Lighting Flashcards
Emergency lighting in means-of-egress areas must have an intensity of no less than ______ fc (Fill in the Blank)
Building codes require a minimum of 1 fc at the floor level of areas that serve as means of egress. For assembly occupancies, such as an auditorium or theater, the level may reduced to 0.2 fc during performances, but must be automatically restored to 1 fc upon activation of the buildings fire alarm system. Exceptions to the minimum include U, guest rooms in group R-1, dwelling rooms, and sleeping rooms in Groupds R-2 and R-3 occupancies. Sleeping rooms in Group 1 occ are also exempt.
How are ballasts rated for sound?
A=quiet; F=noisy
A _________ is used to turn on and off to regulate the flow at intermediate rates. Even when wide open, the flow is somewhat restricted. a. Globe Valve b. Gate valve c. Angle valve d. Check valve
a. Globe Valve
What are veiling reflections/reflected glare?
Light sources that can be seen on a surface. They involve task and light source.
What is the difference between illuminance and luminance?
Illuminannce = E (In); Luminance = L (Leaving) Illuminance measured in fc Luminance measured in footlambert
Candlepower is analogous to what in the electrical and hydraulic systems?
Cp are alanogous to voltage (electrical) or pressure (hydraulic)
Lumens are analogous to what in the electrical and hydraulic systems?
Lumens are analogous to amperes (electrical) or flow (hydraulic)
What is the thing is measured in photometric power? What is photometric power?
Lumens are a measure of photometric power, meaning it is perceived by the human eye as a function of physiology
What agency has worked to rationalize lighting design?
Illuminating Engineering Society of North America
What is the color rendering index (CRI)? How is it measured?
Measured how closely the perceived colors of an object illuminated with daylight of the same color temp. Max CRI is 100 so a rating of 85 is good
What is max lux for energy budget?
2.3 W/sq ft
Describe Low Pressure sodium lighting.
Up to 150 lm/W, produces yellow light, used for street lighting
High Pressure Sodium (HPS)
80 – 140 lm/W, uses Hot sodium Vapor
What are the primary advantages of incandescent lamps?
- low cost 2. instant start and restart 3. simple, inexpensive dimming 4. simple, compact installation 5. cheap fixtures 6. focusability as a point sorce 7. high power factor 8. lamp life independent of number of starts 9. skin flattering, full spectrum color
What are the primary disadvantages of incandescent lamps?
- low efficacy 2. short lamp life 3. critical voltage sensitivity
Because of its poor energy characteristics incandescent lamps should be limited to what application?
- where use is infrequent 2. where there is frequent short duration use 3. where low cost dimming is required 4. where minimum initial cost is required 5. where good color rendering is required
What shapes are reflector lamps made in?
R, BR, ER, PAR
What are the advantages of reflector lamps?
accurate beam control narrow=spot wide=flood
Which os the following would NOT maximaize daylighting while minimizing solar heat load? A. horizontal shades B. light shelves C. tinted glass D. building shape
C. tinted glass Although tintied glass would reduce the heat load, it would not be good for maximizing daylighting. Low e glass or super windows with clear glazing would be more appropriate. All other choices would be good ways to minimize direct sunlight on the glass while improving transmitted light to the interior of the building
The angle of the sun’s orientation relative to due south is called A. altitude B. azimuth C. declination D. Solar angle
B. azimuth
What is sun declination?
The angle of the north south axis of the earth relative to the sun. It’s what causes seasons to happen throughout the year.
How are fluorescent lamps designated?
Type,wattage,diameter,color,method of starting
What is efficacy? How is it measured
The ratio of luminous flux emitted to the toal power input tot eh source; measured in lumens per watt
A footlambert is is the unit of….?
luminance
Luminance is the luminous flux per unit of projected area and unit solid angle leaving a surface, either reflected or transmitted.
Luminance takes into account…
the reflectance and transmittance properties of materials and the directions from which they are viewed.
How is luminance calculated?
It’s calculated by multiplying the reflectance of material times the illluminance.
Whichof the following types of lamps provides the best color rendition of skin tones?
A. cool white flourescent
B. incandescent
C. mercury vapor
D. metal halide
indandescents
An incandescent has a high color rendering index (CRI) and a low color temperature, with a predominance of light in the red range.
A cool white flourescent lamp has more blue and green light and its spectral distribution makes skin tones appear more gray and washed out. oth mercury vapor and metal halide lamps have poor color rendering indexes and are not appropriate for lighting areas where skin tone rendition is important.
The zonal cavity method of calculating average illumination on the work surface for a given number of luminaires depends on which of the following variable? (choose 4)
A. angle of light
B. dirt accumulation
C. efficacy of the lamp
D. lumens per lamp
E. room size
F. wall reflectance
B. dirt accumulation
D. lumens per lamp
E. room size
F. wall reflectance
THe zonal cavity method is used to calculate the total number of luminaires required to achieve the desired average illumination on the work surface, which is asusmed to be 30 in above the floor. The variables considered in the calculation include the level of illumination desired, the area of the room, the number of lamps in wach luminaire, the lumen output of each lamp, the coefficient of utilization, the light loss factor (LLF) wall reflectance, and the gradual loss of light due to dirt accumulation.
What is the zonal caivty method used for?
It’s used to calculate the total number of luminaires required to achieve the desired averageillumination on the work surface, which is assumed to be 30 inches AFF.
What are the variables considered in calculating the zonal cavity method?
- level of illumination desired
- the area of the room
- the number of lamps in each luminaire
- the lumen output of each lamp
- the coefficient of utilization
- light loss factor
- wall reflectance
- and teh gradual loss of light due to dirt
What is the coefficient of utilization?
CU is a measure of the efficiency of a particular luminaire in outputting light and is based on the design of the luminaire itself, the reflectance of the room, and size of the room.
What is light loss factor?
LLF represents a degredation of ideal light output due to aging of the lamp and gradual dirt accumulation on the lamp.
Problems with veiling reflections in a general purpose workroom could best be reduced by
A. substituting ambient light for direct light fixtures
B. repositioning the light fixtures
C. reducing the brightness of the light fixtures
D. changing the type of lamps
A. substituting ambient light for direct light fixtures
A veiling reflection is glare caused when the image of a light source is relfected from a viewing surface into the eye. The best way to reduce it is to provide general background illumination (ambient lighting) so the light sources are not concentrated in the area of the lamp.
Repositining the luminaires (or the task) can reduce veiling reflections, but only when the task is in a specific location in relation to the light source. In a general purpose workroom this would not be feasible. Reducing the brightness of the light source would help, but would also reduce the illumination provided for the task. Chaning the type of lamps would have little effect on reflected glare.
Variable that must be considered when designing for daylighting include all of the following EXCEPT
A. glass transmittance
B. height of the head of the glass
C. longitude of the site
D. outdoor surfacereflection
C. longitude of the site
The longitude of the site is not a factor in daylighting design. The latitude of the site might have a minor influence on how a daylighting design is implemented, but this is not a critical variable.
Variables that affect daylighting include the brightness of the sky (which is affected by solar altitude, cloud conditions, and time of day), the area of glass, the height of the head of glass, the transmittance of the glass, the reflectance of surfaces within the rooms and nearby outdoor surfaces, and obstructions such as overhangs and trees.
What are the variables that affect daylighting?
- the brightness of the sky (which is affected by solar altitude, cloud conditions, and time of day)
- the area of glass, the height of the head of glass
- the transmittance of the glass
- the reflectance of surfaces within the rooms and nearby outdoor surfaces
- obstructions such as overhangs and trees.
For a room with a standard window whose head is 8 ft above the floor, daylighting could be used for illumination for a distance from teh window of approximately…
12 ft
For a window with no light shelf, daylighting is effective for a distance of about 1.5 times the head height of the window. Wiht a light shelf, the effective distance increases to about 2.0 to 2.5 times the head height.
What combination of lighting would by the most appropriate choice for a women’s clothing store?
A. color improved mercury lamps with metal halide accent lighitng
B. limited natural daylight, warm white deluxe flourescent for general illumination, and tungsten halogen for accent lighting
C. incandescent general lighting with low-voltage accent lighting on displays
D. daylighting for general illumination and incandescent fixtures for dressing areas and display lighting
The combination of limited natural light, warm white flourescent general illlumination, and tungsten halogen accent lighting offers the best balance of appropriate color rendering and energy efficiency. Daylighting would provide natural light for viewing clothes and excellent color renderings, but wold need to be limited in order to prevent damage to delicate fabrics. Warm white deluxe lamps would be energy efficient and provide a pleasant, overall light. The tungsten halogen accent lights will provide sparkle to jewlry displays and highlight featured merchandise.
Mercury lamps and metal halide lighting have cooler tones which may render colors inapporpriately. Incandescent fixtures throughout would not be energy efficient. Using daylighting for general illumination could damage fabrics and would limit the stores hours of operation to daylight hours.
Which of the following would an architect be most concerned when designing the lighting for an office space with computer workstations and standard desks.
I. color rendering index
II. visual comfort probablity
III. veiling reflections
IV. reflected glare
V. tasks.surround brightness ratio
III. veiling reflections
IV. reflected glare
V. tasks.surround brightness ratio
In a standard office space where video display tubes (VDTs) and standard office tasks are present, the architect should be concerned with two results of glare. Veiling reflections would be of a concern for standard office tasks such as writign and reading, whereas reflected glare woulf be critical in using the VDTs. The brightness ratios between the tasks and their surroundings are important, especially with VDTs. The color rendering index and visual comfort probablity are less important.
An architect wants to increase the expected lighting level of a room. Which of the following steps could accomplish this?
A. Change to a lamp type with a lower efficacy
B. suggest tot he owner that the lamps be replaced infrequently
C. Use finsihes with a lower reflectance
D. Change to luminaires with a higher coefficient of utlitzation
D. Change to luminaires with a higher coefficient of utlitzation
Luminaires with a higher CU allow more light from teh lamps to reach the desired surfaces. Lamps with a hgiher efficiency, not lower, shoulf be selected, althoguh this would have to be balanced against the change in color temperature. Lumen output decreases as lamps age and as dirt accumulates on them. Chaning lamps often would help maintain initial footcanlde level. Room finishes with high reflectance can make a significant increase in the total light level in a room.
Glass that changes darkness in response to a change in the level of daylight is…?
photochromatic
Which of the following units would be used to measure the brightness of daylight coming through a window?
A. footcandle
B. candela
C. footlambert
D. candlepower
C. footlambert
Footlambert is the unit of measure of the brightness (or luminance) of a surface and takes into account the transmittance properties of the glass. Footcandle is the unit of measure of the light incident on a transmiting or relfecting surface. Candela is the SI unit for candlepower, which is a measure of luminous intensity.
Why would high-pressure sodium lamps be favored over low-pressure sodium lamps in a storage warehouse?
They have better color rendering properties.
Low pressure sodium lamps produce a monochromatic yellow light that would not be appropriate in a storage warehouse where people ma have to discriminate between colors.
An architect is designing an art school at a major university. Which combination of daylighting and electric lighting would be the most appropriate choice for the painting studios?
A south facing windows and incandescent recessed lights
B. north facing windows and skylights and fixtures with high CRI flourescent lamps
C. windows to teh eat and west and flourescent fixtures in coves at the perimieter of teh studio
D. north facing skylights nd metal halide lamps at each workstation
B. north facing windows and skylights and fixtures with high CRI flourescent lamps
Adding white to a color pigment results in a
tint
What is tint?
Adding white to a color pigment, making it lighter
Adding black to a color pigment results in a ….?
shade
What is value in color pgiment?
Characteristic of a pigment that describes its lightness or darkness.
what is hue?
it defines a color–red, blue, yellow, and so on
What is chroma?
defines a color’s saturation
A footlambert is a measure of
Luminance
Luminance is the luminous flux per unit of projected area and unit solid angle leaving a surface, either reflected or transmitted. Luminance takes into account the reflectance and transmittance properties of materials and the directions from which they are viewed. Luminance is sometimes mistakenly called brightness. Luminance is calculated by multplying the reflectance of materials time the illuminance (measued in footcandles or lux)
Light:
electromagnetic radiation wavelength seen by the human eye
incident Light:
the direct light that falls on a surface
Transmitted:
light that passes through a surface…all other is reflected or absorbed
Transparent:
material that allows for an image to pass through (glass)
Refraction:
material that changes an image while allowing it to pass through (lens)
Translucent:
material that allows light to pass through, but not an image (frosted glass)
Reflective:
material that bounces a light off
Opaque:
material that reflects or absorbs all light
Coefficient of Transmission:
the ratio of the total transmitted light to the total incident
light represented as a percentage
Reflectance Coefficient:
the ratio of total reflected light to total incident light expressed
as a percentage
Reflection:
light bouncing off a material
Specular Reflection:
results from a smooth polishes
surface like a mirror. The angle of incidence equals the
angle of reflection
Diffuse Reflection:
results from a uniformly rough
surface. It appears uniformly birth and the image of
the source cannot be seen.
Combined Specular:
makes surface appear to be
brighter at the oping where the source is shining than
in surrounding areas
Photometry:
the measurement of light in terms of
perceived brightness to the human eye
Intensity (I):
the amount of light put out by a source
Candlepower (CP):
the measurement for the intensity
of a source, and approximately equal to the horizontal
output from a single candle
Lumen (I):
SI unit of luminous flux, a measure of the total amount of visible light emitted by a source. One lumen of luminous flux uniformly cast on 1 square foot of area creates an illuminate of 1 foot candle
Flux (F):
the flow of light from a source into space
Illumination (E):
the amount of light arriving at a surface
Footcandle (FC):
the calculated amount of illumination on a surface
Luminance:
the measurement of how bright light leaving an illuminated surface is…it
depends on reflectivity or transmittance.
Illuminance:
the density of luminous energy expressed as lumens per unit area
Lambert:
unit of luminance or brightness
Coefficient of Utilization (CU):
ratio between lumens reaching the working plane in a
specific space and the lumens. Typically provided by the luminaire manufacturer, it’s an
indication of the effectiveness of a luminaire in delivering light in a given space
Luminaire Efficacy Rating (LER):
ratio of fixture lumen output per wall of lamp input
Light Loss Factor (LLF):
effect of temperature and voltage variations, dirt accumulation
on luminaries and room surfaces, lamp output depreciation, maintenance conditions.
Efficacy:
the amount of light produced vs. the power input (lumens/watt)
Contrast:
Difference in illumination level between one point and nearby points.
Equivalent spherical illumination (ESI):
theoretical sphere surrounding an object being
illuminated with light, cast evenly and eliminating any shadows and reflected bright spots
Spectral Energy Distribution:
measure of energy output at different wavelengths/colors
Color Rendering Index (CRI):
a measure of the effectiveness of a source to make
colors “right” to the viewer. The best possible rating is 100. 85 + is good.
Color Temperature (K):
a characteristic of visible light where its color reveals it temp.
• Parts of the Eye
Cornea: Covers the iris/pupil/chamber
• Lens: Focusing Device
• Iris: Controls the amount of brightness admitted
- Retina: Sensing Device
- Cones: Sense Color
- Rods: Sense Black and White
Electromagnetic (EM) Spectrum and Visible Light
Visible Light has a wavelength of about 380 - 740 nanometers
• The dormant wavelength determines the perceived color
• Higher frequencies have shorter wavelengths
• Lower frequencies have longer wavelengths
• At the lower end of the visible light spectrum, EM becomes invisible to
humans…known as infrared
• At the higher range of the visible light spectrum, ultraviolet light becomes invisible
because it is absorbed the tissues of the eye. Rods and cones can’t detect the short wavelengths
Good lighting aims to:
Reinforce the functionality of the spaces
• Add to the acceptability/appreciation of space by the occupant. • Add value to the project
• Create a feature that assists in the sale/rental of a space
• Promote worker productivity and/or merchandise sales
• Reduce long-term expenses
• Minimize customer/user satisfaction
Orientation is influenced by lighting needs:
• Place important spaces and windows at southeast corner of the site, it will get more
sun in the winter and less in the summer
• Place windows on the south side to get winter sun into the space
• Use architectural overhangs/fins/louvers and to some extent deciduous vegetation to
block solar rays in the summer
Use few windows on the east and west sides of buildings because of morning and late afternoon sun.
If unavoidable, use vertical fins to block solar rays.
Use northern windows for even daylight throughout the day.
Measuring Light
• Photometric readings are usually taken at the height of a “working plane” because this
approximates the height to typical visual tasks
• Illuminance is measured more frequently than luminance because design
recommendations for lighting levels are typically given in terms of illuminance
Selection criteria when picking a lighting fixture (from most important to least):
- Color Rendition
- Characteristic of the fixture
- Initial Cost
- Operating Cost
- Efficacy
- Size
- Heat Output
- Operating Life
- Ability to control output from luminary
Permanent Supplementary Artificial Lighting of Interiors (PSALI):
- Natural light is more pleasant to work in than artificial light, but sometime the amount of natural light provided varies during the day, and the illumination levels vary within a room.
- Combining daylight and artificial light is a good way to compromise by blending the two together to provide even illumination
- Retains most of the psychological advantages of natural lighting but can illuminate deeper into rooms than daylight could alone
- Lamps used in fixtures should match natural light color
• Point Grid Method:
- A method of calculating illumination (E) for surfaces not perpendicular to the source • Good for a single fixture or small number of fixtures
- Takes into account orientation and distance but ignores surrounding reflection
• Zonal Cavity Method:
- Used to calculate uniform illuminance in a space, based on a uniform distribution of a large number of fixtures
- Takes into account the reflectivity of the ceiling and walls and the comparative volumes of the top, middle, and bottom of the room.
- Space is divided into: Ceiling Cavity, Floor Cavity, and Room Cavity
- Most commonly used for office, commercial and factory spaces
- Based on the Coefficient of Utilization (CU) for each fixture type
Lamp Lumen Deprecation (LLD):
the overall performance of a lamp over its life,
typically given in manufacture data
Ballast Factor (BF):
compares the ratio of light output of a lamp working by a specific ballast to the light output of the same lamp working by a standard reference ballast.
Luminaire Dirt Deprecation (LDD):
the light loss prior to cleaning dust
Room Surface Dirt Depreciation (RSDD):
accounts for dirt or dust that
accumulates on all of the room surfaces especially on the upper walls and ceiling
Glare:
extreme contrast in light (difference in brightness levels)
Direct Glare:
a light source in the field of vision that causes interference/distraction with
a visual task
Critical Glare:
zone for direct glare is the area above a 45° angle from the light source
Reflective Glare:
when a light source is reflected from a viewing surface into the eye
and interferes with a viewing task
Discomfort Glare:
annoying pain caused by high luminances in a field of view (most
common cause are windows and luminaries)
Veiling Reflection:
reflection which partially or totally obscure the details to be seen by
reducing the contrast. A common problem with specular surfaces.
Visual Comfort Probability (VCP):
a rating that indicates the percentage of people that
will find a given discomfort glare acceptable. 70% is the minimum, else it’s time to fix it.
Quantitative Lighting Issues
- Daylight and how it is introduce and integrated with electric light
- Interrelationship between energy aspects of electric and natural lighting and HVAC
- Effect of lighting on interior space arrangement and vice versa
- Characteristics, means of generation, and utilization techniques of electric lighting
- Visual needs of specific occupants and of specific tasks
Qualitative Lighting Issues
- Location, interrelationship, and psychological effect of light and shadow
- Use of color, both of light and surface faces, and the effect of illuminant source on object color or vice versa
- Artistic effects possible with patterns of light and shadow
- Physiological and psychological effects of lighting design, particularly in spaces occupied for extend periods
Efficacy:
the amount of light produce vs the power input (lumens/watt)
Daylight Factor (DF):
ratio of indoor illuminance to available outdoor illuminance
Externally Reflected Component (ERC):
the light reflected from exterior obstruction
excluding the ground reflected light
Effective Aperture (EA):
product of visible transmittance multiplied by the window to
wall ratio. An EA of .20 - .30 provides good daylighting
Energy Policy Act (EPACT):
set minimum standards for energy efficiency on incandescent and fluorescent lighting
Graphic Daylighting Design Method (GDDM):
daylighting analysis method that produces a family of daylight factor contours within a room rather than individual daylight factors at specific points
Lamp:
a device for giving light
Luminare:
a complete light fixture including lamps
Light Shelf:
overhang that’s exterior, interior, or both, used with a clearstory to reflect
light up on to the ceiling and reduce direct light adjacent to the window
DaylightFactor =
0.2x(windowarea/floorarea)
Effective Daylight Zone =
- 5 x (window head height into room)
- 0 x (window head height into room w/light shelf)
Workplane Daylight Illuminance =
2.5 x the head height of the window (height of the window above the desk plane)
Bilateral Light:
light coming from two sides to illuminate a space (it’s a good thing)
In general, daylight will penetrate further into a space and have a more uniform quality if windows are placed high on the wall
Controlling Daylight with architecture:
• Overhangs, fins, and other architectural shading devices.
• Sawtooth (not bubble) skylights allow glass to face north for illumination, not south
for solar heat gain. DO NOT USE BUBBLE SKYLIGHTS.
• Interior window shading devices, which allow solar gain during cool months, and
the blocking of solar radiation during the warmer seasons.
• Light shelves, which permit the daylight to reflect off the ceiling and penetrate
farther into the interior without affecting views outside.
A - Appliance
- Most Common
- Used Almost Everywhere
PS - Pear Shape
• Similar to “A” but have a larger diameter • Used in offices, retail
• Used in radio/cell tower, bridge power
line, high tension wires
S - Sign
- Found in outdoor signs
- Casinos, hotels, theaters
C - Candle
- Made to look like candle flame for decorative applications
- Used in chandeliers, restaurants, bathrooms, decorative lights
- Rounded blunt tip is called “torpedo shaped” (think xmas lights)
F - Flame
- Similar to “C” but glass is blown or etched so light looks like it’s flickering through a flame
- Used in decorative applications
G - Globe
• Found in decorative applications like bathrooms and lobbies
R - Reflector
- Built in reflecting surface which causes light to pushed through front of bulb instead of emitting around the entire bulb
- Used for downlighting
- Used in can or track lighting
BR - Bulk Reflector
- Created in response to EPACT which requires reflector bulbs to meet minimum standards
- Bulk reflector in neck of bulb redirects lost light forward
- Used for downlighting
ER - Elliptical Reflector
• Also create in response to EPACT
• Elliptical reflector increase the overall
lumen output by redirecting lost light at
the sides forward
• Used for downlighting
PAR - Parabolic Aluminized Reflector
- Have an aluminized reflector in a parabola shape
- Covered with a hard glass relines to control light beam
- Use unprotected outdoors because glass can withstand weather
- Used for downlighting
MR - Mirror Reflector
- Have a mirrored reflector
- Used for accent and stop lighting
T - Tube
• Shaped like cylinder tube
• Can be Incandescent, Fluorescent, or
HID
• Used for everything
Tungsten Halogen
• A variation of incandescent bulbs. A filament is lit by electricity passing through
an enclosed in sealed bulb containing an inert gas and halogen
• Smaller than standard incandescent bulbs
• Filament burns under higher pressure and temperature
• Uses a fuzed quartz envelope that allows for the higher temp
• A chemical reaction takes place pulling the tungsten from the wall of the glass
and back to the filament, extending its life
Advantages of Tungsten Halogen
- Longer life
- Low lumen deprecation of the life of the bulb • More uniform light color
- Whiter light than incandescent
- Dimmable
DisadvantagesTungsten Halogen
• Much hotter than incandescent bulbs
Fluorescent Lights
• A glass tube holds a mixture of an inert gas and low pressure mercury vapor
• When lamp is energized, an arc of mercury is formed creating an ultraviolet light
that strikes the phosphor coated bulb
• Bulb fluoresces and produce a visible light
• Pre Heat: supplanted by rapid start that maintains constant low current in the
cathode, allowing them to start within 2 seconds
• Instant Start: use a higher voltage to illuminate immediate
• Ballast: supplies the proper starting and operating voltages to the lamp and
limits the current
• Produces noise and heat so, “Class A” is good for quit areas and “Class F” is
acceptable for noisy areas.
• Electronic Ballast: produces high frequency AC and lowers power consumption
for silent operation and ease of dimming.
Advantages of flourescents
- High efficacy (About 80 lm/W)
- Low initial cost
- Long life (about 10,000 - 20,000 hours)
- Variety of color temperatures (improving…no longer just “cool white”) • Dimmable
- For fluorescent lamps, dimming down to 40% of output is possible without substantially reducing luminous efficacy.
Disadvantages of flourescents
• More expensive than incandescent bulbs
High Intensity Discharge (HID):
• A lamp within a lamp that runs at a very high voltage
• An electrical arc is struck across tungsten electrodes in a glass tube filled with
gas and metals
• Metals produce the light once they are heated to a point of evaporation
Advantages of HID Lights
• High efficacy (About 80 lm/W)
Disadvantages of HID Lights
• Produce light that is not flattering to human skin, so not used for commercial/ retail/residential applications
Types of HID Lights
Mercury Vapor:
• Electric arc is passed through high pressure mercury vapor that produces ultraviolet and visibly light
• Primarily in the “blue/green” color
• Moderately high efficacy (30-50 lm/W)
• Have a life of 24,000 hours
• Used for large area overhead lighting in
factories/warehouses/sports complexes/ streetlights
Metal Halide
- Similar to mercury vapor except halides of metal are added to the arc tube
- Increased efficacy (50 - 100 lm/W)
- Have a life of 10,000 hours
- Produces a whiter, more natural light
- Decreased lamp life
High Pressure Sodium
- Produces light by passing an electric arc through hot sodium vapor
- Arc tube must be ceramic to resist hot sodium
- High efficacy (80 - 140 lm/W)
- Have a life of 24,000 hours
- Wide variety of color rendition
Low Pressure Sodium
• Operates like a fluorescent lamp and requires a ballast
• Highest efficacy (150 lm/W)
• Require a brief warmup period to reach
full brightness
• Produces a monochromatic yellow light
• Used where color rendition is not
important (e.g.: parking garages, street lights)
Light Emitting Diode (LED)
• Solid State Lighting
• Bulbs without a filament, plasma, or gas
• Low in power consumption with a long
life span
• Diodes emit light when connected in a
circuit
• Run on DC power
• Used for flashlights, signage,
sustainable lighting, phones, video production
Energy Policy Act (EPACT):
set minimum standards for energy efficiency on incandescent and fluorescent lighting.
It eliminated:
- Medium based PAR and R laps of 40W or higher • F40T12
- U-Shaped fluorescents
- Full wattage fluorescents
- All were replaced with ER lams, tungsten-halogen, and T8
Indirect
• 90% - 100% of light output is directed to the ceiling and upper walls of a room
• Almost all of the light reaches the horizontal plane indirectly, it has to bounce off something else first (so the ceiling/walls are basically the light source)
• Suspend 12”-18” from the ceiling minimum
• Allows for uniform lighting, lacks shadows, low
brightness, and is highly diffuse
• Pretty inefficient system
• Good for offices, lounges, waiting areas
Semi Indirect
- 60% - 90% of light is directed upward, similar to indirect lighting, but more efficient
- 10% - 40% of light is directed downward
- Direct and reflective glare is relatively low
- Kind of a monotonous system
• Good for offices, lounges, waiting rooms, corridors,
Diffuse/ Direct- Indirect
• Equal distribution of light up and downwards • Bright ceilings and upper walls
• All surfaces are lit
• Give light in all directions, and should be
suspended 12” min from the ceiling • Efficient system
• Good for classrooms, standard office works spaces, merchandising areas
Semi Direct
- 60% - 90% of light is directed downward • 10% - 40% of light is directed upward
- Shadowing should not be a problem
- A pleasant environment
- Inherently efficient
• Offices, classrooms, shops, working areas
Direct
• Essentially all light is directed downward
• Ceiling illumination comes from floor and
furnishing reflection
• Requires a light, high reflectance, diffuse floor
unless a dark ceiling is desired
• Efficiency depends on if the distraction is spread
or concentrating
• Gives little surface illumination, requiring the
addition of perimeter lighting
• Downlights create a sharp, theatrical atmosphere,
not good for working spaces
• Can be gloomy and cavelike
- General lighting if spread-type
- Highlights, local, supplemental lighting, and privacy atmosphere lighting if concentrated-type
Retractable:
moveable devices that can adjust the total transmission of light (eg: shutters, roller blinds, and louvers)
Fixed Redistribution Devices:
fixed devices that obscures part of the sky through which the sun passes (eg: overhangs, lightshelves)
Fixed reduced transmission Devices:
glazed openings are made to have permanently reduced transmission (eg: fixed grids, perforated sheets, tinted/reflective/ fritted glass)
Selective High Performance Glazing:
glass that has a lower transmission for the invisible part of the spectrum than the visible, best used with Retractable or Fixed Redistribution Devices
Light Trespass:
unwanted light on private property (e.g.: spill light from a streetlight
enters a bedroom window)
Group Replacement:
the replacement of a group of lights based on their
calculated lifetime use estimates
Spot Replacement:
the replacement of light that have actually burned out
Baffles
• A shield of metal, wood or plastic used to screen a light source from normal angles of
viewing.
• Aluminum baffles are commonly used in parabolic fixtures or, a grooved cylinder
dropped below a light source to conceal the lamp and provide light cutoff.
Diffuser
A device through which the light from a fixture enters a room
Ballast
A device used in fluorescent and HID luminaries. Job is:
• To supply controlled voltage to heat the lamp filaments in preheat and rapid start
circuits
• To supply sufficient voltage to start the lamp by striking an arc through a tube
• To limit the lamp current once the lamp is started
• Ballast (Cold Weather): designed to provide sufficient starting voltage for fluorescent lamps in cold weather, generally down to 0 ̊ F.
• Ballast (Dimming): Dimming ballasts are special ballasts which, when used together with a dimmer control, will vary the light output of a lamp.
Emergency/Exit Lighting:
Install LED (light emitting diode) lighting for exit signs. LED lighting lasts longer than incandescent and is far less expensive to operate.
Variables that must be considered when designing for daylighting include …
glass transmittance
height of the head of the glass
surface reflection inside room and nearby outside surfaces
obstruction (overhangs, trees)
brightness of the sky
area of glass
Longitude of the site is not a factor in daylighting design. Latitude of the site might have a minor influence on how a daylighting design is implemented but is not ciritical.
For a window with no light shelf, daylighting is effective for a distance of ….
1.5 times the head height of the window.
With a light shelf, the effective distanceincreases to about 2.0 to 2.5 times the head height.
What is the equation for inverse square law?
E=Id^2
E = Illuminance
I = Instensity
d = distance
How do you find luminance when given footcandles (fc) and reflectance
Luminnace = fc(reflectance)
What units would be used to measure the brightness of daylight coming through a window?
footlambert
Footlambert is the unit of measure of the brightness (or luminance of a surface and takes into account the transmittance of properties of the glass.
Advantages of parabolic louvers
- good in avaoiding veiling reflections
- effective in avoiding direct glare
Disadvantages of parabolic louvers
- Vertical sourfaces are not well illuminated
- veiling reflections on horiztonal surfaces
If a surface is perpendicular to the direction of the source, the illumination is determined by the formula
E = Id^2
E= illumination (fc)
I=luminous intensity (candlepower)
d=distance
If a surface is NOT perpendicular to the direction of the source, the illumination is determined by the formula
E=I(cosine of theta)/d^2
E=Illumination (fc)
I=luminous intensity
d=distance
Illuminance levels and illuminance categories are used to:
establish quantative lighting system design criteria
Which of the following light sources has the highest luminous efficacy?
metal halide
standard incandescent
tungsten halogen
flourescent
metal halide
At a solar altitude of 30 degrees, one can expect a daylight illuminance of about 10,000 lux with no direct sun and ____ with direct sun.
40,000 lux
Operating a 120-V lamp at 125 V would result in lowered:
hours of life
The ____ lamp is most widely used in accent and display lighting applications.
MR 16
mulitfaceted reflector, halogen
ANSI/ASHRAE/IESNA Standard 90.1 sets forth design requirements for efficient use of energy for the following environmental systems of a building:
lighting, HVAC, electrical, power, water, and energy management
Which calculation method can be used to calculate daylight at any location in a room?
Daylight Factor
When artificial light is provided, what is the minimum lighting level permitted for the entire room, measured how high from finish floor?
10 fc minimum measured at 30 in AFF
What are recoverable light loss factors?
Facotrs that can be reduced by preventative maintenance:
lamp lumen depreciation
lamp burnouts
fixture dirt depreciation
room surface dirt depreciation
What are non-recoverable light loss factors?
Factors that cannot be reduced by preventative maintenance: ambiant fixture temperature
supply voltage depreciation
ballast factos
optical factor
fixture surface depreciation
What is the main reason why ceilings and upper walls are painted white?
TO make glare from ceiling lights less noticeable
What mandates minimum efficacy in lumens per watt and minimum color rendering index for flourescent lamp types?
The national Energy Policy Act of 1992 (EPact)
Flourescent lamps with efficacies of about 85 lm/W are one of the most efficient light sources available. They convert about ___ percent of their energy to useful light.
25
