Content uploaded by Parham Kheirkhah
Author content
All content in this area was uploaded by Parham Kheirkhah on Dec 09, 2020
Content may be subject to copyright.
Available via license: CC BY-NC-ND 4.0
Content may be subject to copyright.
ARTICLE IN PRESS
JID: ENBENV [m5GeSdc; November 12, 2020;16:6 ]
Energy and Built Environment xxx (xxxx) xxx
Contents lists available at ScienceDirect
Energy and Built Environment
journal homepage: http://www.keaipublishing.com/en/journals/energy-and-built-environment/
Windcatchers and their applications in contemporary architecture
Parham Kheirkhah Sangdeh
∗
, Nazanin Nasrollahi
Engineering Faculty, Architecture Department, Ilam University, Ilam, Iran
Keywords:
Windcatcher
Wind tower
Badgir
Natural ventilation
Passive cooling
CFD
Natural ventilation and cooling have played an essential role in providing comfort conditions. Windcatchers are
passive cooling systems and one of the most familiar elements in Iranian architecture. They can signicantly
inuence on reduce cooling loads and supply the necessary ventilation rate of buildings. This paper aims at
providing an in-depth review of the recent developments and applications of windcatchers in modern architecture.
The eciency of windcatcher is also discussed according to the windcatcher’s relevant parameters, i.e., height,
conguration, and cross-section. This comprehensive review reveals that these factors have signicant impacts on
the performance of windcatchers. It is also shown that a one-sided windcatcher is a better choice in regions with
privileged wind direction. However, other types of it are better in regions with variable wind directions. Finally,
windcatchers’ potential for applying in the contemporary architecture and urban planning shown in the using
windcatcher in contemporary buildings, windcatchers in the urban context, new designs, and new technologies
of windcatchers sections.
1. Introduction
The building sector has a signicant proportion of total energy con-
sumption in various countries. Therefore, nding solutions for energy
saving inthis sector has a considerable impact on total energy consump-
tion [1] . The other main problem is air pollution, especially in big cities.
According to researches, the amount of CO2 from 1995 to 2018 be-
came three times. An important factor that aects air pollution is the
use of fossil fuels [2] . Natural ventilation reduces the use of fossil fu-
els [ 3 , 4 ]. Past generations found the solutions to be compatible with
nature [ 5 , 6 ]. In the arid and semi-arid regions, elements like wind-
catchers, courtyards, and domes have been used to attain a more com-
fortable condition [7–14] . Wind catchers (or wind towers) have been
used in the Middle-East countries (for example, more than one thou-
sand years in Iran, which is the origin of this technology [41] ) with dif-
ferent names and shapes [ 10 –12 ]. In Iran, windcatchers were common
spacially in hot and arid regions and called Badgir. They were decora-
tive as well as functional elements [15] . The most prominent examples
of traditional windcatchers are the windcatcher of Dowlat Abad garden
[16] , the Amirchakhmaq mosque’s windcatchers, and the windcatchers
of Alzubair’s historical city [ 11 , 12 , 17–19 ]. Although windcatchers are
useful, the architecture and lifestyle changes need modern wind catchers
with new designs [20–23] . The new windcatchers should be harmonious
with new architecture in any aspect and also be more controllable and
exible. The mechanism of modern and traditional windcatchers is the
same. The traditional windcatchers provided comfort conditions in two
∗ Corresponding author.
E-mail address: parham.kheirkhah@gmail.com (P.K. Sangdeh).
ways. The traditional houses in the arid areas have two main parts: the
southern part where inhabitants dwelled in cold seasons, and the north-
ern part where residents inhabited in warm seasons. The windcatchers
have been positioned in the north part facing and catching cold north-
owing winds to fulll maximum ventilation and cooling [24–28] . In
some cases, Qanat increased the evaporating cooling, decreasing tem-
perature, and increasing humidity, velocity, and density of incoming
airow and eventually improving windcatchers’ performance [29–31] .
Evaporating cooling has been used in some modern windcatchers, but
using it depends on climate [ 32 , 33 ]. The second mechanism has been
utilized when the wind velocity is low. In this condition, indoor air has
been sucked into outdoor space. In this way, the windcatcher has at-
tributes of the solar chimney and used buoyancy forces [ 24 , 34 ]. Be-
tween two main forces impacting windcatchers’ eciency, wind-driven
power plays a more critical role than the buoyancy force [ 35 , 36 ]. Nowa-
days, with advanced and accurate software and calculative formulas,
achieving a general understanding of windcatchers, their process, and
the factors which impact their performance are more feasible than in
the past [ 37 , 38 ]. This realization is the rst step for designing an e-
cient and ideal modern windcatcher [39] . In this paper, the rst stage
tries to obtain comprehensive knowledge about types and congurations
of windcatchers. This knowledge helps to understand new ideas about
windcatchers and new technologies applied to them, mentioned in the
second stage. The last step is about using modern windcatchers in build-
ings. This use indicates that modern windcatchers have high potential to
be a pretty decorative element, an ecient natural ventilation device.
https://doi.org/10.1016/j.enbenv.2020.10.005
Received 29 September 2020; Received in revised form 25 October 2020; Accepted 27 October 2020
Available online xxx
2666-1233/© 2020 Southwest Jiaotong University. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
( http://creativecommons.org/licenses/by-nc-nd/4.0/ )
Please cite this article as: P.K. Sangdeh and N. Nasrollahi, Windcatchers and their applications in contemporary architecture, Energy and Built
Environment, https://doi.org/10.1016/j.enbenv.2020.10.005
P.K. Sangdeh and N. Nasrollahi Energy and Built Environment xxx (xxxx) xxx
ARTICLE IN PRESS
JID: ENBENV [m5GeSdc; November 12, 2020;16:6 ]
1.1. Literature review
There are many papers about various aspects of windcatchers. How-
ever, there are some issues that the number of researches about them is
few. For example, the number of researches about the impact of mate-
rial, height, and neighborhood on the performance of windcatchers and
the economic benets of using windcatchers is not signicant. Table 1
shows the number of investigations carried out on windcatchers.
Fig. 1 shows the proportion of any topics about windcatcher. If “Fac-
tors which impact on the performance of windcatcher ”are considered as
a topic, according to this gure, it has the most portion of the investiga-
tions about windcatcher (25 percent), and surveys about the economic
aspect of using windcatcher have the lowest proportion (2 percent).
Fig. 1 shows the focuses of researches have been on modern wind
catchers instead of traditional windcatchers. Rezaeian et al. [40] , in
their study, conrm this. Since the year 2000, they have expressed the
focusses of studies that have been changed from traditional windcatch-
ers to the development of innovative windcatcher systems. Fig. 2 shows
the number of articles in dierent decades. According to this gure, the
number of items about windcatchers increases in the 2010s. This in-
Table 1
Number of investigations about various aspects of windcatcher.
Topics Frequency
Types of windatcher 10
Methods for evaluating the performance of windcatcher 12
Performance of windcatcher 21
The economic aspect of using windatcher 2
Factors which impact on the
performance of windatcher
Number of
openings
7
Height of
windatcher
4
Wind approach 10
velocity 6
configuration 8
Architectural solutions for improvement Efficiency of
windcatchers
3
New designs for windcatcher 38
Using windcatchers in contemporary buildings 10
New technologies of windcatcher 19
windcatchers in urban context 9
crease indicates that nowadays, windcatchers are essential and have a
high potential for modern societies.
Rezaeian et al. [40] explain the procedure of researches about wind-
catchers. According to their investigation, research about windcatchers
started in 1984. A signicant increase in the number of articles occurred
in 1990. It reached its saturation level in 1997. After the year 2000,
by appearing CFD (Computational Fluid Dynamic) number of research
increased. This growth has continued until today. Rezaeian et al. fore-
casted number of researches about windcatchers will arrive at 142 pa-
pers.
2. Types of windtchers
Windcatchers have various kinds. Windcatchers have been classied
into dierent groups, including numbers of openings, number of stores,
cross-section, and interior dividing [41] . Table 2 shows these classica-
tions.
2.1. Types of windcatchers according to the number of openings
Windcatchers, according to the number of openings classied to
[42] :
- One-sided windcatchers
- Two-sided windcatchers
- Four-sided windcatchers
- Six-sided windcatchers
- Eight-sided windcatchers
One-sided windcatcher has an inlet incoming the north direction
and has no opening in the east, west, and south, bringing cold north-
ern winds into indoor spaces [41–43] . This type of windcatchers can be
found in Ardakan and Maybod [42] . However, just 3 percent of wind-
catchers in Yazd is one-sided. One-sided windcatchers are more resistant
to the storm than other types of windcatchers [44] . Respecting dimen-
sions, two-sided windcatchers are smaller than one-sided windcatchers.
Two-sided windcatchers called twin windcatchers too [45] . For divid-
ing them into two separate parts, brick blades are used. Roaf [46] states
that 17 percent of windcatchers in Yazd are two-sided, and all of them
were used for wealthy people, but Bahadori [40] says most of them were
used for storage of water (Ab-Anbar). Four-sided windcatchers are taller
and bigger than others. Usually, these windcatchers have been used in
Fig. 1. Proportion of all relevant topics with regard to the windcatcher.
2
P.K. Sangdeh and N. Nasrollahi Energy and Built Environment xxx (xxxx) xxx
ARTICLE IN PRESS
JID: ENBENV [m5GeSdc; November 12, 2020;16:6 ]
Fig. 2. Number of papers about windcatchers in dierent decades.
Table 2
Dierent types of windcatchers in various aspects [45] .
areas with desert-like climate. Their heights are varying according to cli-
mate conditions [43] . Four-sided windcatchers are the prevailing type
[47] . All of the windcatchers in hot and humid areas are four-sided.
Eight-sided windcatchers usually have been used for water storage, and
roughly 2 percent of Yazd’s windcatchers are from this type [ 43 , 46 ].
2.2. Types of windcatchers according to the cross- section
Windcatchers classied into ve main groups based on their cross-
section [42] :
- Cylindrical windcatchers
- Square windcatchers
- Rectangular windcatchers
- Hexahedral windcatcher
- Tetrahedral windcatchers
Table 2 illustrates the classication of windcatchers according to the
cross-section. Construction of cylindrical windcatchers is more compli-
cated than square, rectangular, and even tetrahedral and hexahedral
cross-section windcatchers. Therefore, cylindrical windcatchers were
not too common comparing to the others. However, designing cylindri-
cal windcatchers is based on winds’ aerodynamic characteristics, so they
have high eciency [42] . Square windcatchers are more common than
those with the circle, hexahedral, and tetrahedral cross-section. How-
ever, windcatchers with rectangular cross-sections are the most con-
ventional type of windcatchers [42] . Hexahedral and tetrahedral wind-
catchers are shorter than the other types and usually were used for water
storage [ 43 , 46 ].
2.3. Types of windcatchers according to number of stores
Windcatchers are one-story, two-story, and scarcely have more sto-
ries. The number of two-story windcatchers is remarkably lower than
one story windcatchers and even considered as scarce types. Several
outstanding samples of two-story windcatchers are in Amir Garden in
Tabas city (eight-sided), in Aghazadeh House in Abarkooh (four-sided),
in Chehel Sotoon in Sarhanabad (cylindrical) [42] . In addition to one
and two-story types, there are some with more stories. For example,
3
P.K. Sangdeh and N. Nasrollahi Energy and Built Environment xxx (xxxx) xxx
ARTICLE IN PRESS
JID: ENBENV [m5GeSdc; November 12, 2020;16:6 ]
Fig. 3. Dierent types of square windcatchers in aspect of internal dividing
[45] .
Fig. 4. Internal dividing of six-sided and eight-sided windcatchers [45] .
a windcatcher in Sadra Garden in Taft is three-story. However, wind-
catchers with more stories are scarce, and ignoring them is possible.
The one-story windcatchers are the most frequent [42] .
2.4. Types of windcatchers according to positions of blades
Interior blades play an essential role in the eciency of windcatch-
ers. They divide the cross-section of windcatchers into smaller parts
and consequently impact the velocity and turbulence of airow. There-
fore, windcatchers with dierent types of division have various features,
aecting windcatcher performance. Windcatchers with square cross-
section have four kinds of divisions illustrated in Fig. 3 [48] .
Each of the windcatchers with tetrahedral and hexahedral cross-
section has one division. In these divisions, blades are connected to the
tip of the tetrahedral and hexahedral. Fig. 4 illustrates these types [48] .
The dierent shapes of blades in the rectangular windcatchers are in-
cluding X shape blades, + shape blades, and H shape blades. Fig. 5 shows
a rectangular windcatcher with X shape blades. The ratio of height to
width in these windcatchers are 1.5. The number of this type is insignif-
icant. In the study of Amirkhani et al. [43] from 58 investigated wind-
catchers, just 2 of them have X-shaped blades. Sometimes, K-shaped
blades appear for dividing. It’s a combination of + and X-shaped parti-
tions [49] .
Fig. 6 shows a Rectangular windcatcher with + shape blades. This
type is the most frequent type of dividing [50] .
The number of windcatchers with H-shaped blades is scanty. Fig. 7
illustrates this type. The principal blade is placed in the center of the
channel [43] .
Table 2 shows the various classications of windcatchers with dif-
ferent aspects.
3. Methods for evaluating the performance of windcatchers
Methods for assessing the performance of windcatchers have been
classied into two groups. To fulll this purpose, both experimental and
theoretical techniques are useful. However, each of them has its pros
and cons. The experimental method has two types. In the rst type, a
scaled model has been built and investigated in a lab, and the second
type (eld measurements) has been used to investigate a real model
in a real condition, so the results are more reliable. However, scaled
models are more money and time saving than the eld measurements,
and more importantly, a generalization of results to other conditions can
be achieved [ 15 , 51 , 52 ]. Moreover, changes in various parameters are
possible easily. Therefore, each parameter’s eect on the windcatcher’s
performance can be revealed, but this process in the eld measurements
is impossible [ 15 , 53–55 ].
Fig. 5. Rectangular windcatcher with X shape blades [45] .
Fig. 6. Rectangular windcatcher with + shape blades [45] .
4
P.K. Sangdeh and N. Nasrollahi Energy and Built Environment xxx (xxxx) xxx
ARTICLE IN PRESS
JID: ENBENV [m5GeSdc; November 12, 2020;16:6 ]
Fig. 7. Rectangular windcatchers with H shape blades [45] .
Fig. 8. Proportion of applying dierent methods in the papers about windcatch-
ers.
3.1. Simulation
The theoretical investigation has been classied into two groups: an-
alytical and numerical modeling. Analytical modeling is a fast way to
discover the performance of windcatchers. Still, this method can’t solve
unforeseen conditions because it only uses heat transfer and uid dy-
namics formulas. For instance, a rotary thermal wheel’s rotation speed
that has a signicant impact on windcatcher performance can’t be cal-
culated in analytical modeling [ 15 , 56 , 57 ]. Numerical modeling consists
of software simulations of real conditions for models. This kind of soft-
ware works based on principles of computational uid dynamics (CFD).
CFD can see various factors (temperature, velocity, pressure) in compli-
cated three-dimensional ows [ 15 , 58 , 59 ]. In the mentioned methods,
numerical modeling is more conventional ( Fig. 8 ).
In numerical modeling, simulating dierent conditions for investi-
gating various parameters is easily possible [60] . Table 3 shows the ap-
plied settings in the research.
In a simulation (numerical modeling), there are many parameters,
each of which signicantly impacts results [70] . Therefore, selecting
these parameters needs essential knowledge and accuracy. For exam-
ple, turbulence is a crucial factor aecting outcomes [ 71 , 72 ]. Fig. 9
illustrates the impacts of these parameters on the results of the simula-
tions.
4. Performance of windcatcher
Windcatchers have more advantages than other openings
[ 65 , 73 , 74 ]. In a dense urban context, the windows’ eciency is
low, and windcatchers can be an ecient superseded solution for sup-
plying the required ventilation rate here. Drach’s [75] has researched
a three-story house with inadequate natural ventilation. The results
of this paper indicate that adding a windcatcher improved natural
ventilation in this house. Another advantage of windcatcher rather than
other openings is the higher pressure coecient (CP). The ventilation
rate depends on the pressure coecient at the opening [76] . Table 4
Shows CP for windcatchers and other openings in rural and open areas
in various wind approaches. This table’s results indicate that CP for
windcatcher is higher than other openings [ 42 , 77 ].
Montazeri et al. [69] have measured CP for one-sided and two-sided
windcatchers through a wind tunnel experiment. This investigation and
the research by Bahadori show a higher performance of windcatchers
( Table 5 ).
Sadeghi et al. [78] studied a windcatcher’s performance in the urban
context of Australia and compared it with ventilation through windows.
Results of this study indicate that:
- The pressure dierence between the inlet (windcatcher) and outlet
(window) and vice versa was three-time of pressure dierence when
the window was used for ventilation.
- The average internal airow velocity in the six warm months of Syd-
ney in the case with an optimized windcatcher was three-time higher
than the case of window ventilation.
One of the windows’ limitations is that they aren’t usable in base-
ments, but windcatchers are useful in these underground spaces. Roaf
[27] has investigated Khan Garden in Yazd. In this place, there is a
living room in the basement connected to a windcatcher that crosses
on a Qanat owning a 50-meter-long tunnel. The investigation indicates
that when the exterior temperature was 40°C, the interior temperature
was 25°C. Moreover, the eects of windcatchers on increasing veloc-
ity and decreasing interior spaces’ temperature can reduce the uctu-
ations of temperature [79–81] . Priya et al. [82] investigated a house
with a balcony and windcatcher. While uctuation of exterior temper-
ature was 11°C, uctuation of interior temperature was 3°C, and while
uctuations of exterior temperature were 16°C the oscillating of internal
temperature was 5°C. In the investigation of Ghadiri et al. [83] , wind-
catchers can decrease the interior temperature 3°C - 5°C compared to
the exterior environment during the daytime, but at night, the internal
temperature was 3°C - 4°C higher than the outer environment. Sadeghi
et al. [84] investigated windcatchers’ performance for an apartment in
Sydney humid climate. In this case, mean air velocity, incoming by a
windcatcher, was as three-fold as mean air velocity, which income by
a window to meet thermal comfort needs. Studies of Mohammadi and
Barzegar [85] and Kistelegdi et al. [86] conrms the decisive role of
windcatchers in providing thermal comfort conditions. Therefore, de-
spite windcatchers’ limitations, they can increase velocity and decrease
the interior temperature in hot climates for achieving comfort conditions
[87] . Therefore, today windcatchers are an ecient cooling passive sys-
tem that can help reduce the cooling loads in contemporary buildings
[84] . Adding evaporative cooling to windcatchers improves their func-
tion and indoor conditions [ 32 , 33 , 88–91 ].
5. Economic aspect of using windcatcher
One of the most critical factors for evaluating a system’s usefulness
is the economy [92] . For comparing and assessing various systems, the
formula below has been used.
5
P.K. Sangdeh and N. Nasrollahi Energy and Built Environment xxx (xxxx) xxx
ARTICLE IN PRESS
JID: ENBENV [m5GeSdc; November 12, 2020;16:6 ]
Table 3
Dierent parameters and methods used in papers about windcatcher ( E: Expriment, N: Numerical modeling, A: Analytic modeling, DECT: down-draft evaporative cool
tower, T: Traditional windcacther, TIW: Traditional windcatcher integrated a wingwall, CW: commercial windcatcher, ABL: atmospheric boundary layer, Uniform:
uniform inlet velocity, 3D: three-dimensional, C: coupled outdoor-indoor simulations).
Author (year) Ref Method
Number of
openings Type
Turbulence
Modeling Mesh Inlet prole
Dimension/
coupling
Sensivity
analysis Subject
Erell et al.
(2008)
[61] E 1 DECT - - - - - Thermal performance and flow
rate of DECT
Afshin et al.
(2016)
[62] E 2 T - - - - - Performance of windcatcher in
various wind angles and wind
speed
Nejat et al.
(2016)
[63] E/N 2 TIW standard k-e Non-uniform ABL 3D/C Grid Anti-short circuit device
performance
Calautit et al.
(2015)
[39] E/N 1 CW standard k-e Non-uniform uniform 3D/C Grid Performance of a standard
windcatcher and HTD
windcatcher
Mak(2010) [64] N 4 CW standard k-e unstructured
grid
uniform 3D/C - The function of the
windcatcher quadrants
in
various wind directions and
speeds
Montazeri
et al. (2008)
[65] E 1 T - - - - - Effect of placing of urban
windcatchers in the boundary
layer of atmospheric winds
Dehghan et al.
(2013)
[66] E/A 1 T - - - - - Impact of roof shape on
windcatcher performance
Hosseinnia [67] N 4 T Standard k-e Unstructured
tetrahedral
cells
ABL 3D/C - Impact of Various blades on
performance of windcatcher
Kalantar (2009) [30] N 4 T Stan dard k-e Unstr ucture d Unifo rm 3D/C Grid Impact of evaporating cooling
Ghadiri et al.
(2014)
[68] N 4 T Standard k-e Structured
hexahedral
and
prism
ABL 3D/C Grid The effect of plan size of
windcatchers on its ventilation
rate
Montazeri
et al. (2010)
[69] A/N/E 2 T Standard k-e RNG
k-e Reynolds Stress
model
Unstruc tured/
structured grid
uniform 3D/C - Performance of two-sided
windcatcher
Fig. 9. Assessing velocity inside a windcatcher with dierent turbulent models. a: k-e Realizable. b: k-e RNG. c: standard k-e. d: sst k-omega. e: sst k-omega. f:
streamline built by PIV [72] .
Table 4
Pressure coecient for windcatcher and other openings in dierent wind angles and areas. WC: windcatcher,
O.O: other openings.
Areas The angle between wind and inlet
0° 45° 90° 120° 150° 180°
W.C. O.O W.C. O.O W.C. O.O W.C. O.O W.C. O.O O.O
Rural area 0.53 0.04 0.43 0.12 0.66 0.35 0.50 0.35 0.54 0.25 0.61 0.25
Open area 0.54 0.12 0.43 0.18 0.71 0.33 0.53 0.32 0.55 0.38 0.61 0.32
Economic eciency = operation/ (producing cost + using cost + ex-
ternal cost)
Therefore, enhancing economic eciency depends on decreasing
costs. Solutions like combining architectural techniques with climatic
strategies and renewable energy systems signicantly reduce these costs
[93] . MostafayiPour et al. [93] , for evaluating windcatchers’ economic
eciency, selected a warehouse with dimensions of 10 m, 14 m, and 50
m. They considered three scenarios for this research:
1- Ground oor level, cooling by an absorption chiller 2- Basement
level
6
P.K. Sangdeh and N. Nasrollahi Energy and Built Environment xxx (xxxx) xxx
ARTICLE IN PRESS
JID: ENBENV [m5GeSdc; November 12, 2020;16:6 ]
Table 5
Comparing Pressure coecient for one-sided windcatcher, two-sided wind
catcher, and other openings in dierent wind angles.
Wind
angles
Two-sided windcatcher One-sided
windcatcher
Other
openings
Windward Leeward
0° 0.86 -0.36 0.81 0.12
45° 0.21 -0.37 0.38 0.18
90° -0.49 -0.46 -0.30 0.33
135° -0.37 0.21 -0.38 -0.38
180° 0.036 0.86 -0.43 0.32
3- Basement level, cooling by windcatcher
The results of this study indicate that the scenario with wildcatter
was most ecient practically and economically.
6. Factors which impact on the performance of windcatchers
There are many factors which have a signicant impact on the per-
formance of windcatcher. These factors can be internal like cross-section
and height of windcatcher or external like velocity or wind angle [90] .
6.1. Number of openings
The number of openings is one of the most critical factors contribut-
ing to windcatchers’ eciency [94] . Dierences in the number of open-
ings lead to dierences in features of various kinds of windcatchers.
Therefore, each kind of them is ecient in a particular region with spe-
cial climatic conditions. For example, two-sided windcatchers act like
one-sided windcatchers. One side of them can bring fresh cooled air to
indoor space, and another part can act like a chimney and suck indoor air
to exterior space at the same time. One-sided windcatchers have not this
feature [95] . On the other hand, in several windcatchers with equal di-
mensions, windcatchers with fewer openings bring air for indoor space
with a higher rate. Montazeri [96] , in one of his studies, investigated
one windcatcher with a cylindrical cross-section and dierent numbers
of openings. He divided the cross-section of windcatchers into 2, 4, 6,
and 12 sections and compared the eciency of them in experimental
conditions with each other. The results of this experiment indicate that
a two-sided windcatcher had the best performance. On the other hand,
the more openings a windcatcher has, the fewer eects wind angles have
on the entering ow rate. Therefore, in areas with the one-direction
prevailing wind, the one-sided windcatchers are preferred to the others
from an economical and technical perspective. This is because, in a one-
sided windcatcher, all of the cross-sections act as the entrance of airow,
but in two or more-sided half or less of cross-section, bring airow to
indoor spaces [ 69 , 97 , 98 ]. In addition to the number of openings of a
windcatcher, the building’s openings aect this vein in terms of area,
location, and distance from the windcatcher [99] .
6.2. The height of windcatcher
Height is an eective factor for the performance of windcatcher by
two parameters. First, the height of the windcatcher and second, the
ratio of windcatcher height to the neighborhood’s building height. De-
termining an optimal height for a windcatcher depends on the climate,
type of windcatcher, and cross-section. The eects of these parameters
have been shown in dierences between Ghadiri [100] and Badran’s
[101] article results. Ghadiri [95] investigated a windcatcher with H-
shaped blades and dierent height in Yazd city climate. Assumed heights
for this windcatcher were 3.5 to 10.5 meters. She assumed 5 meters per
second for the velocity of airow and 37°C for air temperature. At the
same time, Badran [101] investigated a windcatcher in Aman (capital
of Jordan). The cross-section of this windcatcher was 1m2, and Badran
used evaporative cooling in it. Badran investigated windcatchers with
heights between 0 to 9 meters. He computed optimum height in mathe-
matical formulas. Consequently, Badran deduced 9 meters is the optimal
height for windcatchers. The results indicate that increasing height up
to 9 meters improves the performance of windcatchers, and after that,
this improvement will be insignicant. Therefore, in his opinion, the
optimal height is 9 meters. Whereas, Ghadiri deduced 6 meters for the
optimal height for windcatchers. Ismail investigated windcatchers with
dierent heights (3, 6, and 9 meters) integrated with a classroom. Re-
sults indicate that with increasing height, the performance will improve.
However, the eciency of windcatchers with 6 and 9-meter height was
close to each other. From economic and aesthetic points of view, 6-m
height has been considered the optimum height for windcatchers [102] .
Sheikhshahrokhdehkordi et al. [103] investigated the windcatchers
of dierent height. According to the results, increasing the height leads
to a decrease in the mass ow rate.
The other factors are the distance (density) and the height of neigh-
bor buildings. It has a signicant impact on the eciency of wind-
catchers [104] . For determining the level of this eect, Afshin et al.
[105] performed a study where a windcatcher-integrated building was
investigated along with the neighbor buildings with dierent heights.
The results of this study indicate that the existence of a building with
low height in the neighborhood (with a height of 0.5 H of windcatcher
and distance of 0.75 H of windcatcher) can increase the ventilation rate.
However, the existence of higher buildings has a reverse eect. In this
condition, both shafts of two-sided windcatcher act as a chimney and
suck air of indoor to outdoor space.
6.3. Wind approach
Wind direction is eective on introduced pressure on opening, lee-
ward, and windward sides. Pressure dierence on the surfaces plays an
important role in supplying the needed airow rate. For a windcatcher,
most pressure coecient and airow rate occur at a 0° wind angle. The
angles between 0° and transition ventilation rate gradually decline with
increasing wind angle [ 62 , 64 , 69 , 98,106–110 ]. At the transition angle,
the supplied airow goes to zero. Afshin et al. [62] have introduced it
55°, and Montazeri and Azizian [76] introduce it between 50°- 60°. The
minimum ventilation rate occurs in the transition angle. In higher an-
gles, two shafts of two-sided windcatchers act reversely [75] . According
to the MAK [64] study, in four-sided windcatchers between 0° and 15°
of wind angles, just one side bring airow to indoor spaces. At 30° and
45° wind angle, two shafts have this function. At 0° to 10° and higher
than 40°, as wind angle increases, airow rate decreases, and at the wind
angles between 10° to 40°, increasing in wind angle leads to an increase
in the airow rate.
6.4. Velocity
Increasing velocity will increase the ventilation rate in windcatcher-
integrated buildings [110–113] . However, the question is that level of
this increase would be the same for all wind angles? MAK [64] carried
out a study about the performance of a four-sided windcatcher at 0°, 15°,
30°, and 45° wind angles. The windcatcher at 45° wind angle had the
most sensitivity and had less sensitivity toward velocity at 0° wind an-
gles. That means the 45° wind angle increasing in velocity causes to an
increase in the airow rate more than other wind angles. At 0° wind an-
gle, increasing velocity causes an increase in the airow rate less than
other wind angles. Another question is if increasing velocity is bene-
cial in all kinds of windcatchers? Calautit et al. [114] have studied
wind tower integrated with heat transfer devices. While the outdoor
ow speed was 5 m/s, the reduction in indoor space temperature was
5°C, but when the outdoor velocity was 1-2 m/s, this reduction reached
9.5 – 12.
6.5. Configuration
Conguration factors like cross-section dimensions, arrangements
of interior blades, and roof shape have been investigated in this part.
7
P.K. Sangdeh and N. Nasrollahi Energy and Built Environment xxx (xxxx) xxx
ARTICLE IN PRESS
JID: ENBENV [m5GeSdc; November 12, 2020;16:6 ]
It’s evident that with an increase in cross-section (it means that the
opening dimensions will increase too), the amount of airow will in-
crease. But other factors aren’t as simple as dimensions and shape
of cross-section. Each of these factors is very eective in the perfor-
mance of windcatchers. Therefore, designing an optimum windcatcher
needs studying these factors for obtaining the best combination for
windcatchers [115] . Farouk [109] compared the square, Hexagon, and
circular six-sided windcatchers in various velocities and wind angles.
The average incoming airow rate in the hexagon windcatcher was
19 percent more than the square windcatcher. Moreover, the hexagon
windcatcher had lower sensitivity to wind angles than the square
windcatcher.
However, a 0° wind angle case with the square windcatcher has a
higher mean velocity than the hexagon windcatcher in indoor space. The
circular six-sided windcatcher had the lowest mean speed. Therefore, at
a 0° wind angle, the square windcatcher is more eective for making
thermal comfort conditions. Jafari et al. [108] compared two models of
four-sided windcatchers. One of them had a square cross-section with
X-shaped blades, and another was a circular four-sided windcatcher.
They studied these models in various wind angles. In the square model,
whirlpool was less than the other models. Therefore, they concluded
that sharp edges could be a reason for whirlpool reduction, a broad
region of ow separation, more pressure dierence, and nally, more
ow induction.
Results of an investigation by Sheikhshahrokhdehkordi et al.
[103] indicate that cross-section changes lead to changes in windcatch-
ers’ eciency. There are various arrangements for blades of four-sided
windcatchers include X, K, + , and H. Dierent articles have compared
these shapes with each other through dierent indicators: the potential
of decreasing indoor temperature. Ghadiri et al. [115] made a compar-
ison between two windcatchers with K and X-shaped of blades with the
same dimensions and conditions ( Fig. 10 ). This research indicated that
windcatcher with X-shaped blades could bring airow with a lower tem-
perature to indoor space.
Dehnavi et al. [116] compared windcatchers with + , X, H, and K-
shaped blades of windcatchers ( Fig. 11 shows these blades). The ref-
erence case was a windcatcher with a crosssection of 1.5 m
∗ 1.5 m
and height 8 m. Results indicate that a windcatcher with a + shaped
blade has less potential for decreasing indoor temperature. After that,
windcatchers with K, H, and X-shaped blades have superior potential,
respectively.
Zarandi [49] compared dimensions of windcatchers owning three
types of blades (shown in Fig. 12 ) through CFD with dimensions of
windcatcher of Rasolian house. Indicators in this research were relative
humidity, temperature, and velocity of airow. According to the results,
a windcatcher with + shaped blades was more ecient than other cases.
The roof’s impact has been investigated in the research of Dehghan
et al. [66] . They considered three roofs (sloped, at, and curve roof)
with various wind angles. In 0° wind angles, the windcatcher’s eciency
with the curved roof was 10 and 4.5 percent higher than a at roof and
sloped-roof windcatcher, respectively. However, the windcatcher with
a sloped roof had the lowest sensitivity to changing the wind angles.
Another parameter that impacts the performance of windcatchers in the
shape of the inlet. Abdo et al. [117] considered three forms for inlet
of windcatchers (uniform inlet, bulging-converging inlet, and divergent
inlet) and compared them in a study. Results indicated that this param-
eter has a signicant eect on eciency. Between these three cases,
a windcatcher with a divergent inlet has the best performance. In wind
velocity of 6m/s, the average velocity of cached airow for windcatcher
with divergent inlet was 8.44 percent higher than windcatcher with the
bulging-converging inlet.
Varela-Boydo et al. [118] investigated 33 models of the outlet open-
ing of windcatchers. They tried to guide designers in designing wind-
catchers with higher eciency. This investigation shows that shape,
size, and position of outlet opening have a signicant impact on the
performance of windcatchers.
Table 6 expresses briey various parameters impacting the perfor-
mance of windcatchers and their conclusion.
7. Architectural solutions for improvement of windcatchers
performance
Architectural solutions to improve windcatcher’s performance, in-
cluding windcatchers’ position toward each other and partition’s posi-
tions in the most ecient conditions. Calautit et al. [119] investigated
the impact of position and distance of windcatchers on the velocity of
Fig. 10. Investigated models by Ghadiri et al. [115] .
Fig. 11. Investigated cases by Dehnavi et al. [116] .
Fig. 12. Investigated models by Zarandi [49] .
8
P.K. Sangdeh and N. Nasrollahi Energy and Built Environment xxx (xxxx) xxx
ARTICLE IN PRESS
JID: ENBENV [m5GeSdc; November 12, 2020;16:6 ]
Table 6
Topics of research about architectural solution and conclusion of them.
Topic Conclusion
Difference between the
performance of
windcatchers and
other openings
In areas with privilege wind, one-sided
windcatcher has higher efficiency,but in areas,
that direction of the wind is va riabl e other types
are better
Impact of height on
the performance of
windcatcher
Increasing the height of the windcatcher causes
improvement of the performance of it, but at
heights more than a particular height, rising in
the performance will not significantly increase
the height parameter.
Impact of distance and
height of surrender
buildings on the
performance of
windcatcher
Short buildings could enhance the performance of
windcatcher, but tall buildings cause all channels
of windcatchers
to act as a chimney.
Impact of wind
approach on the
performance of
windcatcher
Most ventilation rates occur at 0°. amount of it
decreases between o° and transition angle. At the
transition angle, ventilation arrives at zero.
Impact of velocity on
the efficiency of
windcatchers
In traditional windcatchers increasing in velocity
causes increasing in performance of windcatcher.
Impact of the shape of
inlets on the efficiency
of windcatcher
Divergent inlet has higher, and the
bulging-d ivergent inlet shape has the lowest
efficiency
Performance of
windcatchers with
various shapes of
blades
+ shape of internal blades is optimum for a
four-sided windcatcher.
Performance of
windcatchers with
different roofs.
Windcatcher with the curved roof has the highest
efficiency in 0 wind angle, but windcatcher with
the sloped roof has the lowest sensitivity against
changes in wind angle
entering airow and the performance of windcatchers. Results indicate
that oblique positions of windcatchers are more optimal than linear posi-
tion. The linear position could not supply minimum needed ventilation,
whereas incoming airow was more than required airow in an oblique
arrangement. Other research about the position of windcatchers done by
Attia and De Herde [95] . They studied dierent positions for Malqafs. A
1:20-scaled model was used in this research, and the assumed distance
between windcatchers was 60 centimeters. The only factor investigated
was the direction of the inlet. Results indicate that the best condition
was when one of them was windward, and the other was leeward. An-
other factor for enhancing the eciency of windcatchers is increasing
the number of interior blades. Hoseinnia et al. [67] changed the number
of blades, and other factors were xed for all cases. Then they investi-
gated the impact of blades on the velocity of incoming airow. For this
purpose, ve cases (with dierent blades) were considered (shown in
Fig. 13 ). Results indicated that the mean velocity of incoming airow
would increase with increasing the number of partitions (both wet and
Table 7
Topics of research about architectural solution and conclusion of them.
Author (year) Topic Solution
Calautit et al.
(2014)
Impact of various
arrangements of
windcatchers on the
performance of
windcatchers
Non-linear arrangement of
windcatcher causes
improvement in the
performance of each of them.
Attia et al.
(2009)
Different arrangements
of two malqafs
Being in opposite directions
causes one of them to bring
fresh air into indoor space and
another malqaf acts as a
chimney
Hosseinnia
et al. (2013)
Impact of the number of
blades on the efficiency
of windcatcher
Increasing the number of
openings causes improvement
in the efficiency.
Hosseinnia
et al. (2013)
Impact of wet partitions
on the performance of
windcatchers
Wet partitions cause more
decreasing in the temperature
of incoming air flow.
dry partitions). Moreover, moist partitions can add evaporative cooling
to windcatcher. Windcatcher with the evaporative cooling feature can
decrease indoor space temperature by 7.6° C and increase the relative
humidity of indoor space by 9.2 percent.
To put it briey, Table 7 contains architectural solutions for enhanc-
ing the function of windcatcher.
8. New designs for windcatcher
However, traditional windcatchers were benecial but had some dis-
advantages that are as follows [120] :
1- Dust and insects can enter in indoor spaces through windcatcher’s
shafts.
Sometimes, some part of airow which enters in interior spaces, exits
from another channel, and has no circulation in indoor areas.
The eciency of windcatchers in circumstances with a low velocity
of winds is low.
The modern windcatchers have to try to eliminate one or more of
these disadvantages. They are more likely to pay o when integrated
with new technologies and new designs [120] .
8.1. Windcatcher with rotating head
This kind of windcatcher has a rotating head that can be against the
wind’s direction at every angle it has. The material of it can cross light
to buildings proted by more daylights. Some of the main features of
this windcatcher is as follow:
- Using relative transparent material for crossing daylight.
- The upper part of it is circular and rotating.
- Number of it depends on temperature and needed ventilation rate
[121] .
Fig. 13. Investigated types of partitions by Hosein Nia et al. [67] .
9
P.K. Sangdeh and N. Nasrollahi Energy and Built Environment xxx (xxxx) xxx
ARTICLE IN PRESS
JID: ENBENV [m5GeSdc; November 12, 2020;16:6 ]
8.2. Windcatchers with a wetted column, wetted sur- face
Bahadori et al. [122] compared two new types of windcatchers with
traditional windcatchers: windcatchers with wet columns and wet sur-
faces. The results of this comparison show these two new types have
higher performance than traditional models [42] . In low velocities,
windcatchers with a wet surface and windcatchers with a wet col-
umn function more properly in other conditions. Noroozi and Veneris
[123] introduced a windcatcher, a combination of these two types. This
one-sided windcatcher has wet blades and wet pads on the inlet. The pad
can be closed or opened. This windcatcher was simulated in various pa-
rameters (velocities, opened, and closed pads). Results showed that this
windcatcher could decrease the cooling load signicantly. Soltani et al.
[124] investigated a windcatcher with a wetted surface. The proposed
windcatcher has a xed column and a rotating head. The inlet has a grid
pad wetted by a pump. Results showed that the wetted pad and rotating
head could improve the eciency of the windcatcher signicantly.
8.3. Down-draft evaporative cool tower
Passive down-draft evaporative cooling (PDEC) can be an active or
passive system [ 125