This paper presents an investigation of the influence of surface radiation on indoor environmental parameters such as thermal comfort and indoor air quality. To achieve this objective, coupled heat transfer by mixed convection and radiation was numerically carried out inside a ventilated cavity. Air-CO2 mixture was considered as the working fluid. Uniform heat and CO2-concentration were applied at the bottom wall of the cavity. The boundary conditions of other walls were fixed at the external conditions. The same emissivity value was considered for all interior surfaces. An external fresh air enters at the cavity through an opening located on the top of the left vertical wall and exits from another one located at the bottom of the opposite wall. The mass, momentum, energy and chemical specie equations, coupled with the RNG k-ε turbulence model were solved via finite volume method. The obtained results indicate that the surface radiation presents slight effect on thermal comfort indexes, while the increasing of Rayleigh number enhances them. A good indoor air quality is insured inside the studied cavity.