What could be causing steam on the inside, front windshield?

There was no antifreeze in the reserve & the car over heated. Almost 2 gallons of water was put in the reserve & the car ran fine for a couple hours. The temperature gauge was normal & no indicator lights came on but while driving, steam started coming from the vents onto the windshield! Tried turning the heater & air conditioner, didn't help. There was no water on the floor or passenger compartment. It has a new radiator! It also has a cracked head gasket!