A solar chimney is a hot air channel attached to the roof. It enhances natural ventilation for buildings by employing the temperature difference of air at the inlet and the outlet of the channel. Experiments were carried out in an open-ended air gap, situated between the corrugated roof tile and the gypsum board, with the tilt angle of 45° of the testing building. The results showed a reduction of temperature differences between the inlet and outlet of the solar chimney for all of the daytime, implying a decrease of volume flow rate of air in the system. The hot-surface, inlet air, and outlet air temperatures were observed to increase during 8:00-12:00 and they decreased rapidly during 13:00-17:00. We obtained an empirical equation relating the Nusselt number, Rayleigh number, and the dimensions and angles of the roof. Because the equation is derived from the field experiment under the hot and humid climate, it could be used for the determination of the mean convection heat transfer coefficient of a roof solar chimney with a similar geometry.