2. DEFINITION
In architecture, a daylight factor is the ratio of the light level inside a structure
to the light level outside the structure.
It is defined as:
DF = (Ei / Eo) x 100%
where,
Ei = luminance due to daylight at a point on the indoors working plane,
Eo = simultaneous outdoor luminance on a horizontal plane from an
unobstructed hemisphere of overcast sky.
3. There are three possible paths along which
light can get into a room through glazed
windows:
Light from the patch of sky visible at the point
considered, is expressed as the sky component
(SC),
Light reflected from opposing exterior surfaces
and then reached the point, is expressed as
the externally reflected component (ERC),
Light entering through the window but reaching
the point only after reflection from internal
surfaces, is expressed as the internally
reflected component (IRC).
4. Why day lighting comfortable and
attractive rather than artificial lighting?
Light emitted by the sun covers a wide spectrum of colors. The blend of these
colors makes up white daylight. Artificial light sources cannot exactly
reproduce the color spectrum of the sun. The eye senses this and reacts by
tiring more easily.
Daylight is dynamic. It varies through the seasons and times of the day, the
position of the sun and cloud cover. Artificial light is static.
A further advantage of daylight is its potential for energy saving. All
additional daylight not only means an increase in visual comfort, but also an
energy saving in artificial lighting
5. Issues to consider while providing
daylight
Shading and sun control
Visual requirements (glare, view, privacy)
Heat gains and losses
Thermal comfort
Condensation control
Ultraviolet control
Acoustic control
Security issues
Color effects
Energy requirements
Daylight performance
7. 1. Light Shelves
Increase Daylight Penetration.
Reduces the need for artificial
lighting in buildings.
Light shelves make it possible for
daylight to penetrate the space up
to 2.5 times the distance between
the floor and the top of the
window
Typical Light Shelf Sample
8. 2. Dynamic Light Shelves System
Shelves are movable so, direct light glare can be
prevented and also reaching of sunlight in to the deep
of the room is provided.
Two groups;
Manuel Systems: users arrange the positions of
the shelves according to seasons, months etc.
according to the sun’s position.
Automatic Systems: a micro computer arrange
the positions and angles of the shelves
according to seasons to provide efficient
illumination.
9. 3. Light Tubes
Emitting of daylight
from one optical staff
and transmitting to the
spaces.
This system is successful
at especially deep
spaces such as large
office buildings.
It is made up of three
parts;
Collector
(positioned on
rooftops. Hemi
sphere shaped
optics or a tube
take in or collects
the daylight.)
Transmitter
Distributer
10. 4. Fiber Optics
Fiber optics are, optical specified
fibers that can transmit and lead
the light rays even through the
long ranges.
Basic principle of fiber optic based
lightning is close to the light tube
systems.
Solar panels or heliostatic units
that are positioned on the roof
tops collect daylight that is
transmitted with fiber optic
cables, then daylight is transmitted
to light tubes. These tubes are
directly related with special
lightning source to illuminate the
spaces at day times.
Illumination with fiber optic system
11. 5. Anidolic Systems
Different from the light tubes, anidolic
systems do not collect the sun light.
Their work principle is; absorbing sunlight
with a glass semi optics unit than
transmitting to the ceiling system. In this
system there is no particular collector or
distributor.
Altough their simple mechanism anidolic
systems must be used with their special
ceiling systems, for this reason their field of
use is limited and sometimes that can be less
economical than the other systems.
