This paper investigates the influence of solar radiation on thermal comfort inside an indoor environment and its effect on the building energy consumptions. Furthermore, it draws up a procedure which allows the rating of the thermal comfort quality of indoor environments in the presence of solar radiation, to be used in correlation with the energy classification of building in order to refer the energy performance to the indoor environmental conditions. Mean Radiant Temperatures (MRT) for a subject exposed to solar radiation in different positions of the environment were calculated, with an hourly time step and for a whole year. These values were utilized to assess the Predicted Percentage of Dissatisfied (PPD) and its variation with time and space, so that long term thermal comfort evaluations were able to be carried out and comparisons among irradiated and not irradiated positions were able to be made.