A heating, ventilation, and air-conditioning (HVAC) system includes a blower, a fresh-air valve, a bypass duct, and a bypass valve. The blower is configured to urge air to flow from an inlet to an outlet of the blower. The fresh-air valve is operable to provide a mixture of air drawn from an outside-air duct and a recirculated-air duct to the inlet. The fresh-air valve is operable to a recirculate position where the outside-air duct is substantially blocked from communicating with the inlet. The bypass duct is configured to couple the outlet to the outside-air duct. The bypass valve is located in the bypass duct and is operable to a closed position and an open position. The cabin is ventilated when the fresh-air valve is in the recirculate position, the bypass valve is in the open position, and the blower is operated to blow air out of the outside-air duct.