Climatic design of form, aspect ratio and building’s orientation based on solar radiation in Tehran

Considering the special geographical-climatic conditions and the high consumption of fossil fuels in Tehran, the design of buildings, consistent with the climate and in order to benefit from renewable energies such as solar energy is necessary. The physical characteristics of buildings have a very important role in the regulation of microclimate conditions and thermal situation of interior and exterior spaces of buildings. The aim of this research is to determine the proper form, aspect ratio and orientation of buildings, based on the amount of received solar radiation in Tehran. In this research, six geometric forms, including square, rectangle, hexagonal, octagonal, hexadecagon and triacontadigon with an equal area and elevation were studied. Using the Q-BASIC software, the azimuth angle and altitude of the sun were extracted, then, based on “Law of Cosines” computational method, the amount of energy received at the vertical surfaces was estimated in 32 geographic directions. The results show that the highest amount of annual received energy is related to the rectangular form with the North-South orientation and the least amount is related to the rectangular form with East-West orientation. The best form of building in Tehran is a rectangle with East-West orientation and after that is the square form. The most suitable aspect ratio for the rectangular form with the East-West orientation is the ratio of 1: 1.4. The most appropriate orientations for the specified aspect ratios, are the 165 degrees South-East and South-West and then is the directions to the South.