Windcatcher as a Persian Sustainable Solution for Passive Cooling
Payam Nejat1,2* and Fatemeh Jomehzadeh3
1Faculty of Civil Engineering, University Technology Malaysia (UTM), Malaysia
2Advanced Building and Environment Research (ABER) center, UK
3Department of Environmental Engineering, University Technology Malaysia (UTM), Malaysia
Submission: June 02, 2018;Published: July 19, 2018
*Corresponding Author: Payam Nejat, Faculty of civil engineering, University Technology Malaysia (UTM), Malaysia, Advanced Building and Environment Research (ABER) center, UK, Email: email@example.com
How to cite this article: Payam N, Fatemeh J. Windcatcher as a Persian Sustainable Solution for Passive Cooling. Civil Eng Res J. 2018; 6(1):
Currently, building energy consumptionhas become an international issue especially in developing countries. In hot arid climate,60% of total building energy consumptionin this areais associated with cooling systems. Wind as an important renewable energy can play a prominentrole to supply natural ventilation inside the building and windcatcher as a traditional technique can be implemented for this purpose. In this paper the different types of windcatchers, its performance and functionwas reviewed. It can be concluded in most area this technique can be successfully be employed and help to reduce fossil energy consumption and related CO2 emissions.
In most of countries, the per capita energy utilization has been significantly raised particularly in the developed countries. Recently, in developing countries energy consumption increased and has high level which is as a result of general growth in different segments like transportation, residential, commercial, and industrial developments.
Therefore, it is essential to think through new degrees and methods to energy preservation in both developed and developing countries for building sector. Conservation of energy is explained as practical method in energy consumption without influencing the standard of occupants living in house [1,2].
Huge electricity consumption (particularly for cooling) has made trouble during peak hours to response to demand for many countries.
This enormous capacity building, which is completely dependent on fossil fuels, will encounter many countries with environmental threats and destructive effects on climate, rare water resources, land and air .
However, sustainable approach, which is one of the ways that can contribute in reduction of energy and CO2 emissions, emphasizes on utilization of local resources and passive approaches instead of active which use fossil fuels .
Energy efficient buildings’ design is currently a noticeable subject on account of the energy costs growth, environmental influences and energy consumption, particularly for global warming.
In fact, in many countries, research studies on efficient building design are growing rapid and commercial and residential buildings must include enhancements on energy saving policies [4-6].
Natural ventilation is one of energy efficient methods which canbe addressed in sustainable design to decrease overall consumption in buildings. In this paper windcatcher (as one type of natural ventilation methods) will be reviewed briefly in types performance, function and analysis.
This type forms the simplest one of natural ventilation. Via appropriate arrangement of openings, the enough current of natural ventilation can be achieved inside the building to decrease needs of conventional cooling.
Joined with windows, vents also can be used in designed
position where windows are not needed. Since this technique is
economic option, various experimental and numerical studies
have been done.
Courtyard which can be seen in many regions has been an
impactful method to supply natural ventilation for thousands
of years for mankind across the world.Courtyards provide a
relatively enclosed area to channel and direct airflow to some
openings and cause convective natural ventilation inside and
nearby the buildings.
Different investigations generally admit that the winddriven
ventilation can be raised by application of courtyard and
atria but mostly efficient for low rise buildings. Nonetheless, the
passive nature of this method shows that its efficiency depends
basically on the existence of its driving forces.
One of the conventional systems for providing natural
ventilation inside the buildings without utilization of
conventional energy is windcatcher. Over three thousand years,
people in Middle East used the windcatchers for many buildings.
They are known by various names like Badgir, Malghaf, etc. in
different areas of this district.
Windcatcher is usually a tall construction which has height
between 3 and 33m placed on the building roof (Figure 1).
The windcatcher design traditionally depended on the social
condition and wealth of house landlords, architects’ personal
experience as well as, and differed in the height of tower, number
and position of openings, cross-section of the air channels, and
tower position with attention to the structure [7-12].
In terms of external shape, it is generally considered two
main categories for wind catcher including unidirectional and
multidirectional wind catcher. The former also called one-sided
wind catcher and the latter is classified under three sorts: two,
three and four-sided wind catcher which usually have square
plan, hexahedral and octahedral wind catcher.
Many countries of the Middle East enjoyed unidirectional
windcatcher for those houses settling in regions which have a
permanent prevailing wind. The performance of this system is
mostly dependent upon the wind direction.
In other words, if there is an unfavorablewind directions,
one-sided windcatcher will not well function. Hence, inlet
openings of windcatcher should be at as much as high level to
enjoy stack effect (buoyancy effect) like a solar chimney function
for that special condition. Figure 2 depicts the structure of onesided
windcatcher, the wind goes in from the single opening and
passes via the living space and leaves the exhaust vents, doors,
In regions with strong predominate wind, two-sided wind
catcher is generally utilized which have two vents and two
distinct underneath halves. Figure3 shows the bidirectional
wind catcher is separated into two channels in order to supplying
(suction) and extraction of air flow.
The incident angle is the principal advantage of this device
compared to one-sided windcatcher in which the unidirectional
tower opening exposed under the transition angle and the
airflow rate through it tends to zero [8-14].
Figure 4 illustrates the three-sided wind catcher which
often has larger windward side with more openings to capture
as much predominant wind as possible. When air flow enters
through the wind catcher, air velocity increases owing to curved
form of openings.
Based on previous studies, an abundance of four-sided
windcatcher is more than other types of this system in the Middle
East. In areas where there is no specific direction for wind, foursided
windcatcher can be seen; therefore, its design is mainly
dependent upon capturing the wind from all directions. Foursided
windcatchers with decorations belong to a famous family’s
house in the city of Yazd, Iran as shown in Figure 5 .
These types of windcatchers have been usually seen with
regular multifaceted plans and they were designed in the shape
of hexagon or octagon. Generally, they are higher than other
windcatchers, especially eight-sided windcatcher; therefore,
they will have more stability against wind pressure as well as
tower form causes passing air flow with lower pressure.
The utilization of six-sided windcatchers is limited in the
world, however some of them are found as water-reservoirs in
Iran. Figure 6 shows the tallest traditional windcatcher of the
world with octagonal plan and approximately 40 meters high,
which places in a famous garden (DolatAbaad) in the city of
Yazd, Iran .
Windcatcher’s performance is based on the natural
ventilation with implementing both stack effect and wind driven
ventilation. There are two principal functions of windcatcher:
the first is to related to opening which should bring in fresh air
inside the building and second related to exit of windcatcher
which should remove hot and polluted air of inside the building
(the suction functions) and thus works such as a sucked and
ventilation system [9-11].
The windcatcher function can be explained by the fact a
flow from positive pressure to negative pressure causes the
ventilation. According to this fact, in windcatcher, the opening
in the wind direction absorbs the air into the building inside and
the inside air with negative pressure depart from the exit of the
windcatcher (Figure 1).
Computational Fluid Dynamics (CFD) is widely used for
studying windcatcher performance. The CFD models consist of
RANS (Reynolds Averaged Navier-Stokes equation) modelling
and LES (Large Eddy Simulation). The conservation equation
of permanency, energy, momentum, and concentrations of
chemical-species can be solved by RANS modeling .
An overview of applications of ventilation indicated that CFD
is the most popular tool used to assess the ventilation systems
including windcatcher. CFD has become a reliable tool for the
analysis of flows, heat transfer for any kind of ventilation and
cooling systems. With results of CFD software the performance
and efficiency of windcatcher can be assessed and easily can
study temperature distributions, air velocity, humidity, CO2
concentration, thermal comfort etc .
To validate the results wind tunnel experiment is done. The
wind tunnel can extract the air velocity, pressure coefficient, and
air flow directions [14,15].
In recent years attention toward wind energy as a green
source for natural ventilation has been drawn. Natural ventilation has different types which windcatcher is one of the most effect
ones. With respect to hot arid climate conditions in most of the
country there is high potential to implement the windcatcher.
Windcatcher can reduce temperature and provide fresh air for
occupants as well as reduction in CO2 concentration inside the
building. Windcatcher has different types which everyone is
suitable for a specific condition. This old traditional technique
can be merged with new building designs to raise the green
concept in the building sector.