The second floor of my house consists of three bedrooms and a bathroom all of which are off of a hallway at the top of the stairs. All the rooms have one hvac vent, and one air return. The problem is the hallway, which has no vent and is a large space because about halfway up the stairway, it opens up all the way to the upstairs ceiling. This creates a dead space which never really cools in the summer and never really heats up in the winter. Anybody have any suggestions for fixing this, besides expensive duct work rerouting?