Question: Is having a branch off the end of main heating HVAC duct bad and if so, why?
Background: A heating and cooling contractor sales representative came to my home today. He saw the situation pictured below and said that having a branch off of the end of the main heating duct is bad because it does not allow the main branch to maintain pressure.
I presently fail to see how a branch off the end compared to the same sized branch off the sides (recommended by the sales representative) of the HVAC would make any difference in the performance of the system. I would like to understand the physics behind why this is bad before I pay to have it corrected.