Is there a minimum spacing that should be followed when installing a new supply line into a room? I'm remodeling my basement and have two supply vents in the ceiling, but wanted to add 1 or 2 near the floor. For logistical reasons the only wall I can do that on is where the cold air return sits. Without knowing much about hvac, my assumption is that hot air being blown in would get sucked right into the cold air return since the register would be about 3' away from the cold air return. Or is this assumption wrong, and it'd be ok to do it?