. Energy conservation can be achieved through increased efficient energy use, in conjunction with decreased energy consumption and/or reduced consumption from conventional energy sources...

fields realized its effects. Production of glare

Glare (vision)

Glare is difficulty seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. Because of this, some cars include mirrors with automatic anti-glare functions....

is a de facto

De facto

De facto is a Latin expression that means "concerning fact." In law, it often means "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established." It is commonly used in contrast to de jure when referring to matters of law, governance, or...

indication of over-illumination, since that causes optical processing conflicts and confusion to the brain in processing optical inputs. Over-illumination is sometimes grouped with unnatural spectra because negative health effects may result from the excess illumination, and also because certain artificial lights (such as fluorescent lamp

Fluorescent lamp

A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful...

s) provide intense illumination in certain frequency bands, unlike daylight, whose spectral power distribution

Spectral power distribution

In color science and radiometry, a spectral power distribution describes the power per unit area per unit wavelength of an illumination , or more generally, the per-wavelength contribution to any radiometric quantity .Mathematically, for the spectral...

is fairly even over the visible spectrum. The most desirable spectrum is that of natural light

Natural light

Natural light can mean:*Sunlight*Moonlight*Natural Light Beer a product made by Anheuser-Busch....

, which the body is attuned to and uses to set the circadian rhythm

Circadian rhythm

A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...

Related phenomena

Over-illumination can contribute to light pollution

Light pollution

Light pollution, also known as photopollution or luminous pollution, is excessive or obtrusive artificial light.The International Dark-Sky Association defines light pollution as:...

, where stray light

Stray light

Stray light is light in an optical system, which was not intended in the design. The light may be from the intended source, but follow paths other than intended, or it may be from a source other than the intended source...

illuminates the outdoors or others' property, where it is unwanted. Over-illumination is a topic normally addressed in the process of building design, whereas light pollution is normally addressed by zoning regulations.

Furthermore, over-illumination generally does not refer to the extreme conditions of snowblindness or arc eye, in which ultraviolet light can induce physical damage to the cornea

Cornea

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...

Causes

Lighting unoccupied areas is a significant waste of energy. Many office buildings are illuminated overnight and on weekends. In some cases, this is so that janitors working overnight do not have to bother turning lights on and off. Lighting of unoccupied areas can be reduced by installation of occupancy sensors or timers.

Energy can also be wasted by operating outdoor lighting during daylight. In many cases this arises because the lights are controlled by timers, which must be reset periodically as the times of sunset and sunrise vary throughout the year.

Retail stores, especially those with large windows, are sometimes illuminated overnight as a measure of crime prevention. The idea is that, with the lights on, burglars are visible from the outside and can raise an alarm.

Forsaking use of sunlight

Forsaking use of sunlight is often a design decision made by the architect or their subcontractor. Overlooking opportunities for skylights can be an issue with many building designs, but lack of coordination of interior light banks with indirect sunlight is even more common. At a minimum, the building design should offer sufficient independent light banks so that building occupants may select the most suitable combination of natural to augmented light. Very frequently entire floors of office buildings are designed with only one switch, so that perimeter areas near natural light are illuminated with the same level of artificial light as the dimmest interior zones. This lack of independent controls also would require an entire office floor of say 10000 square feet (929 m²) to be fully illuminated if one office worker stays late for evening work. This can occur with even the most eminent of architects. Frank Lloyd Wright

Frank Lloyd Wright

Frank Lloyd Wright was an American architect, interior designer, writer and educator, who designed more than 1,000 structures and completed 500 works. Wright believed in designing structures which were in harmony with humanity and its environment, a philosophy he called organic architecture...

designed Marin County Civic Center

Marin County Civic Center

Marin County Civic Center, the last commission by Frank Lloyd Wright, is located in San Rafael, California. Groundbreaking for the Civic Center Administration Building took place in 1960, after Wright's death and under the watch of Wright's protégé, Aaron Green, and was completed in 1962. The...

in 1957 with only one or two switches serving very large office pools. This reportedly costs Marin County

Marin County, California

Marin County is a county located in the North San Francisco Bay Area of the U.S. state of California, across the Golden Gate Bridge from San Francisco. As of 2010, the population was 252,409. The county seat is San Rafael and the largest employer is the county government. Marin County is well...

several thousand dollars per year in electricity costs.

Failure to use occupancy sensors

Occupancy sensors are used primarily for bathrooms, conference rooms and storage areas. This is an energy waste issue and not a health issue. The payback time of most occupancy sensors is in the range of two to five years, and yet first-cost economics prevent the installation of occupancy sensors in the majority of cases where they would save energy and lighting maintenance costs.

Failure to delamp or use available lighting controls

Failure to delamp or use available lighting controls is a common issue associated with over-illuminated buildings. Many instances of "designed in" over-illumination can be corrected by simple actions of building managers, following an illumination survey. In many instances over-illumination can be solved by removing a fraction of the lights or fixtures from a ceiling lighting system. In other cases a lighting retrofit can be conducted to replace older, less energy efficient fixtures with newer ones. Lighting retrofits can also be designed to reduce over-illumination; retrofits have typical payback periods of two to four years. In simpler cases many fluorescent ceiling illumination systems have multiple switch settings that allow tuning of the light intensity delivered, the most common version of this control being the "three-level switch", also called A/B switching. Much of the benefit of the excess illumination reduction comes from a better ratio of natural light to fluorescent light that can result from any of the above changes. Research has been conducted showing worker productivity gains in settings where each worker selects his or her own lighting level.

Headaches, fatigue, stress and performance effects

Health effects of over-illumination or improper spectral composition of light include increased headache

Headache

A headache or cephalalgia is pain anywhere in the region of the head or neck. It can be a symptom of a number of different conditions of the head and neck. The brain tissue itself is not sensitive to pain because it lacks pain receptors. Rather, the pain is caused by disturbance of the...

incidence, worker fatigue, medically defined stress

Stress (medicine)

Stress is a term in psychology and biology, borrowed from physics and engineering and first used in the biological context in the 1930s, which has in more recent decades become commonly used in popular parlance...

, decrease in sexual

Human sexuality

Human sexuality is the awareness of gender differences, and the capacity to have erotic experiences and responses. Human sexuality can also be described as the way someone is sexually attracted to another person whether it is to opposite sexes , to the same sex , to either sexes , or not being...

function and increase in anxiety. The health consequences are particularly significant of improperly matching the color spectrum of sunlight when illuminating the workplace.

Migraine headaches have been cited by some individuals as being caused by excessive light. In one survey over-illumination was listed as the number two trigger for migraines, with 47% of the respondents reporting bright light as the principal trigger of their migraine episode. Not only does bright light induce headache, but certain spectral distributions can increase the incidence of headache.

Fatigue is a common complaint from individuals exposed to over-illumination, especially with fluorescent media. Some studies have shown that the flicker and over-illumination combined in some fluorescent systems yield particularly high fatigue incidence. Research on circadian rhythm

Circadian rhythm

in humans indicates that one reason for fatigue stems from the incorrect color spectrum of fluorescent light.

Stress and anxiety are frequent outcomes from working in a setting of intense (especially fluorescent) lighting. Research has shown that annoyance from bright light leads to medical stress

Stress (medicine)

. It is clear that brighter, less spectrally correct light induces clinically measurable stress, and it is suggested that for children this over-illumination may interfere with the learning process. For example, children experiencing any form of stress are more likely to suffer from dysgraphia

Dysgraphia

Dysgraphia is a deficiency in the ability to write primarily in terms of handwriting, but also in terms of coherence. It occurs regardless of the ability to read and is not due to intellectual impairment...

, a problem in learning to write. Task performance can also be compromised for people conducting work under artificial (e.g. fluorescent as opposed to natural light). The annoyance with purely artificial light and preference by office workers for natural light has been demonstrated by a number of studies spanning eastern and western cultures. Fluorescent lighting has also been linked to aggravating other psychological disorders such as agoraphobia

Agoraphobia

Agoraphobia is an anxiety disorder defined as a morbid fear of having a panic attack or panic-like symptoms in a situation from which it is perceived to be difficult to escape. These situations can include, but are not limited to, wide-open spaces, crowds, or uncontrolled social conditions...

Circulatory and circadian rhythm effects

Hypertension

Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...

effects of over-illumination can lead to aggravation of cardiovascular disease

Cardiovascular disease

Heart disease or cardiovascular disease are the class of diseases that involve the heart or blood vessels . While the term technically refers to any disease that affects the cardiovascular system , it is usually used to refer to those related to atherosclerosis...

and erectile dysfunction

Erectile dysfunction

Erectile dysfunction is sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual performance....

, which impacts are outcomes of long term cumulative exposure and associated systematic increases in blood pressure. The mechanism of this effect seems to be stress by related upregulation of adrenaline

Epinephrine

Epinephrine is a hormone and a neurotransmitter. It increases heart rate, constricts blood vessels, dilates air passages and participates in the fight-or-flight response of the sympathetic nervous system. In chemical terms, adrenaline is one of a group of monoamines called the catecholamines...

production akin to the fight-or-flight response

Fight-or-flight response

The fight-or-flight response was first described by Walter Bradford Cannon....

. When adrenalin is released into the bloodstream it causes vasoconstriction

Vasoconstriction

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, small arterioles and veins. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in...

, a known precursor to both hypertension and erectile dysfunction. Analogous female sexual

Human female sexuality

Human female sexuality encompasses a broad range of behaviors and processes, including female sexual identity and sexual behavior, the physiological, psychological, social, cultural, political, and spiritual or religious aspects of sex...

side effects are thought to result in the female anatomy from reduced blood flows.

Circadian rhythm

Circadian rhythm

disruption is primarily caused by the wrong timing of light in reference to the circadian phase. It can also be affected by too much light, too little light, or incorrect spectral composition of light. This effect is driven by stimulus (or lack of stimulus) to photosensitive ganglion cells in the retina. The "time of day", the circadian phase, is signalled to the pineal gland

Pineal gland

The pineal gland is a small endocrine gland in the vertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions...

, the body’s photometer

Photometer

In its widest sense, a photometer is an instrument for measuring light intensity or optical properties of solutions or surfaces. Photometers are used to measure:*Illuminance*Irradiance*Light absorption*Scattering of light*Reflection of light*Fluorescence...

, by the suprachiasmatic nucleus

Suprachiasmatic nucleus

The suprachiasmatic nucleus or nuclei, abbreviated SCN, is a tiny region on the brain's midline, situated directly above the optic chiasm. It is responsible for controlling circadian rhythms...

. Bright light in the evening or in the early morning shifts the phase of the production of melatonin

Melatonin

Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes...

(see phase response curve

Phase response curve

A phase response curve illustrates the transient change in the cycle period of an oscillation induced by a perturbation as a function of the phase at which it is received...

). An out-of-sync melatonin rhythm can worsen cardiac arrhythmias and increase oxidized

Redox

Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....

lipid

Lipid

Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...

s in the ischemic

Ischemia

In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...

heart

Heart

The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

. Melatonin also reduces superoxide

Superoxide

A superoxide, also known by the obsolete name hyperoxide, is a compound that possesses the superoxide anion with the chemical formula O2−. The systematic name of the anion is dioxide. It is important as the product of the one-electron reduction of dioxygen O2, which occurs widely in nature...

production and myeloperoxide (an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

in neutrophils which produces hypochlorous acid

Hypochlorous acid

Hypochlorous acid is a weak acid with the chemical formula HClO. It forms when chlorine dissolves in water. It cannot be isolated in pure form due to rapid equilibration with its precursor...

) during ischemia-reperfusion.

In practice, adverse outcomes seem to arise most commonly among workers subject to intense fluorescent light, which is poorly matched to the spectrum of sunlight. According to one set of researchers, the body translates this condition as "total darkness" and resets the circadian clock incorrectly. Not only does this result in fatigue

Fatigue (physical)

Fatigue is a state of awareness describing a range of afflictions, usually associated with physical and/or mental weakness, though varying from a general state of lethargy to a specific work-induced burning sensation within one's muscles...

, but also immuno-suppressive behavior that has been shown to be linked to increased cancer

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

s. The research indicates that increasing the ratio of natural light to artificial solves much of the problem, provided the total illumination level is not driven excessively high. Many of these health impacts may be primarily due to the spectrum of the light rather than the overall level of illumination, but more research is required to establish this.

Energy and economic considerations

Excessive energy use is often tolerated because the person who bears the cost is not the one making day to day decisions about lighting. Building managers and not building owners usually structure such things as janitorial use of lighting, setting or installation of timers, or the choice of lighting fixtures. Another contributor is a leasing structure, common in the U.S., where the tenant pays none of the electricity costs.

There are also myths which continue to propagate, including better lighting decisions. One such is the idea that it costs more to turn fluorescent lighting off and on again than to keep it running. According to the U.S. Department of Energy, the amount of electricity consumed in lighting up a fluorescent lamp is equal to a few seconds or less of normal operation. Taking into account the extra wear on the bulb caused by turning it off and on, the lamp has to not be needed for between five and fifteen minutes, depending on the type of lamp and other factors. Another myth is that more light is better, which is contradicted by health data.

Architectural design can identify technological aspects of window

Window

A window is a transparent or translucent opening in a wall or door that allows the passage of light and, if not closed or sealed, air and sound. Windows are usually glazed or covered in some other transparent or translucent material like float glass. Windows are held in place by frames, which...

design where window angles can be calculated to minimize interior glare and reduce interior over-illumination, while at the same time reducing solar heat loading and subsequent demand for air conditioning as energy conservation techniques. For the Dakin Building

Dakin Building

The Dakin Building is an architectural award-winning class A office building on the San Francisco Bay in Brisbane, California. Serving as a corporate headquarters building for several companies of national prominence, it was built from the profits of the Garfield character whose licensed products...

in Brisbane, California

Brisbane, California

Brisbane is a small city located in the northern part of San Mateo County, California on the lower slopes of San Bruno Mountain. It is on the northeastern edge of South San Francisco, next to the San Francisco Bay and near the San Francisco International Airport.The population was 4,282 as of...

the angled window projections effectively provide permanent sunscreens, obviating interior blinds or shades.

Building and lighting control systems

Building automation

Building automation describes the functionality provided by the control system of a building. A building automation system is an example of a distributed control system...

and lighting control solutions are now available to help reduce energy usage and cost by eliminating over-illumination. These solutions provide centralized control of all lighting within a home or commercial building, allowing easy implementation of scheduling, occupancy control, daylight harvesting and more. Many systems also support demand response

Demand response

In electricity grids, demand response is similar to dynamic demand mechanisms to manage customer consumption of electricity in response to supply conditions, for example, having electricity customers reduce their consumption at critical times or in response to market prices...

and will automatically dim or turn off lights to take advantage of DR incentives and cost savings.

Many newer control systems are using wireless mesh open standards (such as ZigBee

ZigBee

ZigBee is a specification for a suite of high level communication protocols using small, low-power digital radios based on an IEEE 802 standard for personal area networks. Applications include wireless light switches, electrical meters with in-home-displays, and other consumer and industrial...

), which provides benefits including easier installation (no need to run control wires) and interoperability with other standards-based building control systems (e.g. security).

External links

Government of Hong Kong Health Effects of Lighting in the Workplace
International Energy Agency's Policies for Energy-efficient Lighting
Case study on interior lighting of optical stores, 16 June 2007, Friends of the Earth (Hong Kong)
Lighting levels recommended by the IES (multiply footcandles by 10.76 to convert to lux)

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Numerical definition

Related phenomena

Causes

Forsaking use of sunlight

Failure to use occupancy sensors

Failure to delamp or use available lighting controls

Headaches, fatigue, stress and performance effects

Circulatory and circadian rhythm effects

Energy and economic considerations

Building and lighting control systems

See also

External links