Kapetanova Kula is situated in Old city core of Bihac, and it is proclaimed National monument under governmental protection. Today’s condition of the monument is poor due to serious destruction of the façade by the atmospheric waters. The project covers repair of the walls from both sides, substitution of openings, amendment of roof covering, major changes in ground floor (pavement and partition). Currently, this monument is transformed into a museum. It is important to have perfect condition for artefacts as well as for the building itself. That is why, we proposed the system of ventilation and heating. Main source of energy would be water/water heat pump and ventilation unit would be placed under the roof.