What is the difference between a hot and a cold air register?

Hot air registers are referred to as the supply. This is where the warm air comes out of your furnace to heat your home. The cold air registers are referred to as “the return.” This is where the air enters the air duct system and is drawn towards the blower fan, which sends the air back through the supply. The hot air register is where the warm air comes from the furnace and circulates through your home. The cold air return is where the air from your home enters the air duct system and is drawn towards the furnace to be heated or cooled. By circulating the air through the home, it helps to even out the temperature and create a comfortable environment.