passive building design for hot-arid climate in traditional iranian architecture

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Moossavi, Seyed Morteza. (2014). Passive Building Design for Hot-Arid Climate in Traditional

Iranian Architecture. GREENARCS – Green Architecture and Arts Online Journal (English), Page

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Passive Building Design for Hot-Arid Climate in

Traditional Iranian Architecture

Seyed Morteza Moossavi

Ph.D. Scholar of Architecture, M.D. Arch.

Architecture and Ekistics Department

Jamia Millia Islamia, New Delhi

_________________________________________________________________

Keawords: Passive Building Design, Passive Architecture, Traditional Iranian Architecture

Abstract

Nowadays, we are feeling so much pressing to change building design to use

natural systems, because of global warming, energy problems, and air pollution.

Before industrial age, we had a good knowledge about using of renewable

energies in architectural design, but we forgot them for a long time. Now we have

to go back to our last experience, especially passive solar architecture and

passive cooling, heating, ventilation.

There are so many natural cooling criteria and techniques in traditional Iranian

architecture such as:

Internal courtyard houses, The below-ground courtyard, Showdan, Shabestan,

Khishkhan, Hozkhaneh, Badgir (Windcatchers), Qanats

Also, design of building forms in hot-arid climate of Iran is harmonized with

climate. We can see some systems such as:

Arched roofs, Ice stores to preserve ice, adapted urban texture with desert life

conditions



In fact we can get complete resources about passive building design criteria and

techniques from more than seven thousand years background knowledge in

Iranian architecture that it is shown clearly in Islamic age.

The aim of this paper is to collect and present some passive cooling design

systems from Islamic Iranian architecture in hot-arid climate.

Introduction

The traditional architecture of Iran is the product of land, the local climate, and

people’s culture. The human needs and the environment represented the most

essential factors to be considered in their designs. The traditional and vernacular

architecture of this region introduced many realistic solutions and devices to the

local environmental problems in macro and micro scale which became a common

architectural feature in buildings.

Beyond the evident typology in Islamic Iranian architecture and the guiding

architectural principles, their buildings were shaped by a conceptual framework,

which developed an understanding of conscious responses to environmental,

urban and societal conditions of existence. Traditional buildings are the true

expression of the architecture that provides comfortable living conditions in all

different climates. In hot arid regions, in specific, the forms of these traditional

buildings have been shaped according to the available natural sources of energy,

which help reduce humidity and create natural ventilation. There are number of

architectural techniques and elements which help provide cooling in internal

spaces, including an inner courtyard, shabestan, local materials and wind-

catchers, khishkhan and so many other systems. This paper will try to show some

of these Iranian architects experiences.

Climate of Iran

Iran has a hot, dry climate characterized by long, hot, dry summers and short, cool

winters. January is the coldest month, with temperatures from 5°C to 10°C, and

August is the hottest month at 20°C to 30°C or more.

In most of the areas, summers are warm to hot with virtually continuous sunshine,

but high humidity on the southern coastal areas of the Persian Gulf. Daily



Temperatures can be very hot; on some days temperatures can reach easily 40°C

or more, especially along the Persian Gulf and Oman Sea which causes a danger

of heat exhaustion.

About 70 percent of the average rainfall in the country falls between November

and March; June through August are often rainless. Rainfall varies from season to

season and from year to year. Precipitation is sometimes concentrated in local,

but violent storms, causing erosion and local flooding, especially in the winter

months.

Caspian Mild and Wet

Caspian Mild

Mediterranean with Spring Rains

Mediterranean

Cold Mountains

Very Cold Mountains

Cold Semi-Desert

Hot Semi-Desert

Dry Desert

Hot Dry Desert

Hot Coastal Dry

Coastal Dry

Figure 1 Climate Map of Iran

A small area along the Caspian coast has a very different climate; here rainfall is

heaviest from late summer to midwinter but falls in general throughout the year.1

Hot-Arid Climate of Iran

Hard and cold winters, warm and dry summers, very low rate of rain, air humidity,

herbal cover, so much difference between day and night temperature and in salt

1 Weatheronline Website



desert and salt-desert border regions, the dusty winds are the outstanding climatic

specifications in this region.2

Passive Cooling Systems in Islamic Iranian Architecture

According to scale of cooling architectural systems in Iranian architecture from

urban scale to architectural elements, we give a classification in four parts:

- Morphology and urban texture

- Building form

- Architectural Spaces and Elements

- Materials

Morphology and Urban Texture

In movement through urban space to building spaces we can start from urban

texture parameters and systems that those were making cool space in Iranian

cities.

Urban Direction

Architects in the past with regard to weather, sunlight and wind (wind, air, storms,

dust, etc.) have designed some special direction for Iranian cities.

Iranian architects have used hexagonal shape to do that. They had totally three

directions and they have called them:

Order orientation (Roune rasteh in Persian language): North East - South West.

Isfahanian orientation (Roune Isfahani in Persian language): North West – South

East

Kermanian orientation (Roune Kermani in Persian language): West – East

2 Ahmadkhani Maleki, 2011



Figure 2 From Left to Right: Order Orientation, Isfahanian Orientation, and Kermanian

Orientation

Dense Texture

As we can see in maps of Yazd and Kashan cities, there are connected buildings

and covered bazaars in these cities. So that in a total overview you can see it as a

single roof with holes (courtyards), and some alleys cut in this roof.

Figure 3 Dense Texture of Kashan, Iran

Surrounded Urban Spaces

All the public and private spaces are surrounded with tall walls and they have

internal courtyards to decrease the effect of hot and sandy winds.



Figure 4 Ganj-Alikhan Square, Kerman, Iran

Covered Bazaar

To provide shade and protect from hot sun and dusty winds, Bazaars; as main

lanes in Iranian cities are covered by tall roofs with air vent elements.

Figure 5 Bazar-e Vakil, Shiraz, Iran

Narrow Irregular Passages

The alleys are not straight. Those are narrow to provide shade in most times a

day and be comfort.



All passages have tall walls and roofs in some parts to make shade and protect

people of sunlight and sandy winds too.

Figure 6 A Narrow Alley in Yazd, Iran

Sabat

A sabat is designed in order keep safe human living in desert from direct radiation

of sunlight in shade for some moments. In fact, Iranian architects, in the same

instances, built houses up to somewhere lying on the lane and began to build one

or more protruded rooms with same eaves above the passage all commuting was

made under these rooms called sabats. A sabat can modulate a transient

temperature. It is such a way to his pedestrian on his destination is positioned in

shade in a suitable succession.



Also we can say that sabats are climate comfort entrance spaces for houses.

Figure 7 A Sabat in an Alley, Yazd, Iran

Building Form

Second scale through urban texture to building spaces will be building form that

we should focus on that.

Inverted Architecture

Iranian architects has designed an internal or inverted architecture, separate of

alleys and public urban spaces, to achieve minimum absorption of solar energy by

outdoor walls all the buildings about each other.



Domed Roofs

In the past, there were several ways of reducing the heat inside the buildings with

the benefit of radiant cooling. Domed roofs have been widely used in traditional

architecture mainly in hot and dry climates and have had an extreme effect on the

reducing the building's loads. The form of domes presents two different benefits.

During the day, always some area of the dome is in shadow while at night full

hemisphere sees the night sky. Thus, radiant heating is minimized while radiant

cooling is maximized.

Figure 8 Radiant Heating: Minimized and Radiant Cooling:Maximized

Domed Roofs in Passive Iranian Architecture

Courtyard

The courtyard in a hot dry climate is usually the heart of the dwelling spatially,

socially, and environmentally. Although, the size of the land, to some extent, is

influential, the average sizes of the courtyards are generally determined according

to the latitude. They are narrow enough to maintain a shaded area during the heat

of the day in summer, but wide enough to receive solar radiation in winter. A

courtyard can provide security, privacy, and a comfortable place within the house.

The courtyard where it is usually planted with trees, flowers and other plants, not

only provides comfortable condition and beautiful setting, but also supplies some

shade and increase the relative humidity of the courtyard space. In order to

reduce the area affected by the solar radiation, compact forms are chosen. Shady

areas can be obtained by arranging those forms of courtyards with the help of



plants and water for evaporative cooling. The floor temperature can be reduced by

the high walls surrounding the courtyard, and the open areas can be used during

the day. Water channels poured out from the pool are important elements for

cooling.

Figure 9 Ameri’s House Courtyard, Kashan, Iran

Courtyards are always in the ground floor and have distinct forms depending on

the landscape of the house. Even without modern, mechanical heating or cooling

systems, the courtyard house provides a comfortable living environment through

seasonal usage of sections of the structure.

Godalbaghcheh (Padiav)

The depth of the yards was more than the normal to have access to Qanat water

or subterranean canal of water, which was passing underground of yard, to water

garden and below ground courtyard. These yards were called Godalbaghcheh or

Padiav. By having a full of plants and trees and naturally because of evaporation

and sudation they are acting as a cool and fresh air generator for the upper yard



spaces. The floor of the yard was paved with square bricks called paved bricks,

which water and broom were used to clean them and it caused the yard space to

become cool.

Figure 10 A Godalbaghcheh in a Courtyard, Kashan, Iran

Inner Spaces and Elements

Third scale in our discuss on cooling systems of traditional Iranian architecture is

inner spaces and elements.



Winter Portion and Summer Portion

Those houses are known as four season houses from the structure to the

decorations are designed to meet the climate of this region. The two north and

south fronts, as the most suitable directions for buildings are allocated for summer

and winter dwelling. The northern front or "Panah" that opens to the winter sun is

the sitting room of family. In another front "Nesar" backs sunshine and essentially,

it is a veranda with tall roof and wind catcher as the sitting place of family and

most often, the "basement" is built below it. In hot seasons, the temperature of

cellar-being underground is less than other parts.

Figure 11 Winter Portion and Summer Portion in Iranian Architecture

The Winter Portion

In this part a big room with a large window (Orosi in Persian language) toward the

sun catches the rays of sun, and gets warm very fast in the morning. It gets warm

with direct sun. The floor, the walls and the roof are made with mud-brick. They

work as good heat storage, so they gain a large amount of heat and they give it

back with 7-9 hours delay (time-lag) during night. So the nights are not too cold.



The walls that got cold during the night are not effective because direct sun warms

the room up during the day.

The Summer Portion

This part works in the summer, gaining the least sunshine, with a wind catcher

and Kolah Farangi (a space with dome roof and vents on the dome) also a Talar.

The summer portion (Talar, wind catcher and Kolah Farangi) and the summer

room in the corner without any heat gain make a cool weather in hot season.

Figure 12 Shading and Ventilation in Summer Portion vs Winter Portion

Aivan and Ravaq

Eyvan and Ravaq, semi-open areas, are used to create shady and cool living

spaces during the day. The Aivan, three side a closed passageway in front of the

"rooms", permits a common life inside (an open living room inside the house).

Usually they are oriented to the south. Especially, south and east oriented Ayvans

are very cool and provide shady places during summer afternoons. The Ravaq

semi-open colonnade arranged in the courtyard always provides shady areas.



Figure 13 Ravaq, Semi-Open and Shaded Colonade

Wind-catcher

Wind-catchers have been used in Iran for centuries, and regarding the region

they have been differently designed based on the elevation and direction of the

wind. Wind-catchers mainly work based on the fact that the wall against the wind

is cooled off and the natural ventilation is done by the pressure differences inside

and outside the building, high air pressure then is sucked in, and low air pressure

and warm air comes out.

Wind-catchers, in Iran, are designed to cool off the building based on earlier,

convection, evaporation or both.

Figure 14 Simplified Figure of Wind-Catcher (Badgir) Function



Air-vent of Dom Roof

The operation of an air-vent depends on the fact that when air flows over a

cylindrical or spherical object, the velocity at the apex decreases. If there is a hole

at the apex of a domed or cylindrical roof, the different in pressure includes the hot

air under the roof to flow out through the vent.

An air-vent is usually protected by small cap in which there are openings that

direct the wind across the vent. Since the functioning of the vent depends on air

flowing over a curved surface, roofs with vents are oriented to present the

maximum curve to the wind. In areas where the wind is a prevailing one cylindrical

roof are built with the axis of the cylinder perpendicular to the wind direction, in

areas where the winds blow in all directions domed roofs are employed. Air-vents

are usually placed over the living rooms of buildings.

Figure 15 Shematic Figure of Air-vent Function

Shabestan

A Shabestan or Shabistan is an underground space that can be usually found in

traditional architecture of mosques, houses, and schools in ancient Persia (Iran).

These spaces were usually used during summers and could be ventilated by

wind-catchers and qanats.



Figure 16 Shabestan as a Cooling System in Hotest Days

Windows

Generally in hot and dry regions windows are small and are located in the upper

parts of walls just near the ceiling. Although external walls do not have so many

windows there are so many of them on the yard facing internal walls. Passing

ventilation is done by these windows. Wind-catcher also helps to the internal

ventilation.

Ray Wall (Tabeshband)

In the façade, the ray wall with almost thin sunshine cut blades with 6 to 15

centimeters thickness are used, around which, windows and holes would be

worked for shadows. Those who worked on top of threshold or window were

called horizontal wall or shadow top. In addition, on top of threshold, the bar walls,

in form of two small shelves with two oblique coat were made. Ray walls and bar

walls were able to prevent serve sunshine.

http://en.wikipedia.org/wiki/File:Qanat_wind_tower.svg



Figure 17 Raywall (Tabeshband) to Protect against Sun Radiation

Materials

Every building material in a desert town is composed of mud and its derivatives. In

fact, nothing but mud and mortar can be used in such regions because there are

no other building materials in the region.

Due to very hot temperatures, the building materials absorb heat from the sun and

make it available later when the sun goes down. In other words, this energy is

retained in the walls about 8 hours and the other parts of the building envelope



and is gradually transferred to the inner compartments. Such a quickly provides

leads to two alternatives in cold and warm season.

Use of vernacular materials such as brick and adobe is always one of the

concerns in the architecture of buildings, in hot-arid climate of Iran.

Figure 18 Self-Efficient Materials, Optical and Thermo-Physical Properties of the Building

Envelope

In the hot and dry climatic areas in Iran, in examples of traditional architecture, to

benefit from the time lag of temperatures in the building envelope, materials with

greater thermal mass have been chosen.



These kinds of thermally massed envelope details are very convenient for

continental climates, where the summers are very severe with high swings in daily

temperature variations.

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