This document discusses concepts and methods for daylighting buildings. It begins by stating that daylight is a renewable source of light that can save energy and create a comfortable environment when utilized for interior lighting. It then describes various daylighting design methods like the use of skylights, clerestories, light shelves, and building orientation. The document also notes some challenges of daylighting like increased heat gain and potential for glare. It provides guidance on daylighting design for different climates.

1. Daylighting
ARCHITECTURAL ILLUMINATION

2. introduction
“ DAYLIGHT IS A RENEWABLE SOURCE OF LIGHT WHOSE UTILIZATION
FOR LIGHTING OFBUILDING INTERIORS DURING THE PERIOD IT IS
AVAILABLE, COULD LEAD TO ENERGY CONSERVATION AND
PROMOTION OFA FRIENDLY ENVIRONMENT.”
 SOURCES OF DAYLIGHTING:
 The primary source of light for daylighting is the sun.
 The light received by the earth from the sun consists of two parts:
 Direct solar illumination
 Design Methods
 For the purpose of the daylighting design, direct solar illumination
shall not be considered and only skylight shall be taken as a
contributing factor to the illuminance of the building interiors during
the day.

3. advantage
s
 The overall objective of daylighting is to
minimize the amount of artificial light and
reduce electricity costs, but it can also lower
HVAC costs as well.
 the overall energy savings range from 15 to
40 percent.
 Reduced cooling loads by 10-20%
 Improved lighting conditions
 Colour Rendition
 Colour Temperature
 “sparkle”
 Occupant Satisfaction
 Occupant Comfort.
 Connection to Nature
 Reducing the amount of electrical energy
used also reduces the amount of greenhouse
gases released that are associated with the
production of said energy.
 Health: circadian rhythms…

4. drawback
sAlthough daylighting can provide numerous positive
results in regards to worker performance, if a daylighting
program has not been executed properly, it can produce
negative results.
 Increased heat gains.
 A high-performance daylighting system may initially
require a significant investment.
 Glare-Direct sunlight penetration in classrooms and
office spaces often produces an unpleasant glare on
worksurfaces, making it difficult to work or view a
computer screen.
 Some architectural features, such as a building’s roof,
atrium shapes or a building’s angles, can prevent
daylight from illuminating a space.

5. orientation of
building
• The orientation of building is very important to achieve
maximum day light
• If the length of the building is oriented in an East-West axis, it
will allow penetration of passive heating or cooling within the
building
• A North-South façade is better as it allows penetration of good
day light by avoiding glare and over heating.
• Designers could decide which rooms need direct or indirect
sun-light and requirement of the quantity of heat loss or heat
gain

6. day-lighting in
tropics
HOT-DRY CLIMATES:
 Direct sunlight must be excluded from
buildings for the following reasons:
 Thermal
 Create glare
 Windows tend to be small – not much sky
will be visible from any point indoors –
hence SC (sky component) is insufficient.
 Ground & external surfaces of other bldgs.
are usually light coloured – in strong
sunlight these may create glare – hence ERC
can be used with provision to avoid glare.
 Internally reflected light – most convenient
form of daylighting.
 Suitable arrangement – high level window –
sill above eyelevel – would admit reflected
light to the ceiling.
 If the ceiling is white – above method would
ensure sufficient & well diffused interior
light through a small window.

7. WARM AND HUMID CLIMATE:
 Buildings in WARM AND HUMID climatic zone have:
 Large openings to ensure cross ventilation & air movement.
 Provided with wide overhanging eaves or shading devices.
 Direct sunlight is excluded – thermal reason - bright sky could
provide sufficient light - but its high luminance would cause glare
view of sky should be screened by shading device / plants.
 Sky luminance - less near the horizon than at higher altitude angles
- view of sky up to about 15⁰ may be permissible.
day-lighting in
tropics
Criteria for the design of shading
devices:
•Permit view of sky near the horizon
only. •Exclude view of bright ground
& sunlit blade / louvre surfaces.
•Daylight should be reflected from
ground & louvres to the ceiling –
ceiling should be of light colour.

8. concepts of day-
lighting
 WINDOWS AND SKYLIGHTS:
 The strategic installation of
skylights allows natural light to
enter a building through the
ceiling.
 As well, the installation of tall
windows allows outside light to
enter rooms more easily. The
placement of these windows
must be carefully considered to
minimize potential glare.
 Solar shading devices known as
overhangs can be used to
minimize the direct Sun that
enters the space.
There are numerous ways that sunlight can be used
advantageously inside buildings. Some traditional techniques to
improve natural lighting in buildings includes are listed below:

9. concepts of day-lighting
SKYLIGHT PLACEMENT AS A FUNCTION
OF BUILDING HEIGHT

10. concepts of day-
lighting CLERESTORIES : They are high windows with sill
heights greater than seven feet above the floor and are
excellent strategies for task illumination on horizontal
and vertical surfaces. Glass higher on a wall generally
provides deeper penetration into a room

11. concepts of day-
lighting ATRIA: They are central areas of
multi-storied buildings open to the
sky. Atria can be glazed to create a
controlled environment. Short and
wide atria perform better than tall
and narrow atria. Performance of
atria, like light wells, is dependent
on aspect ratio.

12.  SAWTOOTHS: They are apertures with vertical or
angled glazing installed in a slopped roof plane.
Saw- tooth's are most effective when used in series
of three and were historically used in industrial and
manufacturing buildings as the primary light source.
Sawtooth slope is generally at a 45 degree angle.
concepts of day-
lighting

13.  LIGHT SHELVES:A light shelf is
a horizontal surface that
reflects daylight deep into a
building.
 Light shelves are placed above
eye-level and have high-
reflectance upper surfaces,
which reflect daylight onto the
ceiling and deeper into the
space.
 Light shelves are typically used
in high-rise and low-rise office
buildings, as well as institutional
buildings. This design is
generally used on the equator-
facing side of the building,
which is where maximum
sunlight is found, and as a result
is most effective
concepts of day-
lighting

14. concepts of day-
lighting BUILDING DESIGN:
 There are numerous design changes
that can be made on buildings to
increase the amount of natural light
that can enter the building.
 One way to improve the amount of
natural light in a building is to build
with a shallow-plan design.
 This simply means buildings are
designed so that daylight can enter all
rooms and hallways, the building is
"shallow" enough that light can
penetrate all the way in.
 As well, the installation of task
lighting (lighting directly over work
spaces) can help reduce energy costs
as it reduces the need to light the
entire room.

15. concepts of day-
lighting LIGHT TUBES AND FIBRE OPTICS:
There are also a number of more experimental techniques being used
in an attempt to direct light into buildings.
 One of these methods is by using steerable mirrors to direct like
into areas it would not normally reach.
 As well, the use of optical fibres and light ducts to spread natural
light through a building is currently being experimented with.
 Light ducts are simply tubular devices that are coated with a
reflective film that channel light from the roof of a building to the
interior ceiling.
 They are beneficial as they are much smaller than skylights, but just
as effective.
 Fibre optic lighting devices send light through a bundle of optical
cables into a building using a physical mechanism known as total
internal reflection. This simply means that the light in the cables
bounces around on the inside of the cable, being transported as it
reflects.

16. DAY LIGHTING
THROUGH
LIGHT
TUBES
DAY-LIGHTING DUCT SYSTEM
It is more energy efficient than skylight since less energy escapes from the
interior due to less surface area.

17. design tools
 The location of the window(s) on the shorter or longer wall has to
be taken into consideration, as it influences the availability of
daylight at the centre of the room or nearby area.
 The relation between the daylight factor at the centre of a room
(or the rear of it, that is near the rear wall) and window are
expressed as a percentage of the floor area that will provide the
daylight factor is shown in graphs for four possible situations:
(a) the aperture is just an opening in the wall,
(b) the opening is glazed with 3 rom thick glass,
(c) the glazed opening is a wooden window, and
(d) the glazed opening is a metal window
(it is to be noted that a wooden window frame cuts off more daylight
as compared to a metallic window. frame).
 The sill height should be between 80 and 105 cm to get the
maximum advantage of vertical and horizontal plane illumination.
 The need to provide suitable louvers or overhangs to avoid direct
sunshine should be considered.
WINDOW DESIGN

18. DAYLIGHT AVAILABILITY AT THE
CENTRE OF A ROOM OR ITS REAR
ARE ASCERTAINED WITH
FOLLOWING ASSUMPTIONS
 The interior of the room possesses the
following reflection factors:
i) walls: 45-50 percent;
ii) ceiling: 70-75 percent; and
iii) floor: 24-30 percent.
 The combined thickness of wall and
width of louver is taken to be 60 cm;.
 The ground reflection factor is taken
as 0.25.
 The average daylight factor equation
can be used to estimate the require
window-to-wall ratio (WWR) for
adequate daylighting.
(Expressed as a fraction)
window design

19. principles of window design
GLARE is a visual sensation caused by
excessive and uncontrolled brightness. It can
be disabling or simply uncomfortable. It is
subjective, and sensitivity to glare can vary
widely. Older people are usually more
sensitive to glare due to the aging
characteristics of the eye.
Disability glare is the reduction in visibility
caused by intense light sources in the field of
view
Discomfort glare is the sensation of
annoyance or even pain induced by overly

20. day light factor
“PERCENTAGE RATIO OF THE INSTANTANEOUS ILLUMINATION
LEVEL AT A REFERENCE POINT INSIDE A ROOM TO THAT
OCCURRING SIMULTANEOUSLY OUTSIDE IN AN UNOBSTRUCTED
POSITION”.
COMPONENTS OF DAYLIGHT FACTOR:
The daylight factor is the sum of all the daylight reaching an indoor
reference point from the following sources:
 The direct sky visible from the point –SKY COMPONENT
 External surfaces reflecting light directly to the point –EXTERNAL
REFLECTED COMPONENT
 Internal surfaces reflecting and inter reflecting light to the point –
INTERNAL REFLECTED COMPONENT
DF = (Ei / Eo) X 100%
Ei – illuminance due to daylight at a point on the indoors working plane.
Eo – simultaneous outdoor illuminance on a horizontal plane from an
unobstructed hemisphere of sky.
2% OR 5% DF ARE 2 COMMON THRESHOLDS FOR DAYLIGHTING

21. deep
penetration
In a side-lit space with a standard window and
venetian blinds, the depth of the daylit area usually
lies between 1.5 and 2 time the window-head height.
If a space does not require the use of a shading
device the ratio can increase up to 2.5.

22. day-lighting in
interiors Using daylight or natural light for indoor illumination has
become the most popular and demanded application as it
is a very sustainable use of light, which not only reduces
electrical energy consumption, but also conserves it,
creates healthy indoor for any type of spaces.
 Daylight can be induced in residential spaces to office,
commercial and even hospitality interiors.
 The most important benefit of using daylight is it can
illuminate large part of an interior in an uniform way,
without any energy consumption .
 Sunlight kills many microbes and bacteria, keeping the
interior environment fresh, healthy and cheerful
 Using daylight reduces a lot amount of cost which is
usually spent on artificial lighting.

23. examples
PANTHEON, ROME
 the most visionary and fortunately the best
preserved Roman building, originally built
in 31 BC by the general and then mayor of
Rome, Agrippa, following a rectangular
layout.
 Hadrian rebuilt Pantheon in 125 AD in the
cylindrical shape.
 The interior of the Pantheon is an
impressive space due to its huge dome.
With its 44 m in diameter was two times
larger than any dome that had been built
before.
 The light falls from the great 8.9 m in diameter
central hole (oculus) in the top of the dome,
emphasizing the curve of the roof through a
play of light and shadow.
 Light travels 43 meters to symbolize the
connection of heaven with the earthly world.
The interior conveys a sense of grandeur and

24. examples
TOMOTHERAPY;
WISCONSIN Design Build was the primary force behind the promotion of day-lighting for
the TomoTherapy building as a means of improving energy efficiency and
helping to ensure occupant comfort.
 Of the 70,000 square feet of floor space in this building, 12,000 square feet
employ photo sensor-controlled dimming. Within this day-lit area, 22% of the
lighting energy is saved due to the dimming system.
DESIGN STRATEGY
 The building orientation is predominantly along a
north/south axis to fit onto the available land/site
configuration. This causes the majority of the
windows to face east or west.
 The window glass is all low-emissivity (low-e)
insulating glass. The bottom majority of the windows
or view windows are heavily tinted to reduce solar
transmittance and glare. The heavy tinting reduces
summer air-conditioning needs.
 The top sections of the windows are fitted with slightly clearer glass to allow
daylight to illuminate the office and assembly spaces. Solar transmittance is
24% and visible transmittance is 60%.
 The u-value for all windows is 0.30 BTU/hr/ft²/°F.
HEAVY TINTED AND
LOW E WINDOWS

25. examples Manual window blinds are employed to
reduce glare.
LIGHTING
STRATEGY The open office areas on the first and second floors
employ direct/ indirect Peerless lighting fixtures with a
single T5, high-output (HO), 54-watt, 4100 K lamp.
 General illumination levels logged over time and instantaneous readings
indicate highs of approximately 120 foot candles near windows on sunny
days to 17 foot Candles in interior spaces or near the windows on cloudy
days. Because of the higher-than-normal ceiling
height and the use of T5 HO lamps, the number
of lighting fixtures necessary for general
illumination is reduced from more prevalent
office lighting designs.
 Most private and semi-private offices have two
recessed, 2’ x 4’ parabolic light fixtures with
three T8, 4100 K lamps and electronic instant-
start ballasts. These lights are controlled through
a motion sensor with manual-on and automatic-
off functions.
 Hallways are lit with two-lamp, quad tube compact fluorescent down light
fixtures. Each compact fluorescent lamp is rated 26 watts.
 Observations during the evaluation and data logged on lighting energy usage
indicate these lights remain off until the evening hours.

26. shading
devices
 Sun Shading Devices inhibit the solar radiation(block, allow,, etc.)
incident on a building and are used either internally or externally or
in between the internal and the external building space.
 Types of shading devices:
a) internal
b) external
c) interpane
INTERNAL SHADING DEVICES
 Limit the glare resulting from solar radiation.
 Usually are adjustable and allow occupants to
regulate the amount of direct light entering their
space.
 CURTAINS: It is the most commonly used shading
device, mostly used on residential buildings.
 VENETIAN BLIND: basic slatted blinds made of metal or
plastic, wood or bamboo can also be used. Suspended
by a strip of cloth called tapes, all slats in unison can be
rotated through nearly 180 degrees. Slat width can be
between 16 and 120 mm, with 25 mm being a common

27. shading devices
 VERTICAL LOUVRE BLINDS: Suitable for
many applications in commercial and public
buildings where the control of heat, light
and glare are of concern. It can be used in
larger windows and doors too.
 ROLLER BLINDS: Roller
blinds are usually
stiffened polyester,
mounted on a metal pole
and operated with a side
chain or spring
mechanism.
 BLACKOUT BINDS: Blackout blinds stop light
from passing through thanks to special
treatments and extra tight woven fabrics to help
control the light levels in a room. It is designed
to block the external lights to enter the room.

28. shading devicesEXTERNAL SHADING DEVICES
 Considered better than internal
 TYPES: Horizontal, Vertical or inclined projections;
Vegetation and other buildings
HORIZONTAL DEVICES: to shade a window
during hot summer months, but to allow
sunlight to shine through a window in the
winter, to help warm a building.
VERTICAL DEVICES:
Primarily useful for east
and west exposures to
improve the insulation
value of glass in winter
months by acting as a
windbreak.THE EGG-CRATE: A combination of vertical
and horizontal shading elements commonly
used in hot climate regions because of their
high shading efficiencies. The horizontal
elements control ground glare from reflected
solar rays. The device works well on walls

29. shading devices
DESIGNING A SHADING DEVICE
 SELECT SHADING TYPE:
 IDENTIFY DESIGN DIMENSIONS:
Shading type: Horizontal Overhang
Shading category: fixed
Design dimensions: Relationship
between the overhang Depth (L) and the
opening height (H).
L=H; L=3H/4; L=H/2; L=H/3; L=H/4
Shading type: Vertical
Overhang
Shading category: fixed
Design Dimensions:
Relationship between the
overhang Depth (L) and the
opening width (d).
L=d L=3d/4 L=d/2
 IDENTIFY CATEGORY:
Fixed
Adjustable
Movable
Dynamic
Manual
Automatic

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