Building energy-saving fresh air system

The utility model discloses a building energy-saving type fresh air system which comprises a plurality of rooms, a public washroom and a corridor, a negative pressure area is formed in the public washroom after airflow organization design, a 15mm high door slot is formed in a lower opening of a door of each room, and the corridor forms a corridor air return area. A heat recovery fresh air ventilator is installed in the public washroom, fresh air is conveyed into all rooms through the heat recovery fresh air ventilator, return air in the rooms is recovered into the heat recovery fresh air ventilator after passing through a corridor air return area from high door cracks of the rooms, and the return air exchanges heat with the fresh air in the heat recovery fresh air ventilator and then is discharged outdoors. The fresh air system exchanges air in the public washroom in real time, the ventilation capacity of the public washroom is met, the comfort level of the public washroom is improved, the design requirement