Abstract There is increasing concern about environmental pollution and the need for efficient energy sources. Thus, natural ventilation using renewable energy without the need for mechanical devices has gained great importance. A shavadoon is an example of a natural ventilation system used for cooling and heating in Dezful, a warm and semi-humid city in Iran. They are constructed at a depth of 5–12 m and utilize the high thermal capacity of the soil to have about 20 °C temperature below the ambient temperature during the hottest days of summer. In this study, the effect of shavadoons’ components like kat (a chamber of the main room, which is called the sahn), foot rest, and shabestan (a type of basement that connects the shavadoon to the main building) that can increase the volume of the stored air are investigated on natural ventilation and an ideal shape of the shavadoon is found. The results show that although adding the kats adjacent to the sahn (making the shavadoon’s cross-sectional area from simple form to a cruciform) can increase the storage cold air during the night, the backflow in stairway is increased and ventilation rate is decreased. In addition, foot rests were found to increase the inlet air flow and a four-fold increase in the foot rest volume, increased the air flow by 12.5%. Shabestan on the upper floor of the shavadoon enhances the inlet flow and improves the ventilation rate, although the shabestans are not used on hot summer days due to temperature fluctuations. So, shavadoons without Kats and with larger foot rests can be chosen as an optimal shape of Shavadoon.