This paper analyzes the influence of solar radiation, considering both its direct and diffuse component, on the local thermal comfort of subjects in indoor environments. More precisely, an original equation for the assessment of the plane radiant temperature in presence of solar radiation is proposed. It can be used to evaluate the correspondent radiant asymmetry and therefore allows detailed analysis of local thermal discomfort conditions. Its reliability and feasibility have been tried out by means of an application to a simple case study and the obtained results proved that, in the studied environment, solar radiation affects the symmetry of the radiant field to a considerable extent, being the main cause of local discomfort due to not acceptable values of the radiant asymmetry. Therefore, the method can be used to verify the presence of zones not suited to human activities inside rooms and, in addition, it can be exploited by the procedures aimed at the classification of the comfort quality of indoor environments. (C) 2017 Elsevier Ltd. All rights reserved.