Stability of mechanical exhaust systems.

The mechanical exhaust system, where outdoor air is supplied through infiltration and devices in the building shell, is a common ventilation technique in multi-family buildings in Europe. The objective of this paper is to determine how well the system meets indoor air quality standards and regulations and how sensitive it is to disturbances, such as window opening, temperature differences and resident behavior, and how different building construction parameters affect the airflow. A simple model of a multi-family building has been simulated with a multi-zone infiltration program. It was found that the system almost never fulfills the regulations and that the actions of one resident can often affect the airflow in other apartments. The use of standards and regulations defining indoor air quality and energy efficiency will be ineffective for these systems because they are not stable, that is, sensitive to disturbances such as weather changes and resident behavior.