The invention relates to a flat element (1) for thermally adjusting indoor air, especially for cooling indoor air. Said flat element (1) comprises an air guiding chamber (2) and an active cover surface (3) having microholes (4). The air guiding chamber (2) has an upper side (5), a plurality of sidewalls (6a, 6b), at least one opening (7) for letting air in and at least one opening (8) for discharging air. The active cover surface (3) closes the air guiding chamber (2) towards its open bottom side. The upper side (5) of the air guiding chamber (2) is shaped so as to have at least one baffle (10) having at least one air guiding edge (11).