Previous studies have mainly focused on investigating the optimum orientation of the buildings, in terms of solar radiation accessibility, regardless of the distribution of living spaces within the form. However, in many cases, the living areas of the building face an orientation other than the optimum. This occurs if a building is not of a unilateral type but where living areas are located in different directions. The most common type of building is the bilateral one where the living areas are located in opposite directions. In the bilateral design of buildings, the insolation of opposite facades in a way that assures the access of sunrays to all residential units located in both sides of the form is crucial. As was proved by previous experiments, the north facade of the rectangular forms (elongated east-west) receives no sunrays at all in wintertime in Jerusalem. This situation provides advantages to units located to the south side and undermines the northern ones. The radial form might be the solution to this problem because it receives winter sunrays on both facades. As the main feature that determines the shape of the radial form is the extension of the concavity, it was necessary to compare several types of radial form with various extents of concavity in order to find out which one could be more suitable for bilateral types of building.