We consider heat transfer processes where radiation in a large number of frequency bands plays a dominant role. In the simulation of such processes, the radiative transfer equation has to be solved repeatedly. To obtain an efficient and accurate solution method, we propose a new hybrid algorithm which combines fast solvers for the radiative transfer equation in the low and high absorption regime, respectively. A key role is played by an exact, residual based error formula. The algorithm is applied to a cooling problem of high quality optical glass.