A study or work zone can be considered independently when its occupancy and equipment loads differ from the rest of the house. The final zoning plan must maintain system balance.

Large glazing can materially change heating and cooling demand. Orientation, shading and glass performance are included in the assessment before capacity is recommended.

Possibly through an appropriate upgrade pathway, but only after inspection. Condition, sizing, leakage, routing and compatibility determine whether reuse is sensible.

Appropriate zoning can limit service to unoccupied areas, subject to the system maintaining required airflow. Energy use still depends on set points, weather, building fabric and the way occupants operate the system.

That may work where bedroom loads and schedules are similar. Rooms with different orientations, glazing or use may need another arrangement, which is why the plan is checked room by room.