I have a dedicated HVAC unit for the rooms on the second floor of my house. A bedroom at the opposite side to where the HVAC unit sits doesn't get enough AC or heat. Right now, in winter, that room could be 10 degrees cooler than other bedrooms on the same level. I confirmed the vents are open in the room. It seems not enough hot air is reaching that room. What could be the problem?
There's a supply vent that seems to disproportionately and needlessly heating the hallway and top of the stairwell. I tried to close the vent but that didn't improve the situation in the cold bedroom.