In Tunisia, the buildings’ space heating sector represents a major part of the total energy consumption budget. These issues have been increasingly prominent concerns since the energy crisis. Hence, interests have been growing to adopt renewable energies as viable sources of energy that offer a wide range of exceptional benefits with an important degree of promise, especially in the buildings sector. However, the management of renewable energy sources for space air heating/cooling is usually not economically feasible compared with the traditional carriers. In this chapter, we present a passive energy system, called air-conditioning cupboard which exploits renewable energies (hot water supplied from solar collector [40-50°C] and cold groundwater (19°C)) as thermal sources, is conceived and tested in our laboratory (Laboratory of Thermal Procedure, LPT Tunisia). To evaluate the air-conditioning cupboard efficiency indoor experiments were carried out under varied Tunisian environmental conditions for several days. Results show that the air-heating system has good thermal effectiveness (80 %). It permits to the maintenance of the temperature inside the experimented room at the range of [24-27°C] during the cold months and [20-23°C] during hot months. A theoretical model is employed for the sizing of the air-conditioning cupboard to obtain the required temperature values. This model allows also the determination of the air-cupboard conditioning thermal performances.