Wind tower is a key element in traditional architecture of Iran. It is
seen in settlements in hot, hot-dry and hot-humid climates. They look like
big chimneys in the sky line of ancient cities of Iran. They are vertical
shafts with vents on top to lead desired wind to the interior spaces and
provide thermal comfort. This architectural element shows the
compatibility of architectural design with natural environment. It
conserves energy and functions on the basis of sustainability principles.
A wind tower is an architectural device used for many centuries to create
natural ventilation in buildings.
The function of a wind tower tower is to catch cooler breeze that prevail
at a higher level above the ground and to direct it into the interior of
the buildings. It is not known who first invented the wind tower, although
some claim it originated in Iran and it can be seen in. wind towers come
in various designs, such as the uni-directional, bi-directional, and
A wind tower is a formal structural element in Iranian architecture that
is used to convey the wind current to the interior spaces of buildings in
order to provide living comfort for occupants. In Iranian architecture a
wind tower is a combi- nation of inlet and outlet openings. The tunnel
provides cool air for the building while serving as a conduit through
which the stuffiness within the building is conveyed through its shaft.
There were wind towers in Bam which were destroyed by earthquakes; they
weren't directly connected to the living hall. They were built away from
the house. An additional underground tunnel links the base of the wind
tower to the basement.
In most wind towers, especially the four sided types, the tower is divided
by partitions. One of the shafts operates all the time to receive the
breeze and the other three shafts work as outlet air passages. They convey
the stuffiness out of the living space through the “flue” (chimney)
effect. The chimney effect is based on the principle that the air density
increases with the increase in temperature. The difference in temperature
between the interior and exterior parts of a building and between
different regions creates different pressures and result in air cur-
rents. The average relative humidity in moisture in hot and dry regions is
low and it is necessary more humidity there for wind towers are used to
provide living comfort through the use of the air current and evaporation.
Through the wind tower, the air current first passes over a stone pond and
fountain after entering a building, thereby bringing humidity to the other
spaces in the building
First, a wind tower is capped and has several directional ports at
the top (traditionally four). By closing all but the one facing away
from the incoming wind, air is drawn upwards using the Coanda effect,
similar to how opening one facing the wind would push air down the
shaft. This generates significant cooling ventilation within the
structure below, but is not enough to bring the temperature below
ambient alone - it would simply draw hot air in through any cracks or
windows in the structure below.
Therefore, the key to generating frigid temperatures seems to be
that there are very few cracks at the base of the thick structure
below, but there is a significant air gap above the qanat (a water
management system used to provide a reliable supply of water to human
settlements or for irrigation in hot, arid and semi-arid climates). A
qanat has quite a lot of water inside, because there are frequent
well-like reservoirs along its path. Completely shaded from the sun, a
qanat also aggregates the cold, sinking air of the night, which is
then trapped within, unable to rise up to the less dense surface air.
A wind tower, however, can create a pressure gradient which sucks at
least a small amount of air upwards through a house. This cool, dry
night air, being pulled over a long passage of water, evaporates some
of it and is cooled down further.
Finally, in a windless environment or waterless house, a wind tower
functions as a Solar or thermal chimney that uses convection of air
heated by passive solar energy. It creates a pressure gradient which
allows less dense hot air to travel upwards and escape out the top.
This is also compounded significantly by the day-night cycle mentioned
above, trapping cool air below. The temperature in such an environment
can't drop below the nightly low temperature. These last two functions
have gained some ground in Western architecture, and there are several
commercial products using the name wind tower.
When coupled with thick mud brick, the wind tower is able to chill
lower-level spaces in mosques and houses in the middle of the day to
So effective has been the wind tower in Persian architecture that it has
also been routinely used as a refrigerating device.
Many traditional water reservoirs, or ab anbars, are built with wind
towers that are capable of storing water at near freezing temperatures for
months in summer. High humidity environments destroy the evaporative
cooling effect enjoyed in the dry conditions seen on the Iranian plateau;
hence the ubiquitous use of these devices in drier areas such as Yazd,
Kashan, Nain, and Bam.