The city of Yazd has a large number of traditional houses. Houses with central courtyards and an Iwan were suitable for establishing thermal comfort conditions. In this research, the effect of Iwan's depth and the ratio of the adjacent room's openings on the comfort condition in the residential courtyard buildings in Yazd city were evaluated. The current research aims to provide an optimal model of the Iwan to increase sustainable development and use such models as the Iwan in contemporary housing in the hot and dry climate of Yazd. In order to investigate the effect of parameters, samples from the north-facing room and south-facing room in a central courtyard model with different proportions of the Iwan and different sizes of the window were simulated in Design Builder software. The results showed that the depth of Iwan and window to wall ratio's (WWR) of the adjacent room’s window significantly affects the comfort (according to cooling load, heating load, and energy consumption) in this room. The results obtained in this research will be a new window to recover the concepts of old patterns and help to solve climate problems.