Radiative heat losses represent a substantial part of the total balance of the human body in a closed space. The correct determination of this contribution is necessary in order to gain an insight into the influence of this parameter on human thermal comfort. The thermal balance is strongly affected bysurface temperatures and by the angle factor between a body and a wall surface. Since a room's internal surfaces are composed of various parts, the calculation of view factors becomes more complex. Therefore, a computer algorithm is a useful tool for determining the radiant heat exchange, particularly for the complex surface compositions, encountered in practical situations. The proposed algorithm is based on the computation of view factors, which are additive. This algorithm enables the computation of view factors for composite surfaces, thus allowing for the complex impact of view factors on thermal radiative heat exchange, as is the case for the seated posture and other orientations of the human body. The matrix-based approach makes it possible to determine the influence of various parameters on the mean radiant temperature.