"Dowlat abad" Garden (17th century)
Comprising a large garden and some buildings, the "Dowlat abad" Garden is a famous complex built in the original Iranian style which was watered by a qanat of the same name. In the past, it was the residence of the governor. The most impressive part of this complex is the main building, that is an example of Outward-Looking houses in Yazd, with a complete ventilation system. The main part of this system is the very tall badgir (opposite) with a hieght of 33.35 m and an octagonal plan. This badgir catches cool winds at a higher level, in all directions, and channels them into the interior spaces. The dry and warm wind will pass over a pond with a fountain gets cool and wet through evaporation. Then the cool and wet air flows in the room. There is an increase in air pressure to windward and decrease to leeward, so the badgir will catch the windward air and sucks the interior air to leeward, thus ventilating the interior.
The badgir's material again plays another role, the temperature differences between day and night is quite high in this climate, the day 35°C and night with 17°C, so they use this high fluctuation of temperature. At night time when it is cold the badgir, which is made with mud-brick, gets cool by radiation and convection.
The mud-brick has 7 to 9 hours response time So in the morning it begins to give its coolness to air so the internal air becomes cold and because of its high density, flows down in the rooms.
This happens in the morning. The wind shaft gets warm during the daytime, at night it works as a solar chimney, the walls will give their heat to the air, with that delay, and the internal air decreases in density, rises and sucks the air in the room. Cool air will then replace warm air in the room. The system works, when there is no wind, but when wind is blowing this system does not have problems. Because during the day, if there is wind, then cool air flows faster and at night, with wind, it may absorb the heat of the walls, because the night wind is cool enough.
The air movement in an Outward-Looking house.
The main part of this system is the very tall badgir with a hieght of 33.35 m and an octagonal plan. This badgir catch cool winds (1) at a higher level, in all directions, and channels them (2, 5) into the interior spaces. The dry and warm wind (5) will pass over a pond with a fountain, and with evaporation gets cool and wet. The cool and wet air (6) then flows in to the room. There is an increase in air pressure to windward (1) and decrease to leeward (3), so the badgir will catch the windward air and suck the air to leeward, thus ventilating the interior.
The main hall and the pond under the dome
This building has a dome on the central hall, that helps ventilation, the warm air rises up under the dome and goes out through its vents, it happens by stack effect without any wind, but if there is wind, the wind encourages ventilation in two ways. First, the wind on the dome causes a negative pressure near the passages and this negative pressure sucks air. The air (8) comes in through the big windows passing ponds and a garden, this is another aid to ventilation. Again as described for the badgir the same thing will happen in cold nights and warm days.
The effect of sun on this dome is useful too, during the day sun shining on this dome and makes it hot, this heat will transfer to surrounding air by convection and radiation, so this air will heat and rise up and give its place to cooler air, so the air flows into the building. The last strategy used here to cool the system is vegetation around the building. They cool and give oxygen to the air. And this fresh air will go through the system.
