1. Prepared by
Dr. Nedhal Al-Tamimi
Arch. Eng. Dept.,
Faculty of Engineering
Najran University, KSA
naaltamimi@nu.edu.sa
Natural
Lighting
Lecture
No. 8
Climatic Design AE 353-2
2. Scope
of
Presentation
1. Introduction to Lighting
2. Principles of Natural Lighting
3. Variables Effect Illumination Level
4. Innovative Daylighting Technologies
5. Controlling Daylight
6. Daylighting Design Strategies
3. Introduction
Energy break-down:
▪ Visible light: 46-47%
▪ Near Infrared: 45%
▪ Ultraviolet (UV): 8-9%
For buildings in the tropics:
▪ Visible light welcome
▪ Infra red and UV light unwanted heat
4. Introduction
There are two principle ways in which a building
can be lit. These are:
Naturally - by daylight received from the sky.
Artificially - by electric lamps or other artificial
light sources.
Sunlight – That part of solar radiation
that reaches the earth’s surface as
parallel rays
Skylight – That part of solar radiation
reaches the earth’s surface and reflected
by (sky, tree, surface)
Daylighting is the controlled admission of natural
light : direct sunlight and diffuse skylight into a
building to reduce electric lighting and saving energy
5. Introduction
▪ Clear Sky with Direct Sun
▪ 100,000 lux perpendicular to the sun
▪ Intense, hot, glaring, highly directional
▪ Clear Sky without Sun
▪ 25,000 lux from the sky dome at noon
▪ Diffuse, cool
▪ Cloudy Sky
▪ 1,000 to 20,000 lux from the sky dome at noon
▪ Diffuse, cool
▪ Partly Cloudy Sky
▪ Some combination
SUN PATTERNS AND CONDITIONS
6. Natural Lighting (Daylight)
Definitions:
▪ That part of radiant energy from a hot body which produced the visual
sensation on human eye is called light.
▪ luminous intensity: The total quantity of radiant energy per second
▪ Lumen: Is the unit of luminous intensity.
▪ Daylight Factor DF: is the ratio of interior illuminance (Ei) to available
outdoor illuminance (EH) under overcast skies.
▪ Lux: is the unit of illuminance, measuring luminous flux per unit area
▪ Glare: is a visual sensation caused by excessive and uncontrolled
brightness. It can be disabling or simply uncomfortable.
7. Introduction
What is successful, sustainable daylighting design?
▪ Daylight as primary source of illumination
▪ Effective use of both solar and sky
components
▪ Providing a quality visual environment
▪ Integration with electric lighting system
▪ Appropriate control of natural light
▪ Energy savings by minimizing electric lighting
▪ Proper maintenance and operation
8. Introduction
Sample Energy Auditing for a
Governmental Building, KSA
Sample Energy Auditing for
a School Building, KSA
Daylight should become the primary light source in building for health,
productivity and sustainability.
Architects should design buildings to maximise the use of daylighting
Energy Savings With Daylighting
9. Natural Lighting (Daylight)
Characteristics of natural light:
▪ Free of charge (Natural source)
▪ Maintenance free
▪ Availability (daytime only)
▪ High variability (Daily / Seasonal) difficult to control
10. Variables effect the illumination level
Atrium Rooflight
Clerestorey
Borrowed light
Window
The quantity of daylight obtained within a room
will be dependent upon:
▪ Weather condition,
▪ Time
▪ Window’s orientation
▪ Size of glass
▪ Type of glass
▪ Far from window
11. Orientation for Daylighting
North & South windows can easily be
shaded by horizontal overhang
Direct Sun
▪ East-facing windows receive direct
sunshine during the morning, and
the same happens with west-facing
windows in the afternoon.
▪ For effective daylighting, the
number of windows facing east or
west should be minimized, and
sample use of shading is often
necessary to prevent glare and
excessive heating.
▪ In low-rise construction, it is often
possible to use trees for additional
shading. If the surrounding
buildings are taller, they also block
14. Type of glass
• Advanced glazing systems;
– Cut energy consumption,
– Avoid pollution sources,
– Reduce peak demand,
– Enhance daylighting performance,
– Improve occupant comfort.
One of the sample of vacuum based glazing system
16. The technologies available include:
Sunlight tracking systems - have mirrors
and/or lenses that follow the sun and redirect
its light to a required location.
− heliostat and light pipe systems.
− mirror systems.
Daylighting systems - redirect diffuse skylight
and usually sunlight as well. They generally
modify or supplement an existing window or
rooflight
A number of innovative daylighting technologies are available which are
capable of redirecting the incoming sunlight or skylight to the areas where
it is required.
Mirror system
Innovative Daylighting Technologies
17. SKY TUBE AS A NEW STRATEGY
Innovative Daylighting Technologies
18. Innovative Daylighting Technologies
LIGHTING SHELVES
▪ These can be used to redirect sunlight and skylight deep into a space.
▪ Both interior and exterior light shelves are available.
▪ Exterior shelves can also function as a shading device.
▪ The performance of light shelves depends upon the proportion of the
shelf which is situated inside or outside the space.
▪ They can also be used to control sunlight and reduce glare.
19. Innovative Daylighting Technologies
LIGHTING SHELVES
▪ Main goal; taking optimum level of sunlight to illuminate the
interiors of the buildings.
▪ This illumination is provided with small shelfs which act as
an illumination source.
Typical Light Shelf Sample
20. Controlling daylight
A range of methods are available to control the amount of daylight that penetrates
into the building.
▪ Fixed external – Permanently obstructs skylight and is maintenance free, but is
architecturally dominating.
▪ Variable external – Allows the maximisation of skylight but can suffer from
maintenance problems.
▪ Variable internal – Absorbs solar radiation and acts as a secondary heat source
within the building. Effective for visual comfort.
Various methods of controlling daylight
In addition, further control can be provided by the choice of glazing type.
22. Glare from daylight can be reduced by:
Adequate window orientation not only
limits heat gain, it also controls glare. By
minimizing the number of windows
facing east and west and using adequate
shading, glare is reduced significantly.
Using solar control devices - such as
external screens and louvres, glass of low
transmittance, or internal blinds and curtains
Other methods of decreasing the contrast
between the interior and the view of the sky
- such as ensuring that the window wall is light
coloured. Any surfaces or objects that can
reflect sunlight directly should be avoided
Controlling Glare
24. 1. Design consideration in different region.
2. Site design.
3. Orient the majority of the glazing north-south, with secondary
glazing to the west if necessary.
4. Building plan form.
5. Illuminate the ceiling as much as possible.
6. Protect against direct sunlight.
7. Balance light from the window wall with reflected daylight on
the opposite wall.
Daylighting Design Strategies
25. Daylighting Design Strategies
1. DESIGN CONSIDERATION IN DIFFERENT REGION.
Daylighting in the tropical region:
▪ Use shading –to prevent the transmission of the
direct sun beam.
▪ Avoid brightness from exterior surfaces that
reflects sunlight.
Daylighting in the arid region –hot & dry:
▪ Small windows
▪ High level of windows. (reflected from ceiling).
▪ Aperture opens to the Courtyard
26. Daylighting Design Strategies
2. SITE DESIGN (SKY EXPOSURE ANGLE.)
Site obstructions such as neighboring buildings, trees, and landforms will
determine the maximum available daylight on a site and the maximum
project envelope that will preserve daylight access to adjacent properties
27. Daylighting Design Strategies
3. BUILDING ORIENTATION
▪ Orient the majority of the glazing north-south, with
a maximum exposure to more easily controllable
daylight.
▪ South, is desirable because direct solar radiation
received by the south facade is easier to control to
prevent excess solar gain. Daylight is relatively
uniform.
▪ North light is the best for daylighting because it is
not direct and constant diffuse skylight. It is facade
is advantageous for uniform and soft daylighting.
▪ Toward the east and west the sun is very low—
almost horizontal—so it is hard to control.
28. Daylighting Design Strategies
4. BUILDING’S FORM
▪ Long and narrow footprints are better than
square one for access to daylight.
▪ Although square buildings have lower heating
loads, daylighting the interior is difficult.
▪ Multiple-story buildings benefit the most from
narrow plans that keep work areas within 10
meters of the exterior.
29. Daylighting Design Strategies
5. ILLUMINATE THE CEILING AS MUCH AS POSSIBLE.
▪ Clerestory windows should locate as high as
possible on the wall to illuminate the ceiling
and grab the maximum amount of daylight.
▪ The light shelf is an extremely useful to reflect
light falling above the vision window up onto
the ceiling .
30. Daylighting Design Strategies
6. PROTECT AGAINST DIRECT SUNLIGHT
▪ Direct sunlight should be blocked before it enters a space at certain
times of the year.
▪ Exterior louvers (horizontal or vertical), overhangs, trellises, trees,
and light shelves that can block direct sunlight, reflect diffused
sunlight into a space, and provide solar control
31. Daylighting Design Strategies
7. ROOM GEOMETRY
▪ The configuration of fenestrations has a
significant impact on the distribution of
daylight within a room.
33. Green Architecture
Next Lecture
9
1. Background
2. Why Green Architecture
3. Towered Green Architecture
4. What Green Building Seek to
Solve?
5. Green Building Rating System
6. Summary
