When connecting multiple vents, which should be at the bottom?

The largest vent should be positioned at the bottom when connecting multiple vents. This is primarily due to the principle of air dynamics: larger ducts have a greater capacity to handle larger volumes of air. By placing the largest vent at the bottom, it allows for efficient airflow distribution, as the heavier and larger volume of warmer air tends to rise.

Additionally, this configuration minimizes turbulence and resistance, providing a more balanced air distribution throughout the system. It ensures that the airflow is optimized, allowing smaller vents higher in the system to effectively draw from the larger vent below, thus enhancing the overall efficiency and effectiveness of the HVAC system. This best practice facilitates improved comfort levels and energy use within the environment being conditioned.