Window, comprising at least the following features: a. a window frame composed of a plurality of frame profiles, b. a sash frame composed of a plurality of frame profiles which has at least one surface element and which is movable relative to the window frame at least between a closed position and a ventilation position, c. wherein a continuous frame rebate space is formed between the frame profiles (1', 2') of the window frame and the sash frame, d. at least one ventilation duct formed in at least one of the frame profiles of the window frame, which has a first ventilation duct opening and a second ventilation duct opening, e. wherein the sash frame and the window frame are designed to close at least one of the ventilation duct openings (9, 10) in the closed position and to open both ventilation duct openings (9, 10) of the at least one ventilation duct in the ventilation position, f. wherein at least two sealing layers are formed between the window frame and the sash frame in the region of the frame rebate space in a closed state, g. wherein one of the sealing layers is formed by a center seal between the window frame and the sash frame, h. wherein the center seal has a sealing base and a sealing section pivotally attached to the sealing base, characterized in that i. at least the at least one frame profile of the window frame in which the at least one ventilation duct is formed is designed as a multi-chamber hollow profile which consists entirely or substantially of plastic, wherein the walls facing the adjacent spaces (I; II) of the window consist of plastic, and j. a sliding strip is arranged on the sash frame on one of its multiple frame profiles, against which the center seal rests in the ventilation position, wherein the sealing section, in the region or regions in which the respective ventilation duct is formed, rests at its free end against the contact sliding section on the sliding strip and thus divides the frame rebate space in a sealing manner. a. a window frame composed of a plurality of frame profiles, b. a sash frame composed of a plurality of frame profiles which has at least one surface element and which is movable relative to the window frame at least between a closed position and a ventilation position, c. wherein a continuous frame rebate space is formed between the frame profiles (1', 2') of the window frame and the sash frame, d. at least one ventilation duct formed in at least one of the frame profiles of the window frame, which has a first ventilation duct opening and a second ventilation duct opening, e. wherein the sash frame and the window frame are designed to close at least one of the ventilation duct openings (9, 10) in the closed position and to open both ventilation duct openings (9, 10) of the at least one ventilation duct in the ventilation position, f. wherein at least two sealing layers are formed between the window frame and the sash frame in the region of the frame rebate space in a closed state, g. wherein one of the sealing layers is formed by a center seal between the window frame and the sash frame, h. wherein the center seal has a sealing base and a sealing section pivotally attached to the sealing base, characterized in that i. at least the at least one frame profile of the window frame in which the at least one ventilation duct is formed is designed as a multi-chamber hollow profile which consists entirely or substantially of plastic, wherein the walls facing the adjacent spaces (I; II) of the window consist of plastic, and j. a sliding strip is arranged on the sash frame on one of its multiple frame profiles, against which the center seal rests in the ventilation position, wherein the sealing section, in the region or regions in which the respective ventilation duct is formed, rests at its free end against the contact sliding section on the sliding strip and thus divides the frame rebate space in a sealing manner.