Controlled ventilation systems help to increase comfort and ensure hygienically satisfactory indoor air. In addition, heat recovery via a heat exchanger can save energy.

The following criteria are prerequisites for a ventilation system appropriate to passive houses:

• Heat recovery rate η_WRG,eff ≥ 75 %
• Intake air temperature > 16.5 °C to ensure comfort
• Electrical efficiency pel < 0.45 Wh/m³
• Ventilation system largely leak-free
• Noise level in living space < 25 dB(A)