Hi, Noel,

Heating and cooling loads in a home vary from room to room due to a number of factors including room size, insulation levels, solar orientation, the area of windows, exterior doors, the area of exterior walls, air infiltration, the number of occupants, heat-generating appliances such as computers, and, well, you get the point.

BR 4 is the only bedroom in your home with two exterior walls (assuming your garage isn't air conditioned or heated.) So there is both more heat transfer from the exterior and more potential for infiltration of hot, humid outdoor air. As a consequence, the amount of cooling required to maintain comfortable conditions in BR 4 will be greater than other bedrooms of similar area which have less exterior wall area. I suspect BR 4 is set up with the same air flow rate as the other, similar-sized bedrooms. That can be corrected by balancing the air flows to the rooms. Your duct work should be equipped with balancing dampers for this purpose. If not, balancing dampers can be installed on a retrofit basis.