Performances of ventilation systems can fall off because of wind pressure and pressure drops of frosted heat-exchange units. Though performance stability is necessary to maintain indoor air quality and energy saving, evaluation methods of its stability haven't be defined. In this paper, firstly, the calculation methods of airflow and ventilation load in consideration of changes of P-Q curve of a fan and pressure loss among the airflow path is described. Secondly, characteristics of the change in responses to frost and wind pressure are measured. Then, to estimate parameters of airflow and ventilation load calculation referring the above measured characteristics data is tried.
