Chapter 12: LIGHT SOURCES
Summary
This chapter considers characteristics and typical applications of all commonly encountered light sources
used in buildings. Daylight and electric light sources are included. The authors note that lighting
accounts for a substantial portion of electricity use in non-residential buildings and that attempts to reduce
such consumption will need to address daylighting and the efficacy of electric sources.
The nature of daylight as a light source for buildings is discussed. Factors affecting daylight availability
are considered. Four basic sky conditions (fully overcast, clear—with and without sun, and partly cloudy)
are presented and reviewed. The nature of these sky types as light sources is addressed along with a
comparison of their differences. Sample data to quantify daylight source potential are provided.
Electric light sources (lamps) are presented in detail. Major lamp families (incandescent and electric
discharge) are identified and commonly used lamps within each of these families are described and their
characteristics reviewed. For each lamp type, information is provided on principles of operation, physical
characteristics, and operating performance. Advantages and disadvantages of each lamp type with
respect to efficacy, illuminant quality, installation, and control capabilities are considered. Generic
performance data are provided for each lamp type.
Incandescent lamps include conventional filament lamps (in a wide range of options) and tungstenhalogen lamps. Electric discharge lamps include fluorescent (preheat, rapid-start, instant-start, compact,
and special), mercury vapor, metal halide, and high-pressure and low-pressure sodium. Ballast types,
characteristics, ratings, and applications are discussed, with emphasis on basic functions and ballast
control capabilities. Each lamp type is addressed in detail, including development, typical uses, cautions,
and appropriateness to common functions. Emerging inductance, light emitting diode, and sulfur lamp
technologies are presented. Fiber optics is briefly touched upon.
Chapter Outline
12.1 Basic Characteristics of Light Sources
12.2 Selecting an Appropriate Light Source
DAYLIGHT SOURCES
12.3 Characteristics of Daylight
12.4 Overcast Sky
12.5 Clear Sky
(a) Horizontal illuminance
(b) Vertical surface illuminance
12.6 Partly Cloudy Sky
ELECTRIC LIGHT SOURCES
Incandescent Lamps
12.7 The Incandescent Filament Lamp
(a) Construction
(b) Operating characteristics
(c) Other characteristics
(d) Summary
12.8 Special Incandescent Lamps
(a) Reflector lamps
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(b) Energy-saving lamps
12.9 Tungsten-Halogen (Quartz-Iodine) Lamps
12.10 Tungsten-Halogen Lamp Types
(a) Encapsulated lamps
(b) MR-16 Precision Reflector Units
Gaseous Discharge Lamps
12.11 Ballasts
(a) Ballast characteristics
(b) Ballast types
(c) Ballast performance
Fluorescent Lamps
12.12 Fluorescent Lamp Construction
(a) Preheat lamps
(b) Rapid-start lamps
(c) Instant-start fluorescent lamps
12.13 Fluorescent Lamp Labels
12.14 Fluorescent Lamp Types
12.15 Characteristics of Fluorescent Lamp Operation
(a) Efficacy
(b) Lumen maintenance
(c) Lamp life
(d) Effect of temperature and humidity
(e) Dimming
12.16 Federal Standards for Fluorescent Lamps
12.17 Special Fluorescent Lamps
(a) Low-energy lamps
(b) U-shaped lamps
(c) Ecologically friendly lamps
(d) UV lamps
12.18 Compact Fluorescent Lamps
HIGH-INTENSITY DISCHARGE LAMPS
12.19 Mercury Vapor Lamps
(a) UV radiation
(b) Lamp life
(c) Lumen maintenance
(d) Color correction and efficacy
(e) Ballasts and lamp starting
(f) Self-ballasted lamps
(g) Application
12.20 Metal Halide Lamps
(a) Lamp configurations
(b) Safety
(c) Designs, shapes, and ratings
(d) Operating characteristics
(e) Lamp ballasts
12.21 Sodium Vapor Lamps
(a) Primary characteristics of HPS lamps
(b) Other operating characteristics
(c) Lamp design types
12.22 Low-Pressure Sodium Lamps
OTHER ELECTRIC LAMPS
12.23 Induction Lamps
12.24 Light-Emitting Diodes
12.25 Sulfur Lamps
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12.26 Fiber Optics
References
Key Concepts
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luminous efficacy (as a measure of the efficiency of a light source)
daylighting (as a design method and an intent)
the nature of outdoor illumination (as a means of understanding this as a light source)
design sky conditions (as a design resource and system component)
electric lamp (as a class of light sources and system component)
incandescent lamp (as a common electric lamp type)
electric discharge lamp (as a family of common lamp types)
ballast (as an operational and control device)
life-cycle cost analysis (as a decision-making tool)
Terminology and Metrics
Important Terminology
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IESNA (Illuminating Engineering Society of North America)
CIE (Commission Internationale de l=Eclairage)
Energy Policy Act (EPACT)
luminous efficacy (efficiency)
daylighting
altitude angle
azimuth angle
bearing angle (or solar window azimuth)
sky conditions
solid overcast sky (CIE sky)
clear sky, without sun
clear sky, with sun
partly cloudy sky
horizontal illumination
vertical surface illumination
lamp
incandescent lamp
general service
tungsten-halogen (quartz-iodine)
encapsulated lamp
MR-16 precision reflector lamp
rough service
vibration
extended-service
reflector lamp
energy-saving lamp
filament
incandesce
life-cycle cost analysis
spectral content
initial lumens
mean (or design) lumens
lumen maintenance
solid-state thyristor dimmer (SCR, triac)
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dimming
partial dimming
full-range dimming
output reduction
ballast
magnetic ballast (magnetic core-and-coil, EM)
electronic ballast (EL)
power factor corrected (high power factor) ballast
dimming ballast
multi-level ballast
energy saving ballast
ballast factor (BF)
ballast efficacy (or efficiency) factor (BEF)
radio frequency interference (RFI)
electric (gaseous) discharge lamp
fluorescent lamp
preheat lamp
rapid-start (RS) lamp
standard-output lamp
high-output lamp
very-high-output lamp
instant-start lamp
low-energy lamp
triphosphor lamp
T8 lamp
T5 lamp
compact fluorescent lamp (CFL)
high-intensity discharge (HID) lamp
mercury vapor
metal-halide
high-pressure sodium lamp (HPS or SON)
non-cycling lamp
standby lamp
retrofit lamp
low-pressure sodium lamp (SOX)
self-extinguishing lamp
safety-shielded lamp
induction lamp
light emitting diode (LED)
sulfur lamp
fiber optics
Important Metrics
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lm/W (lumen per watt, luminous efficacy)
BF (ballast factor, as a percentage)
BEF (ballast efficacy factor, as a numeral)
Links to Resources
General Electric (lighting):
http://www.gelighting.com/na/
Osram Sylvania (lighting):
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http://www.sylvania.com/
Philips Lighting:
http://www.lighting.philips.com/
Federal Energy Management Program (energy efficient fluorescent ballasts):
http://www.eere.energy.gov/femp/technologies/eep_fluor_ballast.cfm
U.S. Environmental Protection Agency, Energy Star-Labeled Lamps and Luminaires:
http://www.energystar.gov/index.cfm?c=lighting.pr_lighting
U.S. Department of Energy High Performance Buildings Program:
http://ww.eere.energy.gov/buildings/highperformance/
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