Central Fresh-Air Systems Cannot Independently Control Every Room's Airflow and Temperature

However, it also has a drawback: the fresh-air volume and fresh-air temperature in individual rooms cannot be controlled independently.

Many consumers overlook this important issue. Family members have different needs: some prefer cool air at 17-22 degrees C while sleeping, while others are easily awakened by the cold. Some prefer warmth during the day and cooler conditions at night. One room may be temporarily empty, another may host many guests for a short time, and a baby may be sleeping in the nursery. In all these situations, the fresh-air volume and supply-air temperature should be controlled independently for each room.

A central fresh-air system, by contrast, can only deliver the same fresh-air volume evenly to all rooms, switching them all on and off together.