Use of mechanical ventilation in Finnish houses

This study reports ventilation measurement and occupant questionnaire results from newly built 102 Finnish detached houses. The results show that ventilation units were used constantly and the fan speed setting was changed very seldom. There was as light tendency to use higher speed in the summer than in winter. Ventilation units provide an average actual air change rate of about 0.4 ach (13 L/s,pers) both in winter and summer which is less than the code value of 0.5 ach. Airflow measurements at design fan speed show that only 57% of houses comply with regulations. Low actual air change rates were caused by low fan speeds used by occupants as 52% of houses in the winter and 47% in the summer used the lowest possible fan speed. Correspondingly, actual supply airflow rates in bedrooms were low, in average 4 L/s. Occupant complaints about ventilation noise correlated with noise level in bedrooms. It is concluded that ventilation noise is an important factor affecting the use of ventilation units. Inspection of drawings and ventilation systems showed that in houses not complying with ventilation regulations either ventilation units were undersized or sound attenuation was poor.