The courtyard buildings, which we face either as a regulator of inter-building microclimate or as a climatic regulator at urban scale especially in hot climate regions, and which constitute one of the fundamental characteristic building styles of such climatic regions, should be applied in a form compatible with the features of the climatic region it is used. There is the need for a study that allows formation of a model toward determination of the optimum courtyard form and meeting the conditions of comfort by establishing an optimization model taking into consideration the climatic, meteorological differences for each climatic region the specific climatic region requires. The purpose of this study is to examine the energy efficiencies of the courtyard buildings used either as a micro climatic regulator in hot-dry climatic regions, or as a climatic regulator at urban scale, and to determine inter-building and courtyard comfort statuses, besides, to manifest different thermal behaviors of such buildings by estimating the same fully and accurately using real meteorological data under different design and climatic conditions with computer energy simulation on different courtyard form options put forth for different climatic regions, and thus to provide new information to designers at the process of putting forward the optimum courtyard form according to the characteristics and data of the specific climate for different climatic regions. By using the CFD program, this study has analyzed the thermal comfort statuses and energy performances of 7 different courtyard shapes in inter-courtyard and building volumes that are discussed in hot-dry, hothumid and cold climatic regions as well as the effect of the sunbeams received by the building surface and the daily solar movement on the thermal performance on the building. As a result of the entire analysis made for all building shapes, the obtained values were interpreted and the total energy performances were evaluated for each climatic region. In this study, the courtyard buildings will be assessed in terms of their thermal performances. (C) 2014 Elsevier B.V. All rights reserved.