Figure 3.9 Insolation levels and orientation

The buildings in the northern latitudes, where the air is generally cool, should be oriented to receive maximum amount of solar insolation. In the south latitudes, characterized with warmer air, the building should be oriented to avoid the solar insolation and utilize the cooling local breezes.

In Figure 3.9a, the insolation levels are shown in the underheated period in the cold months, where the maximum levels are east of south. In the hot months, in the overheated period, Figure 3.9b the biggest sun gain is far to the west of south. The solution for the buildings` orientation is to position the main facade to the largest winter gains, while the buildings` shorter side facade is being perpendicular to the angle of the undesirable summer sun in the overheated period.

a) underheated period b) overheated period c) compromise orientation to 25° east of south

Figure 3.9Insolation levels and orientation[45]

A comparison of optimal building orientation relative to four climate types is given for buildings with predominantly one orientation.

 In the cool and temperate regions the optimal orientation is south or inclination of 20° to west or 40° towards east, with 12° to the east are optimal.  In the temperate region the inclination can be 15° and up to 45° to the west and east respectively, with 17.5° to the east are optimal.  In the hot-arid region the orientation should be towards south with inclination of up to 35°, with 25° towards east being an optimum.  In the hot-humid zone the orientation should be perpendicular to the axis of the overheated period, meaning the building can have an inclination of 5° to the west and 15° towards east, with 5° to the east are optimal.

Buildings with apartments back-to-back are unsuitable for southern latitudes and should be replaced by "through" typology of buildings where a same apartment has two opposite orientations. Such bilateral typologies have a large positioning range in the cool and temperate zones. With the rotation of the axis towards the west, the heat distribution on the sides will be equalized, but the west side will receive less sunlight. At most easterly axis positions, the west side should be protected from summer radiation. The back-to-back building type is unsuitable for more southerly latitudes and should be replaced by the through type of bilateral buildings.