Vernacular Passive Cooling Systems in Iran
A vernacular passive cooling system applies to any passive cooling system that has traditionally been employed and used in vernacular buildings. In contrast to modern air-conditioning technologies, vernacular means of cooling in hot and arid regions have largely been ‘passive’. Vernacular passive techniques and their long-standing features have slowly been perfected in traditional societies and are associated with and adapted to the climate.
A considerable number of commentators have identified various traditional vernacular cooling techniques and systems as used in traditional dwellings in hot climates globally, and particularly in the Middle East and Iran.
Norbert Lechner, a professor emeritus in the College of Architecture, Design, and Construction at Auburn University in the US, for example, has described a number of vernacular architectural cooling strategies in hot and dry climates, listing massive constructions, small openings, light-coloured exterior surfaces, closely clustered buildings and the use of roofs for sleeping at night.
Many academics have written about vernacular architectural passive cooling methods in the hot and dry climates of Iran.
Bruce Bonine pinpoints courtyards, thick adobe walls, ivans, underground rooms, wind-towers, domes, air vents and seasonal rooms as the main features of traditional passive cooling systems in Iran which have enabled residents to be quite comfortable:
In pre-industrial times, the traditional Iranian house represented a most comfortable and rational design for a hot arid climate. The open courtyard and such features as thick adobe walls, ivans, underground rooms, wind towers, domes, and air vents all indicate an intimate knowledge of the environment as well as a sophisticated indigenous building technology.
Seasonal usage of rooms, a focus on a courtyard pool and vegetation; and the extensive utilization of the roof are fantastically simple solutions to the extremes of a hot (and cold) arid climate.
Iranian-born author and professor, Masoud Kheirabadi, highlights the existence of compact urban form, winding streets and courtyards as main features of Iranian vernacular cooling systems:
To adjust to the hostile climate, traditional Iranian urban planners learned to minimize the direct impact of solar radiation, to soften the blow of harmful and unpleasant winds, and to optimize the use of shade, breeze, and water. The planners’ objectives were achieved by adopting a compact urban form, developing special street and alley patterns, and designing houses with courtyards.
According to Vahid Ghobadian, Iranian architecture professor, central courtyards, distinct summer and winter quarters, wind-catchers, heavy masonry walls and compact urban texture are major traditional passive cooling components: Traditionally, inwardly-oriented houses — with central courtyards — would protect the interior of the buildings from the frequent sandstorms.
These houses are called ‘four seasons’ houses because the north side of the house, which receives direct sunlight, is used as the family residence during the cold months of the year. The south side of the house, which is always in shade, is used during the summer months. Wind catchers are usually built on top of the summer section. These houses are built with heavy masonry walls and vaults, which act as thermal masses and therefore reduce temperature fluctuations between day and night. The urban texture of traditional cities in this area is compact. In this way, the whole city is protected against sand storms, and winter heat loss through outside walls is also minimized.
Similarly a number of other experts claim that the compact form of the city, the narrow, twisting and covered passageways, wind-catchers, the orientation of buildings to sun and wind, the arrangement of separate summer and winter spaces, using local materials and natural energies, the construction of underground living spaces, deep central courtyards with greenery and pools of water, thick earthen walls, and reusing materials are the main vernacular urban and architectural solutions in hot and dry regions of Iran.
The above is a lightly edited version of part of a chapter entitled, ‘Vernacular Passive Cooling Systems in Iran’, from a book entitled, ‘Thermal Comfort in Hot Dry Climates; Traditional Dwellings in Iran’, written by Ahmadreza Foruzanmehr, published by Routledge Research in Architecture.