Nazanin Salimi
(Photo: Masoud)



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Research
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Effects of climate on the form & elevation of buildings in Iran
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Architecture
 
By: Nazanin Salimi, Iran

Introduction
When human being chose “Iran” as his dwelling place since many generations before, he began constructing it. Then he encountered with various climates, therefore he tried to struggle with environmental conditions, and create suitable internal spaces, and initiated different constructing methods to adapt to the environment. 

because of different climates in Iran, there are different building systems. There are also valuable experiences in the field of designing, building and choosing of materials for traditional buildings, aimed at struggling with environment conditions.

Using local material, with respect to their stability and resistance toward heavy load and pressures, heat, cold and also rain and snowfalls are the factors that affect the appearances of traditional architecture in Iran.

In Iranian traditional architecture, the buildings are constructed according to the geographical location. And according to the position of the ceiling, there are some needs for decreasing the space, which is under the direct radiation of sunlight, choosing appropriate materials, constructing shades in each areas, walls, ventilation-shaft, basements, central yards, shelters with expanded shadows, windows facing sun, constructing reservoir etc. These factors make buildings struggle with such external matters in such a way that the best internal space will be created without using the complex set of energy and pollutant systems.
In another word, the past generations have known about the rules and using sun systems and have applied it all.

Division of climate in Iran
Iran has been located in geographical latitude of 40º, 25' North degree, this country is one of the hot countries in the world. This area is a height plateau; and there are few percent of the areas with the height lower than 475 m and lower than the sea level.
The characteristics of each climate in Iran

1) Humid & mild climate (Caspian beach)
Caspian beach with temperate weather and a lot of rainfall is considering as a temperate zone. This area is like a band between Caspian Sea and mountain chains of Alborz, with low plains, the more it goes towards the east, the more the more the humidity and the temperate decreases. In fact, Alborz Mountains separates Caspian from the central plateau and creates two different weather conditions. The characteristic of this climate is the high humidity of the weather and temperate weather.
The temperature in summer is between 25º and 30º centigrade, 20º to 23º centigrade at night, and above 0º centigrade in winter, rainfall is very common in the zone and in summer as a rainstorm. Rasht, Anzali, Ramssar, Babolsar and Gorgan are located in this area.
2) Cold climate (west mountains)
West Mountains consist of west slopes of the central Mountain chains in Iran. In this area the average temperature in the hottest month of the year is more than 10 degree and the less temperature in the coldest month is -3º centigrade and it is considered as a cold region. West mountain chains, like a barrier, prevent the penetration of Mediterranean humid weather into the Iran Plateau and maintain the humidity in its slopes. One of the characters of this climate is the intense hot in the valleys in summer and it’s mild in winter. The amount and intensity of the sunlight is high in summer and very low in winter. Winter is long, hard and cold and several months of the year, the ice covers the area. In all over of this area, from Azerbaijan to Fars, winter is very hard and the coldness begins from the beginning of November and continues more and less until the end of March. The amount of the rainfall is low in summer and high in winter in the shape of snowfall. Snow covers the mountains in the heights more than 3000 meters. In general, in this zone, the short spring separates winter from summer. Tabriz, Oroumieh, Sanandaj and Hamadan are located in this zone.
3) Warm & dry climate (central plateau)
In this climate which consists of the most area of semi equatorial areas, the weather is dry because of the migrate wind from south west & north west to the equator. These winds loose the most humidity while passing through the big continent. In addition, in semi equatorial zones with high air pressure, weather is hot and dry because of moving the higher layer to the down of atmosphere. Because of the dryness of the weather in this zone that is following with another characters, designing constructions is completely based on the weather condition. The sunlight is intense and the sky is without cloud in the most times of the year. But because of the movement of layers near the earth, mist, storm and also dust will appear in the afternoons. The reduction of humidity and also cloud in the sky has caused a big range of air temperature as follows; In summer, the sun light warms up the earth up to 70º centigrade during the day, whereas during the night, the temperature of the earth level decreases quickly and reaches to 15º centigrade and lower.
In central plateau that is the greatest area of Iran and surrounded with high lands, the weather is dry and warm. It has hard and cold winter and warm and dry summers.
Due to the scattered geographical situation in central plateau we can recognize two distinguished semi-desert and desert weather.
3-1 Semi-desert area
The existence of slopes of the mountains of north, west, south, central mountains, and east scattered plateaus has created independent zones due to the central plateaus because of the elevations and the damp of humid wind passes by these elevations. A mild climate in proportion to the central plateau is created and whenever we go from west to east, humid wind decreases while the dry weather increases.
3-2 desert area
Central low plateaus of the east and south east of Iran have desert dry weather. One of the characters of such weather is the high difference of the temperature at night and daytime during the summer. The lowest level of a relative humidity in Iran exists in Dasht Lout area, which is undoubtedly the warmest zone in Iran. Tehran, Meshed, Isfahan and Shiraz are semi-desert cities and Zahedan and Yazd are desert cities too.
4)- Humid and warm climate (south beaches)
The south beach of Iran, which has been separated by Zagros mountain chains from the central plateau, has the humid and warm climate. One of the characters of this climate is that the weather is very warm during summer and mild during winter. Maximum temperature in this area in summer is 35º to 40º centigrade and the maximum relative humidity reaches to 10%. The humidity in this climate is high during all season of the year. Therefore the difference of the temperature during night and day time in different seasons is low. The difference of the temperature in beach and sea in these areas has created sea and earth breeze; but this limits to a narrow beach band and the weather is calm in local areas and the speed of the wind is very low. Another characteristics of this climate are the high sun radiation that causes damages to the eyes.
Bandar Abbas, Jask, Abadan and Ahwaz are cities with this climate that are differentiated from each other according to their location in different beaches, their distance to the sea, air humidity and temperature and level of rainfall. In general the level of raining fall in Persian Gulf is higher and more regular, while the Beach of Oman Sea, affected by Indian Ocean winds, has irregular rainfall during the year.

Climate divisions and architectural typology

According to the native architectural forms and structures in different areas of Iran, it seems that that the variable characteristics of different climates in Iran have affected on creation of the cities and also the architectural formation of these areas. Therefore, the exact distinction of climate districts in the country, and also acquiring the climate characteristics in different areas has very important role in suitable designing. We study native architecture characteristics according to the four climate areas of Iran due to the relationship between climate and architecture of each area and also the difference of climates that has created the changes, native architecture of different areas and finally determination of architecture typology of Iran. 

A) Native architecture characteristics in the areas with mild and humid climate
1) Natural effective parameters on building
1-1) Sun
Due to the high rainfall in these areas, the roofs are made with high slope. The slope level with west-east direction gets lighter in summer in comparison with winter.
Surfaces with the slope toward south get more sun radiation in winter. In autumn and spring, the south slope surfaces get 20% or more than the east and west slope surfaces. Surfaces with the slope towards north receive the less sun radiation during the year.
2-1) Wind 
The way of blowing of the wind in an area is an important parameter for determining the building’s direction.
In north humid areas of Caspian Sea beaches, sea and earth breezes are blowing. Their direction during the day is from the sea towards the beach and during the night, it is from the beach to the sea while the direction and the severe of the movement of these breezes are effected by pressure differences. In summer when the 
Pressure in northern beaches of Iran is more than the pressure in central plateau , the air moves from the area with high pressure i.e. from sea towards beaches; for this reason Mangil area has hard northern winds during the whole summer.
Natural ventilation, with no except, is used in all the buildings of this area. In general, all the buildings have expanded and open plans and all of them have long and narrow geometric plans. For the main use of the wind blowing to create natural ventilation, rooms are located in the buildings due to the blowing of the wind. In the areas with high blow of the wind, all parts of the building towards the wind are completely closed. Because of using the best of wind blowing and because of great water sources and availability of water, the buildings are located non-concentrated and with big distances.
3-1-Humidity and rain fall
3-1-1 Rain fall
Because of high rainfall in these areas, the roofs are made with slope and mostly with high slopes effecting the form of the buildings to keep the rooms safe from the rain, the extended - balconies are made around the rooms. These spaces are used for working, resting and sometimes for storing agricultural products during the most times of the year.
3-2-1 Humidity
In high humidity beaches and the borders near the sea, the buildings are made on the wooden pedestals to prevent the penetration of humidity inside the building but on the slopes of the mountains, with less humidity, houses are built on the stone, soil...
Different ways of the penetration of the humidity into the buildings
Humidity in the building is maybe as a result of some parameters as the penetration of rain into the wall and the roof, or into the internal surfaces from the seams of the windows, and great humidity because of the internal systems producing the humidity and penetration of water from walls and roof.
Choosing the material of the walls to prevent the penetration of humidity into the internal spaces
Materials such as brick, and usual concrete or light concrete and cement block are penetrable against water and steam and when these materials are exposed to rain, distills will appear in them.
To prevent the penetration, it’s necessary to cover the outside surface of such walls with special and good quality layers. It applies to the cement block too. Empty walls with masonry materials consist of an external layer and an internal layer and surround a space between itself, if there is no connection between these two layers, The internal air of the wall cuts the stream of humidity, therefore it prevents the direct penetration and frequent penetration of rain from the external layer of wall to the internal layer.
Filling the empty spaces between two layers with the materials strong against the heat, which are water resistant, increases thermal strength of the wall and doesn't have a negative effect on the wall-strength against rainfalls.
If the conductor layers are installed inside the wall to increase the thermal strength of the wall, all layers must be uniform and with no steam to prevent the humidity penetration inside the wall.
The best and useful wall that can meet all the problems of preventing the humidity inside the buildings is a two-layer wall consists of heavy, thick and internal layer, which is penetratable having thermal strength and an external non-penetratable cover. In the empty space between this two-layers, it must be possible to create ventilation and also evacuation of the water result from humidity. Therefore this high humidity only appears in the internal surface of external layer and doesn't hurt the main wall, or in other words the internal layers.

Effects of climate on elevation of the building facade in mild and humid areas

Direction of the building must be in the way of wind blowing, it is – because of the importance of creating draught in mild and humid areas to use the most of wind stream in creating draught.
In these areas, the windows with big sizes are not so important, it is because by having small windows, (if located in a good place), we can use the most of sun energy and the wind(to create draught). But in places where it is not possible to create draught, large windows are useful to cool the air inside of the houses especial in the evening.
Choosing building’s materials suitable for mild and humid climate
In mild and humid areas, the west elevation of building must be constructed with the heavy-materials with high thermal capacity to prevent the heat resulting from san radiation into the house in the evening, whereas the other part must be constructed with materials with high thermal strength.
Effects of the climate on building forms in mild and damp climate
Although the temperature of mild areas is in a limit that makes it possible for the building plan to be flexible, the expansion of the plan along the east and west axle is necessary in these areas.
In this climate, the intensity of the sun light on the walls in different elevations, even west and east walls is less than the other areas. As a result, in these areas, we can use natural forms. But the forms of the building have to be definitely expanded along with the east and west axle. Extending the building form along the east-west axle, creates the draught inside the buildings and also decreases the internal humidity.
If the building is located in the complete shade, its plan can be completely open and free.
Characteristic of native architecture in the cold and mountainous area
Although the cold and it’s durability is different in cold areas, but generally the principles that have been executed to prevent of wasting of the heat in the building are alike and similar to the principles that are being noticed in architecture of dry and hot areas. In cold areas, the source of the heat is located inside the building and it has been tried to warm up the building by natural sources, large stoves or the heat resulting from human bodies, cooking or pets.

Natural factors effective on the building designs in mountainous and cold climate

1-1) Sunshine
The form and the way of locating the building for the maximum use of the sun
In cold climate, the external layer of building must be insulated completely against transmission of thermal conducts. Therefore, it's not good to absorb sun energy by opaque surfaces of the buildings .
The better solution is to use windows, sun light absorbents and also the form, location & the survey of the building and location of installed windows are important too. Considering the line of the sun movement in winter is very short and lower than the line of its movement during summer, less sun energy will be absorbed in winter. The best solution for using the sun energy during winter is allocating wall and main windows of building in the south part. In most cases rotating the building through east south (about 15º) is better, and in order to make it use the most of the sun light before noon than the sun light in the afternoon, and the absorption of the heat by the construction begins earlier. For using the most of sunshine in cold mountainous areas, we must decrease allocating opener to minimums in the north, west, and east directions.
North, west and east elevations are not in a good condition with a view to the blowing of the winter winds and for not being exposed to the sun light during winter. Therefore, south elevation of building is the best place for installing building openers.
When it's necessary to install windows on North, west and east walls, they would rather be smaller, and some places have to be considered for them with the most usages.
Effect of sun light on the roof structures
In these areas the roofs are flat, and horizontal surfaces and flat roofs during summer absorb the most of direct sun light and the least during winter. It is even less than the amount of sunlight that the southeast and west-south walls absorb in this season.
The reason for choosing for the flat roof in these areas is to keep the snow on the roof as the heat isolator.
2-1) Wind
The movement of the mass of the air, resulting from the air pressure differences, cannot be changed. But the speed and Direction of wind movement that is blowing near the earth surface is controllable. As the blowing of the wind in cold mountainous areas results from the Height Mountains in these areas, it is prevented by different ways in these kinds of constructions.
Form and location of buildings to decrease the wind turbulence
Winter wind affects decreasing buildings' heat by increasing the penetration of outside air and also increasing heat conduction from external surface of the building.
In a building with a suitable insulation, the effect of penetration of outside air in wasting energy is more than the effectiveness of heat transmission. Therefore the best solution is to decrease the possible differences between two buildings and to decrease air speed to be less in touch with external surface of building. 
This method is based on using breeze stream in summer. The less important must be located where winter wind blows. Doors, windows, and openers that are vulnerable against penetration of air streams must be located in a place with the least air pressure. It’s cleared that before designing the building, the direction that the winter winds blow from must be considered. By designing precincts and a correct location of the building, we can decrease the surfaces exposed to the wind. In the areas where the direction of winter wind blowing is constantly changing, the best solution is decreasing the roof slope and the whole height of the building. This matter has led to the decrease the building strength against the wind and relatively makes the air pass monstrously.
In the areas where the wind is blowing from a predictable direction, the strength of the building structure against the wind can be decreased due to the way of allocating the building on the earth. A suitable geometric form with low strength against the current of the air is possibly a form like a short dome. For the common buildings, taking little attention and applying more skills about the height, slope of the roof, direction of building location or the construction body touch the earth surface we can decrease the surfaces, exposed to the wind to the lowest limit.
Compactness of the form in the plan is the first rule for decreasing the touch with the wind current and the direction of the location is important as much.
The round corners of the building decrease the rising air pressure by conducting the air current around the construction.
Therefore, the surface of flat and uniform walls shows the lowest strength against air current and as a result, the level of air pressure will remain at the least. Angling the building with the imagination that the sharp edge of each corner causes the slipping of the load has an opposite result. Increasing the width surface is resulting from angling the building against wind stream. And effect of the wind will be more in such a way that the amount of tension forces and air pressure in the building will be more than they were.
Breaker wind
For preventing winter winds into the building in cold areas, we must use breaker wind. A breaker wind will divert the air stream to the above and create a calm and supported area. The largest part of this supported area is next to the breaker and back of the wind.
In this place, the further away from the back part of the breaker wind, the more it will be placed against the wind until it receives the primary speed of the wind. In the part that is in the stream of the wind, there is a breaker wind especially the same one that is completely compressed and a small calm area.
If the breaker has pores, such as the trees raw, the above part, which is in the stream of the load will be maintained against the wind. In the back part, such a breaker is a supported area against the wind and will be smaller than the breaker and will be placed far from distance.
The kind of the breaker will affect the direction and the form of air stream and also the area of the supported place. Creating the turning of the air stream in the above part of the breaker will cause decreasing of function of such a breaker.
The general principles of breaker designing
The vastness of the area supported against wind, is suit with the height of breaker. The higher the barrier, the more is the length of the supported area. Additionally, the angle of the breeder proportion to the wind direction is important. The more vertical breaker would have the most effect.
Effects of climate on the building facade in cold mountainous areas
In cold mountainous areas, windows are bigger than dry and hot area to make the best use of sun energy. As the case was in humid and mild areas, in these areas, a terrace is constructed in front of the windows to prevent entering of the rainfalls in to the house. 
Since dark colors absorb radiation more than light colors, therefore materials of the building façade are mainly dark in this area. 
Choosing building material according to cold mountainous climate
In order to keep the internal weather condition fixed in cold areas, the resistance of materials against heat must increase. Additionally the west walls and also internal part of the building must be constructed with some heavy materials.
In the areas with severe coldness, heavy walls are necessary to balance the heat. It is also necessary to use heat insulator to prevent heat transmission.
Generally speaking two main factors are considered while determining building materials: one is the critical outside conditions and the other is the best temperature. First the most critical weather condition would be recognized and then the best temperature would be determined. At the last stage the most appropriate building materials will be chosen accordingly. 
Effects of climate on the building formats in cold mountainous climate
The format of the building has an important effect on so many factors such as adjusting the building condition and climate as well as moderating the transmission of the critical outside weather conditions to the buildings. Therefore open format buildings or the formats in which the south-north frontage is lengthier than the west-east frontage are not suitable. And it is better for the building to be more compressed in mountainous cold climate and their plan should be in foursquare shape. That way they can resist the cold. The cubical two story buildings are the best kind for controlling the internal heat in the building during winter.
Direction of building construction in mountainous cold climates
Since getting the most sunlight is necessary in cold mountainous climate, therefore buildings must locate toward a direction so that they can receive the highest sun radiation. Thus the main facade of building must be placed toward the south in order to create the best heat condition inside the building. So the northern façade of buildings decreases to the minimum surface.

The specifications of local architecture in tropical areas

The principles applying to the architecture of tropical areas are so much similar to that of raw area. 
1) The natural forces affecting on building design in tropical areas
1-1 Sunlight
Due to high sun energy in this area, the most attempts are made to locate the buildings in the shadows. In this area, wide and roofed verandas are used to prevent rain and provide a shadow on room walls, too. 
1-2 The wind
Natural air conditioning is not that much important because of the warmth and humidity of the weather in the region. Therefore enough forecasts are not made to make drafty rooms. 
Some big vents are installed in this climate in order to use chilly see breeze. Most of the buildings of the area enjoy vents. Nonetheless in the further areas that are less influenced by sea breeze, the vents are small and short, and there are no vents in many other areas. 
2) The effects of climate on buildings in tropical area
Skin wetness is one of the most important problems in the clement areas, which is due to the high humidity of the weather. Therefore the summary of the principles that should be applied in humid and clement climates are as follows:
· Installing influential and permanent air conditioning
· Protecting walls and windows against sunlight and rain penetration
· Preventing inside weather from warming in day
· Decreasing the warmth to the minimum amount at night
Big windows are very useful provided that they are protected against sunlight, rain penetration and insect entry. It is because such openers not only increase natural conditioning but also lead to the decrease of internal temperature at night and in the evening. 
The most appropriate height of the windows is 5.5 to 1.5 meters from the ground. If higher distance is more suitable, it is better to use horizontal windows with joint and upward openers so that it leads the wind to downward (the room).
It is almost necessary to set up windows netting in order to prevent insects' entry to the room. Of course the netting reduces natural conditioning and wind stream inside the room. To reduce such a stream, the netting are set up wit some distance from the window and does not stick to the window. 
The windows and big openers in humid areas should effectively be protected against sunlight. The visors of the windows should protect the internal space not only against direct rays but also against scattered rays that have a quite considerable amount in tropical climate. In some cases it is possible to adjoin walls, windows, rain and sunlight protection by expanding the ceiling area. The method is mostly essential in the areas with downpour and wind in which the wind directs the rain horizontally and causes rain penetration to splits and cracks. 
3) The selection of building materials according to tropical climate
Due to the lessening of temperature fluctuation in tropical climate, high heat resistant and materials without heat capacity are the best ones. 
4) The effects of climate on buildings in tropical area
The effects of sun radiation in east and west require the buildings to have a tense format and cubed rectangle shape and locate at the east-west axis. This method is quite useful in making a stream inside the house and lessening humidity. If the building is located in shadow, the plan could be open and free.

Specifications of architecture in warm and dry areas

The local architecture in tropical area provides some problems as follows, for the people of the area for which they look for some solutions:
· Burning sunlight and hot 
· High temperature in day and low temperature at night 
· Daily temperature fluctuation particularly in summer 
· Hot summers and cold winters
· Dry weather, low rain and shortage of water
· Dusty and hot storms and perhaps sandy
1) Natural forces effective on building design in dry and warm areas
1-1 Sunlight
The sunshine is severe in this area and the energy of radiation increases for 700 to 800 kilocalorie per hour in the barren area. The sky is cloudless most of the year. Since sun radiation scatters by contacting aerosols or return toward sky by hitting clouds, the energy potential decreases while passing through atmosphere. Of course the proportion of scattered to direct radiation depend on cloudy condition of weather. 
The total heat reaching the ground is so much less in cloudy days compared to sunny days in which heat absorption is high. 
Nonetheless mist, fog and dust are generated in the afternoon and due to the movement of air layers next to the earth. Slight humidity and cloudless sky lead to the increasing of weather changes in the region. The ground temperature increases up to 70˚ centigrade in summer while the temperature rapidly decreases at night and reaches to 15˚ centigrade or even less. Of course weather fluctuation is less than this. Anyway the changes are within 20˚. The temperature reaches to 40 to 50˚ centigrade in a day and 15 to 25˚ centigrade at night. 
The shaping and directing buildings' surface for reducing effects of sunlight
The sun radiation absorption by buildings' façade could be minimized by different means:
1 Shaping and directing the building according to the sun
2 The height of the building facing sun
3 Shape and slope of the roof
Controlling the shadows in the façades, the shape of the plan, direction and height of the buildings could reduce the heat transition. 
The shape of the plan and orientation
By orienting the four sides of the buildings' toward four geographical directions (north, south, east and west), the absorption of sun radiation could be decreased. The perspective of the plan should be selected in a way that heat absorption from northern and southern façade would be equal to heat absorption from eastern and western sides in hottest season. The favorite perspective differs in latitudes. 
The height of the building
The height of the building is influential on the absorption of sun radiation since height increase leads to the increase in building façade consequently more area faces the sun. Since sun radiance is more on horizontal surfaces than vertical surfaces, so it is better to decrease roof surface and increase walls' surface. 
Additionally providing shadows for walls is so much easier than providing shadows for the ceilings. Generally speaking similar area buildings in southern area should be built higher than northern area in order to control sun radiation. 
If insulator or conditioning and splashing water on the roof decrease heat absorption, two-story building may enjoy more heat transition. It is because of the fact that two-story buildings have more façade than one-story buildings. 
The proportion of ceiling to wall is more important because of the significance of coldness in the building. 
The shape and slope of the roof
The effects of sun radiation on the shape and slope of the roof depend on the radiation angle. When radiation angle is high, all kind of similar area ceilings get equal heat. 
If radiation angle is minor, more inclined roofs get higher heat. This is very important for east-west towers. 
The lower roof layers are more important than roof shaping. The flat roofs are difficult to condition while inclined roofs are easily conditioned. Chimneys can be used for this purpose. If roof color is light or it is cooled by evaporation or if there is a suitable heat insulator underneath, the shape of the roof will loose its significance.
The quality of radiation surface
The amount of sun radiation on the surfaces locating in different directions varies. Anyway heat absorption on a surface not only depends on the direction but also on color, context (the degree of luster) and also the speed of air stream throughout the area. 
The amount of the heat conversely relates to the degree of color lightness and the speed of air stream. Additionally the more coarse and rough the area, the more heat absorption. 
The color of the surface is the most important factor affecting heat amount of a surface. 
The effects of color on the amount of heat absorption on a surface
Before sunrise, the change of heat in external surface of a building in all directions is concordant with the change of external air temperature. Then roof temperature is a few degrees less than outside temperature due to the reflection of rays with high wavelength. But after sunrise and when sun is directly shining from other surfaces, the temperature of external sides of the buildings increases in conjunction with the heat absorption. 
A light surfaces absorbs less energy and therefore is not that much hot. And the environment temperature mostly influences the heat. But when the color is dark, the effect of sunlight on generated heat is more than the effect of environment heat. 
1-2 The Wind
Some flows of Atlas Ocean winds blowing from northwest produce dusty storms in east of Iran and make the pebbles of Sarakhs, Torbat Jaam and Sabzevar move. Some part of the flow moves toward Gonabad. It is known as Herat Wind and generates a lot of dust in the region. Other flows of Atlas Ocean winds blow from Turkistan toward east of Iran and some part of Afghanistan. The speed of this stream is so much in some parts of Iran. The wind is known as "Systan 120-day" wind. It passes from Ghaenat and Ghonabad and goes toward Systan and then to Low-Pressure center in north India and Pakistan and south Iran. 
The mentioned wind is called "Lovar" in Systan and blows permanently during the summer and with different speeds. 
The initial speed is 36 kilometer per hour and then increases to 70 to 90 and even 108 to 120 kilometers per hour. The suitable predictions of the location of alleys and streets in tropical climate and directing them toward the wind, attracts the cold wind to the city and chills the city. 
Planting trees should prevent the hot winds and sandy storms. Pines are a good way if planted together due to the green color. But tamarisks are the best choice. In some of Khorasan villages, windmills do the same thing. 
In tropical areas, the natural conditioning should be minimized because internal temperature increases due to outside warm air entry to the inside area. During the day due to high wind speed, natural conditioning is more. 
Inside temperature change occurs in the layers closer to the outside air. On the other hand, body temperature could go down via vascular evaporation cause of humidity shortage. Consequently there in no need for speedy air to achieve cool down via evaporation. The speed of 15 cen/sec could be enough for this purpose. 
The speed is generated because of heat difference and penetration of outside air through windows’ fissures. There is no need for opening the windows. 
During the evening and at night natural conditioning rapidly cools the inside area down because of lower outside temperature. The necessity of air stream at night and in the evening, makes us to open the windows. 
Nether buildings get a little dust and sand in dust and sand storms. It is because of the fact that in the exaltations more than 15 meters, the amount of sand considerably decreases. 
In contrast to clement and humid areas, attempts are made to prevent storm and entrance of outside air through windows particularly in warm weather. Instead other arrangements such as vents are predicted to cool the area.
The veranda provides a half open space that can be used during summer.
Vent
Vents are one of the signs of dry and warm climate cities. Kashan and Yazd have examples of those.
Vents are usually located in an area so that they cool the house and terrace. Vents are mostly set up in the most occupied rooms. 
The vent is set up in the middle of five-door-room or in the hall.
There is also a connection with the basement. The opening of the basement is wider under the basement. The small air stream moves to the basement via the opening and pulls up by one or two suctions.
There are many of such vents in Yazd. Of course we can also witness houses that are cooled without vents. That is a ventilator is set up in a four sides house. The ventilator not only sends air stream to the house but also provides more lightening.
There are one side, two-side, 3-side and 4-side vents concerning the direction of the wind in different regions in the country. We can see one-side vents in cities with the zephyr with define direction.
Since the direction of the thunderstorm and cold wind are opposite, when the thunderstorms blow behind the vents, they aspirate the wind inside.
In such closed assortment, which there is no airflow, air circulation is being done by the means of the vent installed behind the terrace of the house, which intercommunicate with the terrace and in some cases with inferior basement.
The process of the vent is on the basis of aspiration the fug inside the building blowing the frost out by the use of reaction of it.
If the wind smashes the walls of the vent’s inner ribs, it pulls down, but the other rifts of it, which are backing the wind, direct the polluted air toward wind.
Shaping and directing building facade in order to maximize summer breeze:
The longest side the building should vertically lie on the direction of the zephyr in order to get the best air conditioning. If the angle between the building and wind were more or less than 90˚, the conditioning would be done better. Anyway wind direction diverts ninety-degree angle is suitable. If the strongest winds` direction is not clear i.e. the wind is blowing from all sides, the building should be designed so that air conditioning would be possible from both sides. The best plan is a square shape building with some windows locating in the four sides.
When the direction of the strongest wind is clear, the shape and direction of the building should be in away that air stream could pass through the building. 
Therefore L shape plans are not appropriate. Air pressure is more in the façade of high building that are facing the wind, thus conditioning would rapidly be done. 
Vertical positioning of the rooms facilitates air stream and leads to dual conditioning. Increasing the height of buildings is a traditional way of getting the best conditioning. 
2-The effects of climate on the buildings’ façade in warm and dry areas
Natural air conditioning should be minimized during the day in warm and dry area, because warm air entrance increase inside temperature. During the evening and at night, lowering of outside temperature provides the best conditioning, and inside room temperature cools down.
Enough consideration should be given to the fact that conditioning efficiency does not relate to the size of windows. 
Heat absorption from windows could be minimized by coordinating location, shape and opening method of windows. That is small size windows could contribute to useful conditioning. Additionally, the shape and dust entry to the building should be considered. 
Buildings locating on the underneath absorb less dust in thunderous areas, because the amount of dust falls down in higher areas. 
Large verandas are located toward cool streams in warm and dry areas; those verandas provide a favorite weather in the afternoon. 
3-Selection of building material in conjunction with warm and dry climate
For many centuries, adobe and mud have been the main materials used for constructing buildings of warm and dry area. The material is generated by mixing soil and water, and kneading it. Soil cement is used in muddy and adobe rural buildings. The more the clay, the more the viscosity and cracks after drying. 
Soil cement is used as a cover. It is better to add some salt to the roofing mud to prevent rain penetration. Salty mud paste slowly looses water and does not freeze in a few temperatures below zero. This constructive material is easy to make and is used wisely. 
The light color of mud reflects the sun heat. As a result the heat does not enter the building. 
The temperature difference between day and night necessitates careful material selection. It is better to use light materials in construction of the parts of the building mostly used at night. For the parts used in a day, heavy materials are the best choice. 
4-The effects of climate on building format in dry and warm areas
The best format is the one in which the less amount of heat is lost during the winter and the most is absorbed during the summer. 
Therefore there was a common idea that square shape building is the best to keep the heat in winter and cool the house in summer. 
Square shape buildings are required to be longer in winter season of warm and dry climate (toward east and west) but if summer is the most dominate season, the square shape is the most suitable one. 
Some part of the building can act as a yard that provides shadow. Trees can be planted there and a pool can be set up. That way the weather can be cooled down by evaporation via tree, grass and pool. Veranda creates a half-opened space in terrace which was used while sun raised up the opposite wall in summer afternoons. Ceiling of the veranda was built two three steps higher than the surface of the yard. In this difference between yard and veranda, basement vents located under the terrace were foreseen. Basement was usually located under veranda and in-between Five-Door. This part was the most desirable space to take rest in warm afternoons of summer. 
Domed roofs 
Domed roofs are always exposed to blowing breezes due to their pop up forms. This would cause decrease of heat when sun shined on roof. During nights heat reflected from the roof would remove faster. In Iran’s architecture problem of cooling the inner space was better solved with two-shielded domed roof invention. 
Isolation of the space between the two shields, made the internal shield cooler. This is more seen in architecture of public places where transportation of people was more. 
Iranian architects were always looking for better solutions to keep cool in warmth of summers and cold of winters. 
From geometric point of view, the area of an over arch is approximately three times bigger than its base area. So intensity of sunshine would be decreased on the round part. And the lower part of the domed roof would attract even lesser temperature. On the other hand domed roof are always exposed to blowing breezes and that is why summer heats would affect them less comparing to flat roofs. The domed form is also suitable for exiting temperature during nights and helps cooling the area. It means that the heat returned from frame of the building is also gone away. 
Two-layer dome
Two-layer dome having different types acts as follows:
1- The space between two layers act as isolator and make the internal layer cooler against warmth of the external layer attracted by sunshine. 
2- Internal layer of the domed stalk particularly in tower domes connects together on top and prevents splitting of column stalk in the basement of external layer due to horizontal drift pressure generating from heavy external layer. 
3- The space under the domed roof is harmonized by structure of internal layer while external layer gives building a good look from outside.
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