lighting types

High-intensity discharge

(HID, including primarily metal halide, high-pressure sodium, and low-pressure sodium)

Solid-state lighting

(SSL, also referred to as LED lighting) efficiency, controllability,durability.

Light-emitting diode(LED)

Induction lighting

High-efficiency, long-duration

Incandescent

Compact fluorescent

Linear fluorescent

Halogen

Mercury vapor

Metal halide

High-pressure sodium

Low-pressure sodium

Induction

Solid-state lighting

 

Lighting power density(LPD)

Is defined as the electric power consumed by lighting divided by the net floor area of a space in a building, in units of watts per square foot. For example, a 100 square foot office with two 4-lamp fluorescent fixtures, at 170 watts per fixture, has an LPD of 2*170/100=3.4 watts per square foot(W/SF).

 

Lighting power allowance(LPA)

A maximum allowable LPD is called a lighting power allowance. IEEC(international energy conservation code) 2015 set an LPA of 1.11W/SF for enclosed offices.

 

Illuminance

Illuminance (sometimes called illumination) is a measurement of light reaching a surface.

International system of measurement (SI) unites: lux

English units:foot-candles(FC)

1 lux=10.8 foot-candles

Illuminance is measured with a light meter. Required Illuminance depends on the use of a space. A space used for activities requires higher illuminance than spaces like corridors or stairwells. Illuminance measurements are used for energy work to access if existing light levels are too high, and so provide an indication of portential for energy conservation, as a check on LPD measurements.

Illuminance is the quantity of light or luminous flux falling an a unit area of a surface the unit of illuminance

Unit: Lumen/㎡ or Lux

 

Luminance of a light-emitting object or surface is the luminous intensity emitted per unit of (apparent) area of that surface in a specific direction

Unit: candela /㎡

 

Luminous efficacy

Luminous efficacy is a measure of the energy-efficiency of a particular light source, in laments per watt(Lu/W). Luminous efficacy is useful for comparing types of lighting. For example, a standard 60-watt incandescent screw-in lamp with a rated luminous flux of 840 laments, having a luminous efficacy of 840/60=14lm/W.

 

Color-rendering index(CRI)

Color-rendering index(CRI) is a measure of a light source’s ability to show colours realistically. Over 80 is regarded as good, 100 is regarded as ideal.

 

Correlated color temperature(CCT)

It is a property of lamps that is related to their colour appearance.

Unit: degrees kelvin(K)

CCTs below 3200K are regarded as warm light, and above 4000 are considered cool light.

 

Codes and standards

Codes and standards address lighting in two ways: minimum illuminance and minimum energy efficiency.

 

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“Field Guide.” Energy Audits and Improvements for Commercial Buildings. Hoboken, NJ, USA: John Wiley & Sons, Inc, 2016. 17–26. Web.