The exposed surface area of a building is related to the rate at which the building gains or loses heat, while the volume is related to the ability of the building to store heat. Therefore, the ratio of volume to exposed surface area is widely used as an indicator of the rate at which the building heats up during the day and cools down at night. A high volume-to-surface ratio is preferable for a building that is desired to heat up slowly because it offers small exposed surface for the control of both heat losses and gains (Dimoudi, 1997).
Building shape and orientation must be chosen in such a way so as to provide both heating and cooling. For heating, the designer must be careful to allow solar access, i.e., allow the sun to reach the appropriate surfaces for the maximum possible hours, especially during the period from 9 am to 3 pm, which is the most useful energy period. For cooling, breeze and shading must be taken into consideration. The theoretical solar radiation impact for the various building surfaces can be obtained from appropriate tables, according to the time of the year and the surface orientation. From this analysis, the designer can select which surfaces should be exposed to or protected from the sun. Generally, south walls are the best solar collectors during wintertime but, together with the roof, they are the most problematic in summertime. With respect to shape, the best is the rectangular one with its long axis running in the east-west direction, because the south area receives three times more energy than the east or west. A square shape should be avoided, as should the rectangular shape with its long axis running in the north-south direction.
One way to control the solar radiation reaching the building is to use trees that drop their leaves during winter in the sunlit area, such as south of the building. In this way, the sun reaches the surface in question during winter but the surface is in shade during summer.
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