It is acknowledged that roof top made of PV cell could improve the surrounding environment when it is compared to conventional roof top that made of concrete. PV cell can converts solar radiation into electricity and as the consequence the remaining heat is lesser than that of the concrete roof. Based on this principal theory, this study focused on investigating the level of irradiance of a roof top made of PV modules. The construction process of the PV modules was conducted through simulation and parametric study in order to obtain not only an optimum irradiance level, but also to create an aesthetic form. In order to facilitate that objective, this study consists of 3 steps: (1) to determine the required parameter, (2) to construct all the required parameter into an algorithm and (3) to execute the constructed algorithm. The initial flat roof form was used as the basic form. The results show that the average shaded area of the final form is only 3%.