1. EH 342 Building construction IV
Sources of light
Lighting or illumination is the deliberate application of light to
achieve some practical or aesthetic effect.
Lighting includes the use of both artificial light sources such as
lamps and light fixtures, as well as natural illumination by capturing
daylight.
Daylighting (using windows, skylights, or light shelves) is often
used as the main source of light during daytime in buildings.
This can save energy compared with artificial lighting, which
represents a major component of energy consumption in
buildings. Without proper design, energy can be wasted by using
too much lighting, or using out-dated technology.
Proper lighting can enhance task performance, improve the
appearance of an area, and have positive psychological effects on
occupants.

2. EH 342 Building construction IV
Sources of light
One of the core tenets of proper lighting is uniform illumination,
which is required in many applications such as projection displays,
LCD backlights, medical lighting, microscopy, solid-state lighting, and
general lighting.
Indoor lighting is usually accomplished using light fixtures, and is a
key part of interior design.
Lighting can also be an intrinsic component of landscape projects.

3. EH 342 Building construction IV
Sources of light
Lighting Fixtures
Lighting fixtures come in a wide variety of styles for various
functions
important functions are as a holder for the light source, to
provide directed light and to avoid visual glare.
 Some are very plain and functional, while some are pieces of art
in themselves. Nearly any material can be used, so long as it can
tolerate the excess heat and is in keeping with safety codes.
An important property of light fixtures is the luminous efficacy or
wall-plug efficiency, meaning the amount of usable light
emanating from the fixture per used energy, usually measured in
lumen per watt..

4. EH 342 Building construction IV
Sources of light
 A fixture using replaceable light sources can also have its efficiency
quoted as the percentage of light passed from the "bulb" to the
surroundings.
The more transparent the lighting fixture is, the higher efficacy.
Shading the light will normally decrease efficacy but increase the
directionality and the visual comfort probability.
Color temperature for white light sources also affects their use for
certain applications.

5. EH 342 Building construction IV
Sources of light
Lighting fixtures come in a wide variety of styles for various
functions.
The most important functions are as a holder for the light source, to
provide directed light and to avoid visual glare.
 Some are very plain and functional, while some are pieces of art in
themselves.
Nearly any material can be used, so long as it can tolerate the
excess heat and is in keeping with safety codes.
An important property of light fixtures is the luminous efficacy or
wall-plug efficiency, meaning the amount of usable light emanating
from the fixture per used energy, usually measured in lumen per watt.

6. EH 342 Building construction IV
Sources of light
Lighting is classified by intended use as general, accent, or task
lighting, depending largely on the distribution of the light
produced by the fixture.
Task lighting is mainly functional and is usually the most
concentrated, for purposes such as reading or inspection of
materials.
 For example, reading poor-quality reproductions may require
task lighting levels up to 1500 lux (150 footcandles), and some
inspection tasks or surgical procedures require even higher levels.
Accent lighting is mainly decorative, intended to highlight
pictures, plants, or other elements of interior design or
landscaping.
General lighting (sometimes referred to as ambient light) fills in
between the two and is intended for general illumination of an
area.

7. EH 342 Building construction IV
Sources of light
Forms of lighting include alcove lighting, which like most other
uplighting is indirect.
This is often done with fluorescent lighting (first available at the
1939 World's Fair) or rope light, or occasionally with neon lighting. It
is a form of backlighting.
Soffit or close to wall lighting can be general or a decorative wall-
wash, sometimes used to bring out texture (like stucco or plaster) on
a wall, though this may also show its defects as well.
 The effect depends heavily on the exact type of lighting source
used.
Recessed lighting (often called "pot lights" in Canada, "can lights" or
'high hats" in the US) is popular, with fixtures mounted into the
ceiling structure so as to appear flush with it.
These downlights can use narrow beam spotlights, or wider-angle
floodlights, both of which are bulbs having their own reflectors.

8. EH 342 Building construction IV
Sources of light
These downlights can use narrow beam spotlights, or wider-angle
floodlights, both of which are bulbs having their own reflectors. There
are also downlights with internal reflectors designed to accept
common 'A' lamps (light bulbs) which are generally less costly than
reflector lamps. Downlights can be incandescent, fluorescent, HID
(high intensity discharge) or LED.
Track lighting, invented by Lightolier, was popular at one point
because it was much easier to install than recessed lighting, and
individual fixtures are decorative and can be easily aimed at a wall.
 It has regained some popularity recently in low-voltage tracks,
which often look nothing like their predecessors because they do not
have the safety issues that line-voltage systems have, and are
therefore less bulky and more ornamental in themselves.


9. EH 342 Building construction IV
Sources of light
A master transformer feeds all of the fixtures on the track or rod
with 12 or 24 volts, instead of each light fixture having its own line-
to-low voltage transformer. There are traditional spots and floods, as
well as other small hanging fixtures. A modified version of this is
cable lighting, where lights are hung from or clipped to bare metal
cables under tension.
A sconce is a wall-mounted fixture, particularly one that shines up
and sometimes down as well. A torchiere is an uplight intended for
ambient lighting. It is typically a floor lamp but may be wall-mounted
like a sconce.
The portable or table lamp is probably the most common fixture,
found in many homes and offices.

The standard lamp and shade that sits on a table is general lighting,
while the desk lamp is considered task lighting. Magnifier lamps are
also task lighting.

10. EH 342 Building construction IV
Sources of light
The illuminated ceiling was once popular in the 1960s and 1970s but
fell out of favor after the 1980s.
This uses diffuser panels hung like a suspended ceiling below
fluorescent lights, and is considered general lighting. Other forms
include neon, which is not usually intended to illuminate anything else,
but to actually be an artwork in itself.
This would probably fall under accent lighting, though in a dark
nightclub it could be considered general lighting.
In a movie theater each step in the aisles is usually marked with a
row of small lights, for convenience and safety when the film has
started, hence the other lights are off.
 Traditionally made up of small low wattage, low voltage lamps in a
track or translucent tube, these are rapidly being replaced with LED
based versions.

11. EH 342 Building construction IV
Roof lights and dormers
A dormer is a structural element of a building that protrudes from
the plane of a sloping roof surface.
 Often conflated with the term "dormer", a dormer window is a
window set into the dormer. Like skylights
dormer windows are a source of light and ventilation for top floors,
but unlike skylights (which are flush with the roof surface) they also
increase the amount of headroom in the room and allow for more
usable space.
Examples:
Gable fronted dormer,Hipped roof dormer, Flat roof dormer

12. EH 342 Building construction IV
Roof lights and dormers

13. EH 342 Building construction IV
Luminance
Luminance is a photometric measure of the luminous intensity per
unit area of light travelling in a given direction.
It describes the amount of light that passes through or is emitted
from a particular area, and falls within a given solid angle.
The SI unit for luminance is candela per square metre
 The CGS unit of luminance is the stilb, which is equal to one candela
per square centimetre or 10 kcd/m2.

14. EH 342 Building construction IV
Luminance
Luminance is often used to characterize emission or reflection from
flat, diffuse surfaces.
The luminance indicates how much luminous power will be detected
by an eye looking at the surface from a particular angle of view.
Luminance is thus an indicator of how bright the surface will appear.
In this case, the solid angle of interest is the solid angle subtended by
the eye's pupil.
 Luminance is used in the video industry to characterize the
brightness of displays.
 A typical computer display emits between 50 and 300 cd/m2. The sun
has luminance of about 1.6×109 cd/m2 at noon.
reference
^ "Luminance". Lighting Design Glossary.
http://www.schorsch.com/kbase/glossary/luminance.html. Retrieved
Apr. 13, 2009

15. EH 342 Building construction IV
Light fixtures
Lighting fixtures come in a wide variety of styles for various
functions.

The most important functions are as a holder for the light source,
 to provide directed light and to avoid visual glare. Some are very
plain and functional, while some are pieces of art in themselves.
Nearly any material can be used, so long as it can tolerate the excess
heat and is in keeping with safety codes.
An important property of light fixtures is the luminous efficacy or
wall-plug efficiency, meaning the amount of usable light emanating
from the fixture per used energy, usually measured in lumen per
watt.
A fixture using replaceable light sources can also have its efficiency
quoted as the percentage of light passed from the "bulb" to the
surroundings.

16. EH 342 Building construction IV
Light fittings
The more transparent the lighting fixture is, the higher efficacy.
Shading the light will normally decrease efficacy but increase the
directionality and the visual comfort probability.
Color temperature for white light sources also affects their use for
certain applications.
for white light sources also affects their use for certain applications.
The color temperature of a white light source is the temperature in
Kelvin of a theoretical black body emitter that most closely matches
the spectral characteristics of the lamp.
 An incandescent bulb has a color temperature around 2800 to 3000
Kelvin; daylight is around 6400 Kelvin.

17. EH 342 Building construction IV
Light fittings
Lower color temperature lamps have relatively more energy in the
yellow and red part of the visible spectrum, while high color
temperatures correspond to lamps with more of a blue-white
appearance.
 For critical inspection or color matching tasks, or for retail
displays of food and clothing, the color temperature of the lamps
will be selected for the best overall lighting effect
Lighting is classified by intended use as general, accent, or task
lighting, depending largely on the distribution of the light produced
by the fixture.
Task lighting is mainly functional and is usually the most
concentrated, for purposes such as reading or inspection of
materials. For example, reading poor-quality reproductions may
require task lighting levels up to 1500 lux (150 footcandles), and
some inspection tasks or surgical procedures require even higher
levels.

18. EH 342 Building construction IV
Light fittings
For example, reading poor-quality reproductions may require task
lighting levels up to 1500 lux (150 footcandles), and some
inspection tasks or surgical procedures require even higher levels.
Accent lighting is mainly decorative, intended to highlight
pictures, plants, or other elements of interior design or landscaping.
General lighting (sometimes referred to as ambient light) fills in
between the two and is intended for general illumination of an area.
Indoors, this would be a basic lamp on a table or floor, or a fixture
on the ceiling.
Outdoors, general lighting for a parking lot may be as low as 10-
20 lux (1-2 footcandles) since pedestrians and motorists already
used to the dark will need little light for crossing the area

19. EH 342 Building construction IV
Light fittings
Methods
Downlighting is most common, with fixtures on or recessed in the
ceiling casting light downward. This tends to be the most used
method, used in both offices and homes.
Although it is easy to design it has dramatic problems with glare and
excess energy consumption due to large number of fittings.
lighting is often used to bounce indirect light off the ceiling and back
down. It is commonly used in lighting applications that require minimal
glare and uniform general illuminance levels.
 Uplighting (indirect) uses a diffuse surface to reflect light in a space
and can minimize disabling glare on computer displays and other dark
glossy surfaces.

20. EH 342 Building construction IV
Light fittings
It gives a more uniform presentation of the light output in operation.
 However indirect lighting is completely reliant upon the reflectance
value of the surface.
While indirect lighting can create a diffused and shadow free light
effect it can be regarded as an uneconomical lighting principle.
Front lighting is also quite common, but tends to make the subject
look flat as its casts almost no visible shadows.
Lighting from the side is the less common, as it tends to produce
glare near eye level.

21. EH 342 Building construction IV
Light fittings
Forms of lighting include alcove lighting, which like most other
uplighting is indirect. This is often done with fluorescent lighting
(first available at the 1939 World's Fair) or rope light, or occasionally
with neon lighting. It is a form of backlighting.
Soffit or close to wall lighting can be general or a decorative wall-
wash, sometimes used to bring out texture (like stucco or plaster) on
a wall, though this may also show its defects as well.
The effect depends heavily on the exact type of lighting source
used.
Recessed lighting (often called "pot lights" in Canada, "can lights"
or 'high hats" in the US) is popular, with fixtures mounted into the
ceiling structure so as to appear flush with it.
These downlights can use narrow beam spotlights, or wider-angle
floodlights, both of which are bulbs having their own reflectors.
 There are also downlights with internal reflectors designed to
accept common 'A' lamps (light bulbs) which are generally less costly
than reflector lamps.

22. EH 342 Building construction IV
Light fittings
There are also downlights with internal reflectors designed to
accept common 'A' lamps (light bulbs) which are generally less costly
than reflector lamps.
Downlights can be incandescent, fluorescent, HID (high intensity
discharge) or LED.
Track lighting, invented by Lightolier, was popular at one point
because it was much easier to install than recessed lighting, and
individual fixtures are decorative and can be easily aimed at a wall.
It has regained some popularity recently in low-voltage tracks,
which often look nothing like their predecessors because they do not
have the safety issues that line-voltage systems have, and are
therefore less bulky and more ornamental in themselves.
 A master transformer feeds all of the fixtures on the track or rod
with 12 or 24 volts, instead of each light fixture having its own line-
to-low voltage transformer.
There are traditional spots and floods, as well as other small
hanging fixtures. A modified version of this is cable lighting, where
lights are hung from or clipped to bare metal cables under tension.

23. EH 342 Building construction IV
Task Lighting
The convention is simply to measure the intensity of illumination on
a work plane
Taken to be a horizontal surface situated 0.85m above floor level
This intensity of illumination is known as illuminance and is
measured in lux
The more detail the work been done the higher the level of
illumination on the working plane


24. EH 342 Building construction IV
Task Lighting
Recommended illuminances in electrically lit rooms vary from 150
lux for storage areas to 3000 lux for work surfaces like picking of
small items like diamond
eg:
Domestic living- 50 lux
Offices labs - 500 lux
Out door - 5000 lux
In order for a room to be well lit other consideration should be
given:
relative brightness of surfaces
Modelling characteristics of illumination
Glare control
Colour rendering
Relative brightness


25. EH 342 Building construction IV
Task Lighting
Relative brightness
Adequate lighting should fall not only on the work plan, but ceiling,
walls
A lighting system that will direct light both horizontally as well as
vertically
Sensible colour on the floor, wall and ceiling
Light coloured surfaces make it easier to achieve good light
The appropriate measure of adequate lighting is scalar illuminance
This is the average illuminance over the whole surface of tiny
sphere at a particular point in space due to light arriving from all
directions
eg: if the scalar illuminance of 150 lux is not less than half the
horizontal illumanance of 300 lux then it can assumed that all
surfaces of the room will appear adequately lit
This measurement takes into account the following:
1. the proportions of the room height, length and width
combined into a single figure called the room index(measured with a
nomogram) a

26. EH 342 Building construction IV
Task Lighting
Relative brightness
Adequate lighting should fall not only on the work plan, but ceiling,
walls
A lighting system that will direct light both horizontally as well as
vertically
Sensible colour on the floor, wall and ceiling
Light coloured room surfaces will aid to achieve good scalar
illumination in most rooms
The appropriate measure of adequate lighting is scalar illuminance
This is the average illuminance over the whole surface of tiny
sphere at a particular point in space due to light arriving from all
directions


27. EH 342 Building construction IV
Task Lighting
Relative brightness
This is the average illuminance over the whole surface of tiny
sphere at a particular point in space due to light arriving from all
directions
eg: if the scalar illuminance of 150 lux is not less than half the
horizontal illumanance of 300 lux then it can assumed that all
surfaces of the room will appear adequately lit
Scalar measurement planar measurement
Horizontal illumination measured in lux equals lumen per m2 of
horinzontal surfaces. Scalar illumination is lumens per m2 of
spherical surfaces

28. EH 342 Building construction IV
Task Lighting
Relative brightness
This measurement takes into account the following:
1. the proportions of the room height, length and width
combined into a single figure called the room index(measured with a
nomogram)
2. the reflectances of the major surfaces of the room, floor, wall
and ceiling
3. the pattern of the downward light spread achieved by the
electric light fitting (BZ)
A low BZ number means that downward light distribution tends to
be concentrated
A high BZ number means that downward light distribution tends to
be dispersed
The higher the BZ no. The more light will tend to fall on the walls

29. EH 342 Building construction IV
Task Lighting
Modelling characteristic of illumination
If there is absolutly uniform distribution of light in all direction the
modelling power of the illumination may be adequate
There should be sufficient contrast btn. highlights and shadows to
give the best results without being harsh
Illumination vector – if the point of highest illumination and the
opposite point of lowest illumination are identified on that tiny
notional sphere then both the direction of the light flow will be
known and the illumination difference btn. The two opposite poles
measured in lux.

30.  An illumination vector has both direction and
magnitute (and magnitude being measured in
lux)
 An illumination vector under a downlighter will
be virtually vertical this is usually unpleasant for
most people.
 Single overhead light fitting in the middle of the
room gives good modelling if it emits light side
ways as well down.
 There should be sufficient contrast btn.
highlights and shadows to give the best results
without being harsh
 Illumination vector – if the point of highest
illumination and the opposite point of lowest
illumination are identified on that tiny notional
sphere then both the direction of the light flow
will be known and the illumination difference btn
the two opposite poles measured in lux.
 Taken together the two characteristics will give
us the illumination vector of the lighting in a
room.
 The result will be that one can calculate a vector
comprising both magnitude and direction.

31. Illumination vector continued
 Room finishes and lighting systems
affect the vector magnitude
 i.e. dark coloured floors reflect
little light upwards, therefore the
notional sphere will have a darker
underside than the brighter upper
sphere. Therefore making lighting
in that room unpleasant.
 However lighter floors reflect light
upwards and therefore the notional
sphere will not have a darker
underside, but rather there will be
sufficient upward light flow to give
a pleasant soft modelling.

32. Vector/Scalar ratio
 This is the ratio between the
magnitude of the illumination
vector and the scalar illumination.
 The ratio can be used to estimate
the working measure of the
modelling effect of lighting.
 A ratio higher than 1.8 is
unpleasant, that lower than 1.2
will be indistinct and excessively
soft.
 An ideal ratio would be about 1.5.

33. Tips
• Rooms need to have a
dominant direction of lighting
rather than completely
diffused light
• A good and comfortable
lighting is that of 15 to 45
degrees to horizontal plane.
Therefore side windows in
conjunction with overhead
lighting give good results.
 Low BZ number and
fraction ratio provide
good modelling rooms
with light coloured
floors.
 A high BZ number
with a low fraction
provides better
modelling with dark
coloured floors.

34. Tips
• Risk of glare is increased
with long rooms.
•Low ceilings in large rooms
•Dark decorations
•The lack of diffusers
•Electric fittings with high BZ
value tend to increase glare.
Glare control
 When a room is
brighter than average
it causes visual
discomfort. This is
known as “Glare”

35. Colour rendering
 Incandescent light fittings give a natural look
whereas florescent lights give objects a unnatural
look.
Task lighting
 When the work environment is close to a window
then the required intensity of illumination on the
work plane is described in terms of daylight factor.
 Daylight factor is the ratio of the luminance of the
horizontal plane inside the building compared to
that outside the building at the same instant.
Amenity lighting

36. Amenity light
 Moderately sized side windows will add much to the amenity of
a room by throwing light on wall surfaces
 If the side windows are too large problem of glare and heat
control are likely
 Roof lights may provide very good task lighting, a pronounced
vertical light direction is found unpleasant Incandescent light
fittings give a natural look whereas florescent lights give
objects a unnatural look.
Task lighting
 When the work environment is close to a window then the
required intensity of illumination on the work plane is
described in terms of daylight factor.
 Daylight factor is the ratio of the luminance of the horizontal
plane inside the building compared to that outside the building
at the same instant.