Natural ventilation is an important means to improve thermal comfort conditionings and to reduce the energy consumption for residential buildings. Solar chimney system can be used to enhance the natural ventilation effectiveness, which can make full use of solar energy to produce upward momentum to a mass of air, thereby converting the thermal energy into kinetic energy. In this paper, a numerical study has been carried out to predict mass flow rate, temperature field and velocity field for vertical roof solar chimney under steady-state conditions. Suggestions for optimum construction design of solar chimney have been put forward based on large numbers of simulation results. Results showed that for vertical roof solar chimney with both ends open, the optimum gap-toheight ratio 1/2 was found in the range of chimney gaps investigated, compared with Trombe wall optimum ratio 1/10. The predicted ventilation rate increases with solar radiation and solar chimney height. Meanwhile, reverse flow can be observed at the outlet when the chimney gap increased to a certain value. These findings are helpful in designing a natural ventilation solar chimney for residential buildings.