BUILDING SERVICES - LIGHTING.pdf

COMPILED BY: Syedali Fathima, Asst.Professor
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BUILDING SERVICES –II (Electrical and Mechanical)

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Five characteristics of light are:
Light consists of packets of energy called photons.
Light is the relatively narrow frequency band of
electromagnetic waves.
Light travels at such a high speed, 3 × 10 8 m/sec.
Light behaves both as a wave and particle.
Light travels fast in a vacuum.
• Light or visible light is electromagnetic radiation within the portion of the electromagnetic
spectrum that is perceived by the human eye.
• Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm),
between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths).
• This wavelength means a frequency range of roughly 430–750 terahertz (THz).
• The primary properties of visible light are intensity, propagation-direction, frequency or
wavelength spectrum and polarization.
Light is an electromagnetic wave. Light is a transverse
wave, and does not need any medium to travel. ... Light can
travel through vacuum.

SRM SCHOOL OF ENVIRONMENT ARCHITECTURE AND DESIGN – TN 26
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What are the Properties of Light?
• Light travels in a straight line.
• The speed of light is faster than sound. Light travels at a speed of 3 x 108 m/s.
Following are the important properties of light –
a) Reflection of light.
b) Refraction of light.
c) Diffraction of light.
d) Interference of light.
e) Polarization of light.
f) Dispersion of light.
g) Scattering of light.

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 Reflection of light
Reflection is the phenomenon in which light travelling in one medium, incident on the surface of
another returns to the first medium, obeying the laws of reflection. According to the laws of
reflection
• The incident ray, the reflected ray and the normal to the surface at the point of incidence all lie
in the same plane.
• The angle of incidence is equal to the angle of reflection.

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 Refraction of light
Refraction is a phenomenon in which there is a change in the speed of light as it travels from one
medium to another and there is a bending of the ray of light. The refracted ray obeys the following
laws.
• The incident ray, the refracted ray and the normal to the surface at the point of incidence all lie in
the same plane.

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Diffraction of light
The phenomenon of bending of light around corners of small obstacles and hence it’s
encroachment into the region of the geometrical shadow is called diffraction.
Interference of light
Interference is the phenomenon of modification in the intensity of light due to redistribution of
light energy in the region of superposition of two or more light waves.

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Polarisation of light
Normal light vibrates in all directions
perpendicular to the propagation of light. If the
light is constrained to vibrate in only one
particular plane, then the light is called
polarised light. The phenomenon is called
polarisation.
Dispersion of light
The splitting of a ray of white light into its
constituent colours is called dispersion.
Scattering of light
When sunlight enters the atmosphere of the
earth, the atoms and molecules of different
gasses present in the air absorb the light. Then
these atoms re-emit light in all directions. This
process is known as Scattering of light.

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LUMINOUS FLUX
Luminous flux, or luminous power, is the measure of the perceived power of light. It differs from the
measure of the total power of light emitted, termed 'radiant flux', in that the former takes into
account the varying sensitivity of the human eye to different wavelengths of light.
Luminous flux: it is defined as the total quantity of light energy emitted per second from a
luminous body. It is represented by symbol F and is measured in lumens. The concept of luminous
flux helps us to specify the output and efficiency of a given light source.
Lumen: The lumen is the unit of luminous flux and is defined as the amount of luminous flux
given out in a space represented by one unit of solid angle by a source having an intensity of one
candle power in all directions.
Lumens = candle power X solid angle = cp X w.

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The candela is the base unit of luminous intensity
in the International System of Units (SI); that is,
luminous power per unit solid angle emitted by a
point light source in a particular direction.
Candle: It is the unit of luminous intensity. It is
defined as 1/60th of the luminous intensity per
cm2 of a black body radiator at the temperature of
solidification of platinum (2,0430K).
Luminous intensity: Luminous intensity in any
given direction is the luminous flux emitted by the
source per unit solid angle, measured in the
direction in which the intensity is required. It is
denoted by symbol I and is measured in
candela(cd) or lumens/steradian.

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RECOMMENDED LUX IN SCHOOLS
Foot Candle: It is the unit of illumination which is equal to that given by a source of candela at a distance of
one foot (Equivalent to one lumen per sqft)

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Plane angle:
A plane angle is the angle subtended at a
point in a plane by two converging lines. It is
denoted by the Greek letter ‘Q’ (theta) and is
usually measured in degrees or radians.
Solid angle: Solid angle is the angle subtended
at a point in space by an area, i.e., the angle
enclosed in the volume formed by numerous
lines lying on the surface and meeting at the
point. It is usually denoted by symbol ‘.’ and is
measured in steradian.

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ILLUMINATION: When the light falls upon any surface, the phenomenon is called the illumination.
It is defined as the number of lumens, falling on the surface, per unit area.
It is denoted by symbol E and is measured in lumens per square meter or meter-candle
or lux.
If a flux of F lumens falls on a surface of area A, then the illumination of that surface is E =F/A
lumens/m2 or lux.
Lux or meter candle: It is the unit of illumination and is defined as the luminous flux
falling per square meter on the surface which is everywhere perpendicular to the rays
of light from a source of one candle power and one meter away from it.
Utilization factor or co-efficient of utilization:- It is defined as the ratio of total lumens reaching
the working plane to total lumens given out by the lamp.

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LIGHTING SCHEMES
• Lighting schemes are classified according to the location, requirement and purpose etc. are as
under :
1. Direct lighting
2. Indirect lighting
3. Semi direct lighting
4. Semi indirect lighting
5. General lighting
Direct Lighting
• 90 to 95 % light falls directly on the object or the surface.
• The light is made to fall upon the surface with the help of deep
reflectors.
• Such type of lighting scheme is most used in industries and commercial
lighting.
• It is most efficient but it is liable to cause glare and shadows.
Indirect Lighting
• In this system, the light does not fall directly on the surface but more
than 90 % of light is directed upwards by using diffusing reflectors.
• The ceiling acts as a source of light and this light is uniformly distributed
over the surface and glare is reduced to minimum.
• It provides shadow less illumination which is useful for drawing offices.
• It is also used for decoration purposes in cinema halls, hotels etc.

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Semi direct Lighting
• This is also an efficient system of lighting and chances of glare are also reduced.
• Here transparent type shades are used through which about 60 % light is directed downward
and 40 % is directed upward.
• This also provides a uniform distribution of light and is best suited for room with high ceilings.
Semi indirect Lighting
• In this system about 60 to 90 % of total light is thrown upward to the ceiling for diffused
reflection and the rest reaches the working plane directly.
• A very small amount of light is absorbed by the bowl.
• It is mainly used for interior decoration.
Diffused lighting
• Diffused light, or soft light, is light that's filtered by something. Sunlight through a sheer
curtain is diffused. Light from behind a lampshade is diffused compared to the direct light of a
bare bulb. The lampshade softens and scatters the light

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Ambient lighting
Ambient lighting is also called general lighting, and it's the most basic of the three types of
lighting. It's the natural light from your windows, and the lighting that substitutes for natural light.
Among the fixtures that provide ambient lighting are:
• Chandeliers and other ceiling fixtures
• Light kits on ceiling fans
• Track lighting
• Recessed ceiling lights

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Task lighting
Task lighting is the light you need to perform tasks―reading, studying, cooking, applying makeup,
etc.
Task lighting fixtures include:
• Table lamps
• Desk lamps
• Swing arm lamps
• Under counter lights
• Pendant lights
• Directed track or recessed lights
• Vanity lights
• Adjustable floor lamps

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Accent Lighting:
In addition to providing atmosphere and influencing mood, accent lighting is used to
highlight architectural features and important objects, and to draw attention away from the
things that aren't as pleasing.
Some examples of accent lighting are:
• Can lights and uplights
• Picture lights
• Candlelight
• Directed track or recessed lights
• Niche lighting
• Chandeliers with dimmer switches
• Lighting inside glass or wire door cabinets

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A) Luminous flux: it is defined as the total quantity
of light energy emitted per second from a luminous
body.
The lumen is the unit of luminous flux, a measure of
the total quantity of visible light emitted by a
source per unit of time .
Lumens measure how much light you are getting
from a bulb.
B) Luminous intensity: Luminous intensity is the
luminous flux emitted by the source per unit solid
angle, measured in the direction in which the
intensity is required.
Candle power ( CP) is a unit of measurement
for luminous intensity. It expresses levels of light
intensity relative to the light emitted by a candle of
specific size.
C) ILLUMINATION: When the light falls upon any
surface, the phenomenon is called the illumination.
Lux is used to measure the amount of light output
in a given area - one lux is equal to one lumen per
square meter

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Candle power ( CP) is a unit of measurement for luminous intensity. It expresses levels of light intensity relative to the light
emitted by a candle of specific size.

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PROBLEM-01 :
A fluorescent tube of 20W. Find the luminuous flux of it:
Luminous Flux : The total quantity of light energy emitted per second
Power Rating of fluorescent Tube – 20W
Luminous Efficiency of fluorescent tube -- ???
Luminous Efficiency of fluorescent tube – 50 -60 Lumens/Watt
Luminous Flux = Luminous Efficiency x Power rating
=(50 x20) to (60x20) lumens = 1000 to 1200
Luminous
efficiency is a
measure of
how well a
light source
produces
visible light.

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PROBLEM -02:
• An office area has length: 20 meter; width: 10 meter; height: 3 meter.
• The ceiling to desk height is 2 meters.
• The area is to be illuminated to a general level of 250 lux using twin lamp 32 watt CFL luminaires
with a SHR of 1.25.
• Each lamp has an initial output (Efficiency) of 85 lumen per watt.
• The lamps Maintenance factor (MF) is 0.63 ,Utilization Factor is 0.69 and space height ratio (SHR)
is 1.25.
1. Total wattage of fixtures:
Total wattage of fixtures = No. of lamps x each lamp’s Watt
Total Wattage of fixtures = 2 x 32 = 64 Watts
2. Lumens per fixtures:
Lumens per fixtures =Lumen Efficiency (Lumen per Watt)
x each fixture’s watt
= 85 X 64 = 5440 Lumens
(The wattage and the lumens, are the two values you need to determine a light bulb's efficiency.
And they should be marked on the packaging. Once you've found those two numbers, simply divide
the number of lumens by the number of watts.)
Twin lamp 32 watt CFL luminaires
UTILIZATION FACTOR - The utilization factor or
use factor is the ratio of the time that a piece of
equipment is in use to the total time that it
could be in use. The lighting manufacturers'
catalogues give Utilization Factors for standard
conditions.
MAINTAINENCE FACTOR
A lighting system's maintenance factor indicates
how much of the initial luminous flux remains
available at the end of its service life

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3. Number of fixtures:
Required Number of fixtures =Required Lux x Room Area /MF x UF x Lumen per fixture
Required Number of fixtures = (250 x 20 x 10)/ 0.63 x 0.69 x 5440
= 21 fixtures
4. Minimum Spacing between each fixture:
The ceiling to desk height is 2 meters and space height ratio (SHR) is 1.25.
Minimum Spacing between each fixture: 2 x 1.25 =2.25m
Spacing Height Ratio is defined as the ratio of the distance between adjacent luminaires
(centre to centre), to their height above the working plane.

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5. Number of required rows of fixtures along with width of room
Number of rows required = Width of room /Max. spacing
= 10/2.25
= 4
6. Number of fixtures required in each row
Number of fixtures required in each row = Total fixtures /Number of rows
= 21/4
= 5

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7. Axial spacing between each fixture
Axial spacing between each fixture = Length of room /No. of fixtures in a row
= 20/5
= 4m
8 . Transverse spacing between each fixture
Transverse spacing between each fixture = Width of room /No. of row
= 10/4
=2.5m

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PROBLEM -03:
• An office area has length: 20 meter; width: 11.3meter; height: 3 meter.
• The area is to be illuminated to a general level of 200 lux using twin lamp 32 watt CFL luminaires
with a SHR of 1.25.
• Lumens per fixture =4000
• The lamps Maintenance factor (MF) is 0.80 ,Utilization Factor is 0.60.
Required Number of fixtures =Required Lux x Room Area /MF x UF x Lumen per fixture
= 200 x 20 x 11.3/ 0.60 x 0.80 x 4000
= 5260 / 1920
= 3 Lamps

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TYPES OF LAMPS
a) Incandescent Lamp (Filament Lamp)
1. It should have high melting point (3500º C).
2. It should have high resistivity.
3. It should have low temperature co-efficient.
4. It should have low vapor pressure.
5. Mechanically Strong, ductile.
6. Material used for filament is Carbon, Osmium
tantalum and Tungsten.
7. Gas used inside the lamp ( Nitrogen or Argon )
8. Life: 1000 Hrs working hrs.
9. Lamp efficiency: 10 - 20 lumens/watt
Working:
• Lamp work on the principal of Incandescence( i.e. when a hot body is heated, radiant energy is emitted in
waveform).
• An incandescent bulb generates light through heat.(95% Heat,5% Light)
• When electrical current passes through the tungsten filament, it heats to the point where it glows and gives
off a yellow-red light.
• To keep the filament from burning up immediately, it's housed in a vacuum. Even so, the intense heat of the
filament ensures a comparatively short and expensive life span.
• Applications: Domestic, Commercial and Industrial. Etc…

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2. Fluorescent Tube:
• A fluorescent lamp tube is filled with a gas containing low pressure mercury vapor and argon, xenon,
neon, or krypton.
• The pressure inside the lamp is around 0.3% of atmospheric pressure.
• The inner surface of the lamp is coated with a fluorescent (and often slightly phosphorescent)
coating made of varying blends of metallic and rare-earth phosphor salts.
• The lamp's electrodes are typically made of coiled tungsten and usually referred to as cathodes
because of their prime function of emitting electrons. For this, they are coated with a mixture of
barium, strontium and calcium oxides chosen to have a low thermionic emission temperature.

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Working:
Cathode filament emitting electrons after getting heated due to supply of current . These electrons while
accelerating collide with Argon and Mercury vapour atoms. The excited atoms of Mercury give a radiation.
Applications:
1.In residences, fluorescent lamps are mostly found in kitchens, basements, and garages.
2. In countries, like India…
i) Residential.
ii) Commercial.
iii) Small scale industries ….Etc.

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3. Halogen Lamps.
Wattage:
20/50 w 12 V
300w, 500w, 1000w 230 V.
Efficiency- 15 to 25 lumen/watt
500 W Tungsten Halogen Lamp

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Applications:
1. Indoor lighting.
2. Outdoor lighting.
3. Flood lighting.
4. For vehicle head lights.
5. TV studios
6. Photo film.
7. Signaling.
8.Large gardens.
9.Fountains.
10. Airport runways.

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4.Compact Fluorescent Lamp (CFL)
CFL
1) Life Span: 6000-15,000 Hrs
2) Energy consumption: Less
3) Cost :More
4) Starting time: Take time to give
full illumination

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5.High Pressure Mercury Vapour Lamp.
• This lamp start with a small arc
between the starting electrode and the
main electrode.
• This arc goes through argon gas which
easily strikes, even in cold weather.
• This little arc heats the tube, and over
Several minutes the tube gets hot
enough to vaporize the solid mercury
stuck to the sides.
• The mercury vaporized creates a strong
light between the two main electrodes.
• The mercury vapor lamp is a negative resistance device.
• This means its resistance decreases as the current through the tube increases.
• So if the lamp is connected directly to a constant-voltage source like the power lines, the current through it
will increase until it destroys itself.
• Therefore it requires a ballast to limit the current through it.

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6. LED ( Light Emitting Diode) Lamps:
LEDs are semiconductor devices that produces
Light when an electrical current applied to them.
Latest Lighting Technology.
Invented in 1962.
Lower energy consumption.
Longer life : 50,000 – 100,000 Hrs.
Smaller size , Faster switching.
Dimming.
Efficiency: 30-60 lumens/watt or 100 -130 lumens/watt
RGB-Method mixing the proper
amount of light from red, green, blue.
LED yield white light.
Application:
1) Signs and Traffic signals.
2) Displays.
3) Exit signs.
4) Indicators and Flash lights.
5) Under counters. Etc.

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WHAT IS DIODE?
A semiconductor device with two terminals which allows the flow of current in one direction.
WHAT IS A LED?
A light-emitting diode (LED) is a two-lead semiconductor light source. It is a pn junction diode, which emits light
when activated.
When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes within the
device, releasing energy in the form of photons.
Light Emitting Diode
A light-emitting diode (LED) is a semiconductor device that emits visible light when an electric current passes
through it. The light is not particularly bright, but in most LEDs it is monochromatic, occurring at a single
Wavelength.
LEDs convert electrical energy into light energy. They are frequently used as "pilot" lights in electronic appliances
to indicate whether the circuit is closed or not.

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About LEDs
The most important part of a light emitting diode (LED) is the semi conductor chip located in the center of the
bulb as shown at the right. The chip has two regions separated by a junction. The p region is dominated by
positive electric charges, and the n region is dominated by negative electric charges. The junction acts as a
barrier to the flow of electrons between the p and the n regions.
Only when sufficient voltage is applied to the semi-conductor chip, can the current flow, and the electrons cross
the junction into the p region.

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ILLUMINATION
•Architectural Lighting
•Signage (Channel Letters)
•Machine Vision
•Retail Displays
•Emergency Lighting (Exit Signs)
•Neon Replacement
•Bulb Replacements
•Flashlights
•Outdoor Accent Lighting - Pathway,
Marker Lights

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ADVANTAGES
Efficiency: LEDs emit more lumens per watt than incandescent light bulbs. The efficiency of LED lighting fixtures is
not affected by shape and size, unlike fluorescent light bulbs or tubes.
Color: LEDs can emit light of an intended color without using any color filters as traditional lighting methods
need. This is more efficient and can lower initial costs.
Size: LEDs can be very small (smaller than 2 mm2)and are easily attached to printed circuit boards.
Warmup time: LEDs light up very quickly. A typical red indicator LED will achieve full brightness in under a
microsecond. LEDs used in communications devices can have even faster response times.
Cycling: LEDs are ideal for uses subject to frequent on-off cycling, unlike incandescent and fluorescent lamps that
fail faster when cycled often, or high-intensity discharge lamps (HID lamps) that require a long time before
restarting.
Dimming: LEDs can very easily be dimmed either by pulse-width modulation or lowering the forward current.
This pulse-width modulation is why LED lights, particularly headlights on cars, when viewed on camera or by some
people, appear to be flashing or flickering. This is a type of stroboscopic effect.
Slow failure: LEDs mostly fail by dimming over time, rather than the abrupt failure of incandescent bulbs.

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Lifetime: LEDs can have a relatively long useful life. One report estimates 35,000 to 50,000 hours of useful life,
though time to complete failure may be longer. Fluorescent tubes typically are rated at about 10,000 to 15,000
hours, depending partly on the conditions of use, and incandescent light bulbs at 1,000 to 2,000 hours.
Several DOE demonstrations have shown that reduced maintenance costs from this extended lifetime, rather
than energy savings, is the primary factor in determining the payback period for an LED product.
Shock resistance: LEDs, being solid-state components, are difficult to damage with external shock, unlike
fluorescent and incandescent bulbs, which are fragile.
Focus: The solid package of the LED can be designed to focus its light. Incandescent and fluorescent sources
often require an external reflector to collect light and direct it in a usable manner. For larger LED packages total
internal reflection (TIR) lenses are often used to the same effect. However, when large quantities of light are
needed many light sources are usually deployed, which are difficult to focus or collimate towards the same
target.
DISADVANTAGES
High initial price : LEDs are currently more expensive, price per lumen. In 2012, the cost per thousand lumens
was about $6.
Light Quality: Most cool-white LEDs have spectra that differ significant from a black body radiator like the sun
or an incident light.
Temperature dependence: Driving the LED hard in high ambient temperatures may result to overheating of the
led package ,eventually leading to device failure.
Voltage sensitivity: LEDs must be supplied with a voltage above their threshold voltage and a current below
their rating. Current and lifetime change greatly with a small change in applied voltage. They thus require a
current-regulated supply (usually just a series resistor for indicator LEDs).

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CONCEPT OF SUSTAINABILTY IN ILLUMINATION
• Artificial lighting can account for up to 15% of a building’s annual
electricity use. Use of current lighting technology and designing
to minimize the need for artificial lighting can decrease lighting
energy use in buildings by 50-70%.
• Occupancy sensors that automatically turn lights on and off as
needed can reduce energy use while having a minimal impact on
building occupants. Opportunities for daylighting should be
maximized, while controlling glare and unwanted heat gain.
Orientation
• South facing windows with appropriate overhangs provide
indirect light in the summer, and both heat and light during the
winter.
• East and west facing windows let in light during the morning and
evening, but may cause glare and admit heat during the summer.
• North facing windows can also be used for daylighting, as they
admit relatively even, glare-free light and almost no unwanted
summer heat gain.
• The number, size and glass type of north facing windows should
be carefully considered, however, as they do not contribute to
passive solar heat gain in the winter, and lose more heat than
insulated walls.

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Reflected Light
• Reflecting light reduces glare and allows it to reach areas that would otherwise lack natural light.
• Painting interior walls and ceilings a light color can help provide reflected light.
• Light shelves are a good strategy for providing shade for south facing windows and reflecting light deep in
to a space.
• A light shelf is a horizontal light reflecting overhang placed above eye level with a transom window placed
above it. External shelves are more effective at providing shading than interior shelves, but a combination
of the two will work best to provide even lighting.

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Clerestory Windows:
• Clerestory windows are vertical windows near the top of a wall.
They bring light in high up in a room and illuminate the ceiling.
The reflected light from the ceiling is a soft, indirect light and
mimics skylighting. They also allow light to penetrate deeper in to
room than windows set at a standard height, especially when
used in combination with adjacent light colored overhangs and
light colored ceilings.
Lighting Controls:
• While most people recognize that turning off lights saves energy, it’s easy to forget or fail to notice
that lights are on and not being used. Lighting controls can reduce energy use by automatically
turning lights on and off as needed.
• Photosensors and motion detectors are most commonly used with outdoor lighting. Photosensors
can be used to prevent outdoor lights from operating during the day, while motion detectors can
turn lights only when they are needed.
• Occupancy sensors are generally used indoors to turn lights on when a person enters a room and
turn them back off when no activity is detected for a period of time. Occupancy sensors need to be
located where they will detect occupants or activity in all parts of the room.

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WHAT IS ENERGY AUDIT:
• An energy audit is an official scientific study of energy consumption of an
organisation/process/plant/equipment aimed at reduction of energy consumption and energy
costs without affecting productivity and comforts and suggesting the methods for energy
saving and reduction in energy cost.
NEED FOR ENERGY AUDIT
• In any industry, the three top operating expenses are often found to be energy (both electrical
and thermal), labour and materials. If one were to relate to the manageability of the cost or
potential cost savings in each of the above components, energy would invariably emerge as a
top ranker, and thus energy management function constitutes a strategic area for cost
reduction.
• Energy Audit will help to understand more about the ways energy and fuel are used in any
industry, and help in identifying the areas where waste can occur and where scope for
improvement exists.
• The Energy Audit would give a positive orientation to the energy cost reduction, preventive
maintenance and quality control programmes which are vital for production and utility
activities. Such an audit programme will help to keep focus on variations which occur in the
energy costs, availability and reliability of supply of energy, decide on appropriate energy mix,
identify energy conservation technologies, retrofit for energy conservation equipment etc.

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TYPE OF ENERGY AUDIT
The type of Energy Audit to be performed depends on:
- Function and type of industry
- Depth to which final audit is needed, and
- Potential and magnitude of cost reduction desired.
Thus Energy Audit can be classified into the following two types.
- Preliminary Audit
- Detailed Audit
Preliminary Energy Audit Methodology
Preliminary energy audit is a relatively quick exercise to:
- Establish energy consumption in the organization
- Estimate the scope for saving
- Identify the most likely and the easiest areas for attention
- Identify immediate (especially no-/low-cost) improvements/ savings
- Set a ‘reference point’
- Identify areas for more detailed study/measurement
- Preliminary energy audit uses existing, or easily obtained data

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Detailed Energy Audit Methodology
• A comprehensive audit provides a detailed energy project implementation plan for a facility,
since it evaluates all major energy using systems.
• This type of audit offers the most accurate estimate of energy savings and cost. It considers
the interactive effects of all projects, accounts for the energy use of all major equipment,
and includes detailed energy cost saving calculations and project cost.
• In a comprehensive audit, one of the key elements is the energy balance. This is based on an
inventory of energy using systems, assumptions of current operating conditions and
calculations of energy use.
• This estimated use is then compared to utility bill charges. Detailed energy auditing is
carried out in three phases: Phase I, II and III.
- Phase I - Pre Audit Phase
- Phase II - Audit Phase
- Phase III - Post Audit Phase

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What Is a Lighting Audit?
• A Lighting Audit is an onsite
walkthrough of an existing facility to
document the current lighting
conditions and determine where
energy saving changes can be made.
• It can be conducted for both exterior
and interior spaces, and involves
collecting four main types of
information: general, lighting,
occupant, and financial.
GENERAL INFORMATION
• General information includes floor
plans and ceiling plans that show
current fixture locations. Room
dimensions, as well as ceiling heights
are also documented.
• Any future plans for renovation are
also collected, if available.

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LIGHTING INFORMATION
• Lighting information for each area being considered is also collected. This includes information
such as the:
1. Number of fixtures
2. Type and size of fixtures
3. Number of lamps per fixture or ballast
4. Type of lamps or ballasts
5. Fixture wattage
6. Tasks performed in the space
7. Hours of operation in the space
8. Height at which tasks are performed
9. Availability of natural daylight
OCCUPANT INFORMATION
• It is also important to know how occupants feel about their current lighting system, as their
insight can provide information to fill the gaps a physical inspection cannot determine.
• This step usually involves interviews or surveys, where the auditor asks the regular occupants of
each space to reflect on how the lighting currently affects them.
• Questions can include whether occupants are experiencing glare on their computer screen, if
they find the lighting too dim when they work at their stations or whether it is too bright
(especially in areas where there is natural light) during the day.

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FINANCIAL INFORMATION
• With the physical space and how users react to it documented, the last step of a Lighting
Audit is to collect financial information.
• Knowing the average charges for electricity (kWh) and demand (kW) is important to
calculating current operating costs and the eventual long-term savings gained from
replacing everything with energy-saving fixtures.
HOW TO CONDUCT A LIGHTING AUDIT: OUR 6-STEP CHECKLIST
STEP 1
Identify each space. Is it an office? Warehouse? Retail showroom? Parking lot? Note any
special conditions such as windows or skylights.
STEP 2
Specify each existing fixture type, noting each one’s:
- Wattage
- The number of hours used per week
- Additional notes such as any existing controls/sensors, mounting height or special usage
conditions

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STEP 3
Calculate the approximate Annual Burn Hours (the number of hours fixtures in a space are
turned on per year).
STEP 4
Determine the fixtures’ Kilowatt (kW) rate (how many Kilowatts the fixtures use).

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STEP 5
Find the average Kilowatt per Hour (kWh) rate based on the customer’s three most recent utility
bills.
STEP 6
Calculate the existing energy expense of all fixtures.
The end result is the facility’s current lighting cost. Having this number allows you to show how
your recommended energy-efficient replacements will drastically lower their month-to-month
operating expenses.

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LIGHTING AUDIT TIPS
While a Lighting Audit is straightforward, every space can be different. The following is our list of
tips to consider for achieving the most accurate assessment:
Accurate system wattage. Fixtures are often suspended high in the ceiling, but knowing each
one’s wattage is crucial to the overall calculation. Don’t assume system wattage is the same for
every fixture just because they look the same.
Space usage seasonality. A space can be used differently in different times of the year. A
warehouse may be used for packing, storing, and shipping during peak season–but is then re-
configured for storage only when off-peak. Knowing this not only changes the annual burn rate
and energy expense; it can also affect the new fixtures that are proposed.
Room surface reflectances. Bright surfaces in a room reflect light, making things brighter while
dark areas absorb light, requiring more lumen output to sufficiently illuminate a room. Therefore,
it is important to note the current color of floors, walls and ceilings and know if there are any
planned changes.
Opportunity for controls. Understanding how each space is used allows you to suggest the use of
simple controls that detect motion, perform daylight harvesting functions or work on a timer,
providing further savings opportunities.

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Maintenance (or lack of). Replacing current fixtures and lamps with those that are long-life
will result in maintenance savings, particularly in areas with difficult-to-access fixtures. Make
a note of this major selling point.
Space dimensions matter. Having the accurate dimensions of the space (length in feet, width
in feet, ceiling heights in feet and areas in square feet) is important to a successful audit. Be
aware that renovation work could have been performed since the original building was built
so the floor plan you have may not reflect the current fixture layout in the ceilings.
Don’t manipulate hours to get meet ROI targets. We have seen some auditors in the past
bump the hours of operation of fixtures in order to inflate the cost of system operation to
reduce the payback period. Avoid this because the customer will eventually see that their
payback period is longer than your proposal; this could seriously affect your long-term
relationship with them.

BUILDING SERVICES - LIGHTING.pdf

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