The dynamic heat transfer between two half-spaces separated by a vacuum gap due to the coupling of their surface modes is modeled using the theory that describes the dynamic energy transfer between two coupled harmonic oscillators, each separately connected to a heat bath and with the heat baths maintained at different temperatures. The theory is applied for the case when the two surfaces are made up of a polar crystal that supports surface polaritons that can be excited at room temperature and the predicted heat transfer is compared to the steady-state heat transfer value calculated from the standard fluctuational electrodynamics theory. It is observed that for small time intervals the value of heat flux can be significantly higher than that of steady-state value.