Arrived on site to address some airflow imbalanced upstairs. There is a specific room that is very cold in the winter and warm in the summer. We looked through the equipment, layout, and design to get a holistic interpretation of what may be the cause. They did explain that this has been an occurrence for about a decade, when they bought the house. We did find duct work connected and unobstructed without kinks or any major concerns. The upstairs hallway is very warm due to it being open to the entry and the downstairs, there is no return near the entry and heat gets trapped at the top of the staircase. Also in that hallway is the water heater which is radiating more heat than expected. The room in question almost always has the door closed and is the furthest from the thermostat also. We did feel a draft coming from the window with failed seals and the condensation in the windows indicated some insulation failures in the window. All this containing to the temperature discrepancy. We sp