A ventilation device for aerating and deaerating rooms of a building, comprising a housing arranged in a building wall of the building having a first side face towards the rooms' interior of the building, which, at a lower level , has an outlet opening for the aeration media flow of a first lower airflow channel and an inlet opening for the deaeration media flow of a second lower airflow channel , and having a second side face towards the exterior of the building, which, at an upper level , respectively has inlet and outlet openings for the reciprocal aeration and deaeration media flows of the upper airflow channels , having a heat storage unit for transferring heat from the deaeration media flow to the aeration media flow , an air-conveying device , comprising a supply air fan for the aeration media flow and an exhaust air fan for the deaeration media flow , which are continuously operated in an air-conveying direction, and having a closing and opening device for controlling the airflow, characterized in that the housing , separated by an intermediate bottom at a height (H), forms the upper level and the lower level , wherein the housing , at a length (L), is divided by the closing and opening device at the upper level and by means of separating walls at the lower level , forming the two upper airflow channels and the two lower airflow channels , wherein the supply air fan and the exhaust air fan connect the upper level with the lower level , and the upper airflow channels towards the second side face of the housing respectively have a heat storage unit at the upper level and a supply air filter element is respectively allocated between the heat storage unit and the exterior of the building, wherein each supply air filter element in the airflow channels can be flowed through reciprocally and inversely by the aeration and deaeration media flows by switching the closing and opening device , and wherein the airflow channels at the lower level are consistently flowed through by the aeration and deaeration media flows , wherein an exhaust air filter element is arranged towards the first side face of the housing in the area of the inlet opening of the second lower airflow channel , which is permanently flowed through by the deaeration media flow . the housing , separated by an intermediate bottom at a height (H), forms the upper level and the lower level , wherein the housing , at a length (L), is divided by the closing and opening device at the upper level and by means of separating walls at the lower level , forming the two upper airflow channels and the two lower airflow channels , wherein the supply air fan and the exhaust air fan connect the upper level with the lower level , and the upper airflow channels towards the second side face of the housing respectively have a heat storage unit at the upper level and a supply air filter element is respectively allocated between the heat storage unit and the exterior of the building, wherein each supply air filter element in the airflow channels can be flowed through reciprocally and inversely by the aeration and deaeration media flows by switching the closing and opening device , and wherein the airflow channels at the lower level are consistently flowed through by the aeration and deaeration media flows , wherein an exhaust air filter element is arranged towards the first side face of the housing in the area of the inlet opening of the second lower airflow channel , which is permanently flowed through by the deaeration media flow . <EOS>