Effects of Climate on the Form and Elevation of Buildings in Iran
Nazanin Salimi


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.