The numerical simulation of turbulent flow and heat transfer, when air moves around a thermal manikin sitting in a model room with mixing ventilation, has been carried out. The calculations were performed on the basis of the RANS approach using the standard k-ε turbulence model. The buoyancy effects were described in the Boussinesq approximation. The obtained calculated data were close to the experimental ones, although there were local differences in the temperature distribution near the surface of the room walls. The impossibility of correct determination of the integral heat removal from the surface of the body without taking into account the radiation heat transfer was established. Along with studies in the ventilation regime with predominant forced convection, corresponding to the experiment, the characteristics of the flow and heat transfer in the free convection regime were analyzed, where the flow structure being caused by an intensive thermal plume forming above the manikin, and the temperature field being stratified in height.