The thermal behavior of the inside air of a closed Venlo glasshouse without plants was analysed under semi-arid climate conditions. The aim of the study was to investigate to what extent the characteristics of the greenhouse design and outside climatic conditions influence airflow and temperature patterns inside the greenhouse. For the purpose of the present work, a CFD modeling approach was combined with field surveys. The study focuses on the effects of (i) the thermal inertia of the soil, (ii) the movement of the interior air, and (iii) the distribution of the temperature inside the greenhouse. Two contrasted days were considered: a windy overcast day and clear day. From the results, it is concluded that when the greenhouse is fully closed with bare soil, the heat absorbed and stored by the ground during daytime represents a significant heat source which enhances buoyancy forces, the main driving forces of the movement of the air, especially during the night. The temperature of the roof was relatively low and the air temperature distribution inside the greenhouse disclosed a vertical gradient from the roof towards the ground surface due to the movement of the air above the surface of the ground absorbing thermal energy (solar energy). Maximum air velocities inside the greenhouse were observed near the ground surface, while they reached their minimum values in the middle of the greenhouse. Similar results were obtained for the windy overcast day and for the clear day.