Some common design considerations for VAV systems in commercial buildings include duct sizing and layout, terminal unit selection, and control strategy. Duct sizing and layout must be carefully planned to ensure that airflow is delivered consistently to all zones, while minimizing pressure drops and energy losses. Terminal unit selection depends on factors such as zone size, load, and occupancy patterns. Control strategy involves selecting the appropriate control algorithms and sensors to ensure that the VAV system operates efficiently and effectively, while maintaining a comfortable indoor environment.