Four design parameters: conditioned air flow rate, air-conditioning (A/C) outlet location, body vent location and glass properties were studied to evaluate their effects on passenger thermal comfort. By taking all these parameters into account, nine different cases were simulated for the steady-state cooling process in a simplified GM-10 passenger compartment. Three-dimensional air flow and temperature distributions for each case were obtained using VINE3D, which solves a set of partial differential equations governing mass, momentum and energy balance in the passenger compartment. Based on the computed air flow and temperature distributions, passenger thermal comfort was evaluated by Fanger's method.A/C outlet location and total system flow rate are the most important parameters which influence thermal comfort. The location of the exit vents also plays a significant role on rear passenger comfort. Considering solar load is the major heat source in the passenger compartment, the glass properties have a great potential to reduce it. However, currently available range of glass materials is narrow. In this study, the glass properties have a smaller effect on thermal comfort. The results of this study can provide useful guidelines for setting A/C system requirements during the early stages of vehicle design.