Air supply registers may be located in floors or walls?

AIr supply registers can be located in the floors, walls, or ceilings. The placement chosen will depend on whether the system will be used primarily for heating or cooling. If you live in an area where you use mostly heating, floor registers are the best, as heat will rise and mix with the indoor air. If you live in a warm area, like me, you want the registers high on the walls or on the roof, as the cold supply air will fall towards the floor. Basically you want high registers for cooling and low registers for heating.