Return air vents aren't required in every room, but proper placement is essential for system efficiency. According to industry standards, you'll need one return vent for every 100 to 150 square feet of living space. Ideally, each room would have its own return vent, especially larger rooms exceeding 100 square feet.
Without adequate return airflow, your HVAC system works harder, energy costs increase, and comfort decreases. A professional assessment can determine the optimal number and placement of return vents for your specific home layout.