variables that might affect the sizing of such daylight apertures, e.g., the effect of the reflected component in clear sky
climates (DeKay and Brown 2014).
In this paper, the author tries to represent a quick tool to
determine the sizing of vertical windows for daylighting.
Unlike other studies, the proposed method of sizing vertical
windows could be characterized by being simple and more
generic.
The simplicity lies in describing the sizing of vertical
windows as a percentage of a single variable which is the
surface area of the room; floor area or total area of internal
surfaces, while being more generic because it is in the form
of a design chart, which in turn makes it applicable for any
location, i.e., city, within the low, middle, or high latitudes.
1.3 Main Objective and Hypothesis
The main objective of this paper is to introduce a simple
quick tool for architects, represented by two design charts
3
used to determine the sizing of vertical windows needed for
providing an adequate amount of daylight as a function of
the properties of the window, the room, and the surrounding
environment.
The main hypothesis of this paper is to investigate the
possibility of using a quick rule of thumb to find the surface
area of a vertical window for daylighting as a percentage of
the floor area or the total area of internal surfaces. This could
be done using the proposed design charts that use graphs
signifying most of the different variables that affect the
amount of daylight entering a given room. Those design
charts could be used for both design and analysis; design by
finding the surface area of the window needed to provide an
adequate amount of daylight, while analysis by calculating
the amount of daylight in a room resulting from the existence of a window or more with given surface areas.
2 Methodology
In this paper, in order to carry out the aimed design charts, a
number of calculation methods were used associated with
some simplifications and assumptions as follows.
2.1 Used Calculation Methods
Different calculation methods could be used for daylight
calculation and analysis; formula methods, graphical methods, scale models, and computer programs. Although
formula methods are not the most accurate daylighting calculation method, they could be used as a rule of thumb
especially within the preliminary stages of design. The
proposed design charts; the first and the second are derived
from the following formula methods one and two, respectively (Reid 1988).
Formula 1: W ¼
4 Â A Â DF%
s  h
Formula 2: W ¼
2 Â RA Â 1 À R
ð
ÞÂDF%
s  h
Those proposed design charts could be used by architects
as a simple quick tool for both design and analysis. They
could be used within the design process by finding the window area (W) needed to provide adequate amount of daylight
as a percentage of the floor area of the room (A), i.e., as a
ratio (W/A), as in the first design chart, or as a percentage of
the total area of the internal surfaces of the room (RA), i.e., as
a ratio (W/RA), as in the second design chart. Moreover, both
design charts could be used in the analysis of an existing case
by finding the available daylight factor (DF).
2.2 Simplifications and Assumptions
Some simplifications and assumptions are considered in the
first and second design charts concerning the effect of the
different variables and their applicability.
According to Corrodi and Spechtenhauser (2008), the
quantity of light provided by a window depends on different
variables. These variables involve the properties of the
window, the room, and the surrounding environment. Window properties include size, position, and shape. Room
properties include size and geometry, i.e., proportions of
length, width, and height. While surrounding environment
includes sky cover, amount of illumination, external
obstructions, and external reflectance (Kittler et al. 2012).
Effect of window position and shape. Both position and
shape of the window affect not only the distribution of
light along the depth of the room, i.e., the quality of daylight,
but also affects the quantity of daylight. But, since the design
charts are derived from formulas, those influences concerning the position and shape of window are neglected.
Effect of the geometry of the room. Both design charts
deal with surface areas, either the floor area (A) in the first
design chart or the total area of the internal surfaces (RA) in
the second chart. But none of them considered the effect of
the geometry of the room represented in its proportions and
ratios between length, width, and height that could be
described by a room index.
Effect of external obstructions. In both design charts the
effect of external obstructions is included within the chart
3
A chart is a graphical representation of data.
14
S. S. Saifelnasr
climates (DeKay and Brown 2014).
In this paper, the author tries to represent a quick tool to
determine the sizing of vertical windows for daylighting.
Unlike other studies, the proposed method of sizing vertical
windows could be characterized by being simple and more
generic.
The simplicity lies in describing the sizing of vertical
windows as a percentage of a single variable which is the
surface area of the room; floor area or total area of internal
surfaces, while being more generic because it is in the form
of a design chart, which in turn makes it applicable for any
location, i.e., city, within the low, middle, or high latitudes.
1.3 Main Objective and Hypothesis
The main objective of this paper is to introduce a simple
quick tool for architects, represented by two design charts
3
used to determine the sizing of vertical windows needed for
providing an adequate amount of daylight as a function of
the properties of the window, the room, and the surrounding
environment.
The main hypothesis of this paper is to investigate the
possibility of using a quick rule of thumb to find the surface
area of a vertical window for daylighting as a percentage of
the floor area or the total area of internal surfaces. This could
be done using the proposed design charts that use graphs
signifying most of the different variables that affect the
amount of daylight entering a given room. Those design
charts could be used for both design and analysis; design by
finding the surface area of the window needed to provide an
adequate amount of daylight, while analysis by calculating
the amount of daylight in a room resulting from the existence of a window or more with given surface areas.
2 Methodology
In this paper, in order to carry out the aimed design charts, a
number of calculation methods were used associated with
some simplifications and assumptions as follows.
2.1 Used Calculation Methods
Different calculation methods could be used for daylight
calculation and analysis; formula methods, graphical methods, scale models, and computer programs. Although
formula methods are not the most accurate daylighting calculation method, they could be used as a rule of thumb
especially within the preliminary stages of design. The
proposed design charts; the first and the second are derived
from the following formula methods one and two, respectively (Reid 1988).
Formula 1: W ¼
4 Â A Â DF%
s  h
Formula 2: W ¼
2 Â RA Â 1 À R
ð
ÞÂDF%
s  h
Those proposed design charts could be used by architects
as a simple quick tool for both design and analysis. They
could be used within the design process by finding the window area (W) needed to provide adequate amount of daylight
as a percentage of the floor area of the room (A), i.e., as a
ratio (W/A), as in the first design chart, or as a percentage of
the total area of the internal surfaces of the room (RA), i.e., as
a ratio (W/RA), as in the second design chart. Moreover, both
design charts could be used in the analysis of an existing case
by finding the available daylight factor (DF).
2.2 Simplifications and Assumptions
Some simplifications and assumptions are considered in the
first and second design charts concerning the effect of the
different variables and their applicability.
According to Corrodi and Spechtenhauser (2008), the
quantity of light provided by a window depends on different
variables. These variables involve the properties of the
window, the room, and the surrounding environment. Window properties include size, position, and shape. Room
properties include size and geometry, i.e., proportions of
length, width, and height. While surrounding environment
includes sky cover, amount of illumination, external
obstructions, and external reflectance (Kittler et al. 2012).
Effect of window position and shape. Both position and
shape of the window affect not only the distribution of
light along the depth of the room, i.e., the quality of daylight,
but also affects the quantity of daylight. But, since the design
charts are derived from formulas, those influences concerning the position and shape of window are neglected.
Effect of the geometry of the room. Both design charts
deal with surface areas, either the floor area (A) in the first
design chart or the total area of the internal surfaces (RA) in
the second chart. But none of them considered the effect of
the geometry of the room represented in its proportions and
ratios between length, width, and height that could be
described by a room index.
Effect of external obstructions. In both design charts the
effect of external obstructions is included within the chart
3
A chart is a graphical representation of data.
14
S. S. Saifelnasr