LIGHTING DESIGN: LECTURE - 4
Luminaires
Luminaire Literature: Cut sheet
Lighting calculations
LIGHTING DESIGN LECTURE 4
luminaires
Luminaire Components
Luminaires generally consist of some or all of the following parts:
1. Lamps and lamp holders or sockets
2. Ballasts to start and operate the lamps
3. Reflectors to direct the light
4. Shielding/diffusion components (lens, diffuser, louver, or the like)
to shield the lamps from the eyes at normal viewing angles,
reduce discomfort
disability glare, and to distribute light evenly
5. Housings to contain the above elements as well as electrical
components, such as wiring connections
An efficient luminaire optimizes the system performance of
each of its components.
LIGHTING DESIGN LECTURE 4
luminaires
Luminaire Performance
Luminaire efficiency is the ratio of lumens emitted by the luminaire
to lumens emitted by that luminaires lamps
System performance depends on how well all these components work
together
An efficient luminaire optimizes the system performance of
each of its components.
LIGHTING DESIGN LECTURE 4
luminaires
General Lighting Luminaire Types
Open Direct Luminaires
surface- and pendant mounted strip fluorescent
fixtures and suspended open industrial and commercial
luminaires.
Shielded Direct Lighting Systems
use some form of lens, louver, or baffle to prevent
direct viewing of the lamps at normal angles of view
Parabolic Louvered Recessed Troffers
specular parabolic louvers to control the luminaires
light distribution, providing sharp cut-off glare control
An efficient luminaire optimizes the system performance of
each of its components.
LIGHTING DESIGN LECTURE 4
luminaires
General Lighting Luminaire Types
Indirect Lighting Systems
Lighting systems that radiate light up to a
reflecting ceiling are called indirect lighting systems.
Cove Lighting System
Direct/Indirect Lighting Systems
combine the benefits of both traditional direct
lighting and indirect lighting systems.
An efficient luminaire optimizes the system performance of
each of its components.
LIGHTING DESIGN LECTURE 4
luminaires
Architectural Luminaire Types
Architectural lighting systems, which are generally used in building spaces
such as lobbies and corridors include recessed down lights, wall washers,
track lights, and wall sconces.
Decorative fixture concepts.
Track mounted
Canopy mounted for a quick interchanging
Table and Floor lamps for local light
Fixtures can be directional / diffused / self luminous (sparkle)
Low voltage sources require a transformer
LIGHTING DESIGN LECTURE 4
luminaires
LIGHTING DESIGN LECTURE 4
luminaires
LIGHTING DESIGN LECTURE 4
luminaires
LIGHTING DESIGN LECTURE 4
Luminaire Literature: Cut sheet
Gives an idea of what a fixture is all
about
Images
Dimensions and requirements
Show possibilities or options for a
lighting event
Make sure we get the exact
product we are after
Catalog numbers
Options and accessories
LIGHTING DESIGN LECTURE 4
Luminaire Literature: Cut sheet
Information on a cut sheet :
Physical basics
Fixture size, housing size,
profile, aperture size
Mounting requirements /
recess requirements
Aesthetics
Finish color
Trims, reflectors, diffusers
Accessories: baffles, louvers,
blades
LIGHTING DESIGN LECTURE 4
Luminaire Literature: Cut sheet
Light suitability
UL label, wet or damp listing, Ip rating
Getting electricity to the fixture
Adjustability
Glare, glare control
Dimming, switching, instant on/off
Lamp basics
Fixture lamp source options
Number of lamps
Lamp shape/length, lamp mounting (socket)
Fixture voltage options (120, 240 etc.)
Fixture wattage max (heat concerns)
Ballast or transformer requirements
LIGHTING DESIGN LECTURE 4
Luminaire Literature: Cut sheet
Light output /
performance
Lumen output
Efficiency / efficacy
Distribution shape
Photometric report
Photometric distribution
diagram shape
Spot, flood, wash,
spread, accent, smooth,
asymmetric, asymmetric,
Candela values in
specific directions
LIGHTING DESIGN Lecture 4
Lighting For Tasks
The IES: Illuminating Engineering Society. The governing body of
lighting engineering
IES associates tasks with specific light levels (Illuminance)
IN LUMENS PER
SQUARE METER/LUX
METER (LEAVING)
All measures of light boil down to density: Lumens per area.
LIGHTING DESIGN Lecture 4
Lighting For Tasks
Recognize that Illuminance is light ON TO a surface
Units: lumens per square meter/ Lux
Does not tell us about:
the appearance of the surface being lighted
Nor the perceived brightness of a space
So why are lighting criteria of IES based on Illuminance?
concerned with lighting for specific tasks
Vision is based on contrast
Tasks are assumed to be of materials of known reflectance, then
Known reflectance known contrast known visual performance
(old) IES considerations that affect criteria
Age of participants
Time allowed for task
Importance of task
Reflectance of surroundings
Proper task illuminance does not automatically mean a
successful or bright environment.
LIGHTING DESIGN Lecture 4
Lighting For Tasks
Dont rely on Illuminance level recommendations that arent relevant
to your space.
Remember: we are talking about the fifth and last layer
Get used to
Full moon moonlight: 1Lux
Movie theater walk way 10 Lux
(minimum for emergency exit)
Dim romantic restaurant 50 Lux
Comfortable living room 100-150 Lux
Residential task / study 200-350 Lux
Classroom/ small office 500-700 Lux
Excessively bright open office 700-850 Lux
1000+ Lux very bright for an interior space
2000+ Lux unheard of for an average E level in interior
Remember: these are not recommendations. Rather, they are
estimates of what you may be visualizing for each example.
Learn to intuitively describe a space in terms of a perceived
ambient illuminance level.
Lighting calculations
LIGHTING DESIGN Lecture 4
Lighting Calculations
Why:
Predict what lighting equipment will be
needed
Predict how a lighting system will perform.
Two ways in which we consider light
Lumen: Measured light flux output from a
source in an arbitrary direction
Candela: Light intensity in a specific
direction from a source
A Light source has one lumen output value,
but can emit different candela values in every
direction.
We get light output info from fixture cut
sheets / diagrams
Total lumen output
Candela distribution / diagram
Lumen output is the sum of all of the light leaving a light
source in every direction.
LIGHTING DESIGN Lecture 4
Lighting Calculations
The lumen method: calculating average Illuminance
Average value of Lumens distributed evenly over surface
Used for surfaces in large, simple, open areas with simple
layouts
Yields Illuminance, which is light ONTO a surface.
only intended to tell you about a specific surface
That surface can however be the entire floor, or an imaginary
task plane in a room.
Based on the unit definition of a Lumen per meter square
1 LUX = 1 lumen / meter square.
Illuminance = lumens / area
=> Lumens = Illuminance x area
LIGHTING DESIGN Lecture 4
Lighting Calculations
The Lumen method procedure:
Solving for lighting needs (determine how much light is
needed then how many fixtures are needed)
Determine area receiving light (usually task surface, floor or
work plane)
Define the desired Illuminance (in LUX)
Lumens needed = Area of space x Illuminance
Translates Lumens Needed into how many fixtures are
needed
Number of fixtures needed = lumens needed / (lumens per fixture)
OR.
If things get messy: lumens per fixture can be:
Number of lumens per lamp x Number of lamps per fixture
LIGHTING DESIGN Lecture 4
Lighting Calculations
Most architectural fixture cut sheets will list the total lumen
output in the 0-90 degree zone.
LIGHTING DESIGN Lecture 4
Lighting Calculations
The two safety factors make the Lumen Method procedure
more accurate.
1. Coefficient of utilization CU
How well the surface you are considering is receiving light
Room geometry, fixture orientation (uplight, downlight,
indirect, etc.)
Sample CUs to get used to
Direct fixture: 85% (0.85 in your equation)
Indirect fixture: 50% (0.50)
Spot / accent: 95% (0.95)
Wash / ambient: 75% (0.75)
2. Light Loss Factor LLF
Accounts for depreciation of lighting system over time
Lamp Lumen depreciation (LLD), lamp dirt depreciation (LDD),
ballast factor (BF)
LIGHTING DESIGN Lecture 4
Lighting Calculations
We generally make a safe assumption of LLF 85% (0.85)
Both of these factors have a huge impact on predicted effect of your
light solution.
So our lumen method equations become:
Illuminance = (lumens per fixture x No of fixtures x CU x LLF) / Area
Lumens needed = (Illuminance x area) / (CU x LLF)
Or describe your solutions in Functional Lumens
LIGHTING DESIGN LECTURE 04
Lighting Calculations
The point calculation method (using candela
values):
Candela output is an expression of the intensity of
a light source in a specific direction.
The Point Calculation accounts for this intensity
as it is affected by distance
Generally used for a specific surface lighted from a
specific distance by a directional / accent fixture
since candela is equal to lumen output divided by
spatial extent (steradian)
Illuminance = candela value / distance squared
E = CD / D2
1 candela is light intensity leaving a source in a density of one
lumen of light per steradian of spherical area
LIGHTING DESIGN Lecture 4
Lighting Calculations
The point calculation method procedure:
Define distance form light source to surface receiving light
(estimate)
Use elevations or trigonometry if necessary
Identify candela value of fixture in the appropriate direction
(we almost always use the center beam candle power (CBCP)
because it is the brightest)
CBCP of lamp from lamp catalog (if it is a lamp driven fixture)
Candela value from candela distribution (photometric curve) on
fixture cut sheet.
LIGHTING DESIGN Lecture 4
Lighting Calculations
Examples of locating candela values on cut sheets. We are usually
interested in the Center Beam Candela Value or CBCP.
LIGHTING DESIGN LECTURE 4
Luminaire Literature: Cut sheet
Assignment
Select a luminaries that fit your purpose and analyze
its cut sheet, and report on the following features for
each luminaries:
Basic fixture description
Fixture mounting type
Fixture source (lamp)
Fixture size, profile, shape
Fixture wattages available
Fixture voltages available
Ballast, transformer requirements
Is the fixture dimmable?
Is the fixture adjustable?
What optical control accessories are available?
Describe the photometric distribution (accent, wash, etc.)?
Can you determine the lumen output?
Can you determine the fixture efficiency?
Where would you use this fixture?
