This paper presents a computer model was developed to examine the thermal performance of courtyard forms in different climatic regions. It is based on understanding the interaction taking place between the sun at any time during the year and the courtyard geometry. This computer model allowed detailed investigation to be carried out into the effect of geometrical and physical parameters of different courtyard forms on the solar radiation received on their surfaces. The program was developed to allow this investigation to be undertaken easily and to avoid the lengthy computations involved. Also, it fulfils the shortage in some well-known computer packages in terms of calculating numerically the shaded and sunlit areas in different courtyard geometries. It was designed to investigate the most commonly used courtyard geometrical shapes (in plan) in different regions of the world, which are rectangular, pentagonal, hexagonal, heptagonal, octagonal and circular. The input of the program is the geometrical and physical parameters of the courtyard and the data of the sun’s position. While the output is the floor and walls shaded and exposed areas, and the solar radiation received on the internal surfaces. The program was validated through testing its results against real measured data and the results of available software. The validation process showed a high degree of validity and reliability to the developed model.