Our interest in the Boroujerdi House lies with its inherent ability to modulate climatic conditions through the use of specific spatial organisations and passive ventilation systems. This research is useful for informing our current design strategies for buildings and spaces in similar climates.
Built in 1857, the Boroujerdi House was one architect Ostad Ali Maryam Kashani’s more significant projects. The location of the house is in the historic part of the city Kashan, Iran, which has an arid to semi-arid climate. The layout of the building has been strategically organised in response to the distinct seasonal variations and temperature fluctuations that occur throughout the day. Its highly efficient use of passive ventilation and intricate cooling and lighting systems make Boroujerdi a model of sustainable design.
In plan the layout of the building and its grounds are introverted, with the building fabric skirting around the perimeter of the site while the main body of structure is positioned at the southern end. A series of linked spaces occupy the main body of the building, however it is the eastern and western porticos that serve as the primary functional spaces for daily use, which are incidentally less ornate and decorative.
The southern part of the house functions in contrast to the northern part. The northern part of the building is almost entirely enclosed, with few only openings, the southern part on the other hand has large openings in it facade along with a series of openings in the roof as well.
The extended arced facade on the north-facing part of the southern building provides shading, preventing direct sunlight to enter into the internal spaces. This shading helps to reduce internal thermal gain. The orientations of the roof openings work in correlation with the internal geometric configuration to modulate the amount of direct sunlight entering the building, resulting in a diffused natural light source.
The central dome also plays a significant role in the cooling and ventilation of the internal spaces of the building. The domes geometry accelerates the velocity of the wind, which influences the external and internal affect it has on the building.
The centre of the site opens up to form a rectangular courtyard with a pool positioned within it, trees and planting fringe the edge of this pool. The use of the pool is to provide evaporative cooling whilst the planting helps to reduce the thermal gain from the sun on the surface of the buildings facades by providing shading. During the hotter parts of the day the heat causes the air to expand, creating a difference in air pressure. This change in pressure facilitates the circulation of air through the yard. The cooler, heavier layer of air absorbs damp from the pool and vegetation in the courtyard whilst small dust particles become heavier due to the damp, and consequently settle on the ground.
The manipulation and harnessing of wind flow and air pressures allows for highly sophisticated passive cooling techniques to be used to control the buildings temperature. As the wind direction flows from south to north the velocity of the wind speed is affected by the geometry of the dome. The wind speed increases as it passes around the dome and its direction subsequently changes as it enters the central courtyard space passing over the water of the pool, which in turn cools its temperature. The cooled air then flows back into the north-facing openings of the southern part of the building with increased speed and pressure.
The high domed ceiling within the southern part of the building creates a natural stack effect during the summer months when the outside temperatures are at their highest. The upper layer of air within the central dome space is heated by the sun through the roof openings, whilst the cool air enters via openings at the lower levels of the building. This forms a passive heat exchange by natural convection. The roof openings and wind catchers positioned around the central dome also allow for night purge ventilation to occur. The wind catchers are designed to have octagonal openings, enabling them to catch the wind from any direction.
The study and analysis of passive environmental modulating systems found in vernacular architecture provides valuable resources for developing contemporary solutions to complex climatic criteria and functions.
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