Technikakzeptanz im Niedrigenergiehaus Acceptation of technical equipment in low energy houses

Continuous measurements have been operated on 28 identical low energy houses near Leipzig (Germany) during two years.The houses face due south, have two levels and one occupied attic, with a total aera of 147 m2. Heating period is from September to May. All houses except 2 were equipped with different mechanical ventilation systems, providing about 180 m3/hr of fresh air : central balanced flue systems with heat recovery, air heating system with heat recovery, central exhaust ventilation with heat recovery by heat pump, room mechanical ventilation systems. Two houses were equipped with natural ventilation openings in windows.Measurement results show no correlation between the duration of windows openings by inhabitants in winter (which varies in a ratio from 1 to 26) and the type of ventilation system. Windows opening time tends to decrease when the outside temperature is lower.The mean values of final energy consumptions are about 60 to 65 kWh/m2/year for all ventilation system types, with a large interval of individual values (e.g. from 43 to 112 for the 13 houses with central balanced flue systems with heat recovery). Results also show that indoor air quality (CO2 and VOC concentrations) is better when ventilation system is in operation and/or windows are opened. No negative effect of ventilation systems has been noted concerning airborne bacteria and spores ; their concentration has been found being lower in fresh air supplied by ventilation system than outdoors.