An air conditioning and ventilating system for a two-story building with a water tank disposed on the roof includes a first condenser unit and a first air handling unit for cooling a first set of primary cooled rooms and a first set of secondarily cooled rooms on an upper floor of the building. The system also includes a second condenser unit and a second air handling unit for cooling a second set of primarily cooled rooms and a second set of secondarily rooms on a lower floor and wherein the second condenser unit and second air handling unit are independent of the first condenser unit and first air handling unit. On both floors cool air from the first set of rooms is partially returned to the air handling units and partially recirculated into the primary cooled rooms.