This paper describes the results of radiant exergy analysis on the process of human adaptive thermal comfort in summer. A subjective experiment controlling not only indoor thermal environment but also their clothes and posture for removing discomfort was made in 2016 summer. We found that subject's adaptive thermal comfort is related to their cognitive temperature and warm radiant exergy from the interior surface of buildings envelopes. To decrease warm radiant exergy by behavioural controls such as opening the window and the door, and controlling the venetian blind is to decrease their cognitive temperature of the subjects.