Fahadan Water Reservoir is an example of a subterranean reservoir system, which employs passive ventilation techniques alongside building strategies to control its internal environmental. The Fahadan Reservoir was built in 1115 g (equivalent to 1737ad), by Mohammad Amin, one of the leaders of the Fahadan neighborhood at that time. The location of the site is in the historic city of Yazd, Iran, which is subjected to arid climatic conditions and considerable seasonal changes.
The layout of the building is structured around a central water chamber with a singular access point coming off it. The chamber can be accessed from the adjacent bazaar by a staircase comprising 51 steps. This staircase has two roof light openings providing it with natural light and fresh air. It leads down from the bazaar at ground level to the foot of the faucet, which is located on the east side of the water chamber. The faucet is placed almost a meter above the base level of the chamber in order for the water to be extracted using the pressure created by its own weight while preventing the residue at the base level to enter into the faucet.
The water chamber of the reservoir is covered with a sharp dome, which acts in unison with four wind towers to regulate the temperature of the chamber. Fahadan has got four wind towers located at each corner of the chamber. Out of these symmetrically arranged wind towers, two are 4 sided and are built from brick while the other two are single-sided built from clay. The careful positioning of these two different types of wind towers facilitates the utilization of local wind patterns. The towers are designed to prevent dust and airborne pollutions from entering into the water reservoir, whilst enabling a constant flow of fresh air to circulate the space. Fresh air enters into the cistern through the four sided wind towers and exits through the single-sided ones.This circulatory system prevents the water from going stale and helps to keep the temperature inside the water chamber cool.
The water storage chamber is buried within the ground for structural reasons as well as to make use of the thermal mass capacity of the ground to maintain a stable water temperature cool. By digitally modeling the Fahadan Reservoir with the surrounding buildings and ground fabric accurate environmental analysis has been obtained. This analysis evaluates the thermal performance of the reservoir as well as the internal air pressures. The result of the thermal analysis from tests carried out on the 20th of July indicates that with a 300 temperature difference during the day and the peak temperature of 500 the ground temperature remains constant at around 300 C. The use of wind towers has enabled a reduction in water temperature by almost 11 0C from that of the ground, therefore highlighting the efficiency of the architectural system in place.
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