Energy Efficient Architecture

Abstract

A building enclosure in its own right is a modifier of the outdoor environment and its main objective is to provide conditions for comfortable living for its inhabitants. This objective is often met by air-conditioning. So, an important parameter that specifies a building is its energy demand. The fact that the sun’s energy can be utilized for natural heating and cooling of indoor space in a building was recognized even by ancient people. The shape, location and orientation of buildings were considered to be effective in modifying climate to achieve thermal comfort inside a building. In 400 BC, Socrates pointed out the importance of the summer to winter variation of the penetration of the sun’s rays in south-facing porticos. This can be considered as the starting point for the natural heating and cooling of buildings. From 900 AD, building cooling methods based on the ‘wind tower’ and ‘air vents’ were in vogue in Iranian architecture. The underlying principle of the wind tower is as follows. The arid region of Iran has a fairly stable wind pattern; it has hot, strong winds in the day and almost no wind in cold nights. During the day, the wind induces downward motion of air in the tower since the air becomes cooler as it advances downward either because the tower interior has been cooled on the previous night or is being cooled by a water fountain and plants. The cool air is circulated through the rooms in the building by suitable operation of doors, windows and ventilators. During the night when there is no wind, the walls of the tower which were heated during the day transfer heat to air in the top region of the tower and induce circulation that carries cool night air through living rooms and up through the tower. The cooling of air in the above process is essentially ‘sensible cooling’. In later cooling configurations, the wind tower is placed some 30–50 m away from building and is connected by a tunnel. The air coming from the tower is moistened by water droplets in the tunnel which is damp owing to watering of trees and grass above it or due to inbuilt fountains or pools. The vapourization of these droplets removes a large amount of heat from the air thereby cooling it. This is referred to as ‘evaporative cooling’.