The performance of the ventilation system is considered an integral element of the primary Passivhaus heating demand calculation, though the rest of the services are not. You can think of this as being because the main intake and exhaust ducts, carrying cold air, actually form part of the building’s external envelope. So in keeping with the emphasis on compact form, the designer needs to be aware of these ducts and how to make them as short as possible at an early stage in design.
The impetus for using MVHR may have come from the opportunity for heat recovery but now we recognise that the main benefi t of these ventilation systems is basically good ventilation. The Passivhaus standard sets detailed criteria for airflow rates, noise levels and commissioning which, if followed, will lead to ventilation that works well. The ventilation section of this guide provides specific details about designing ventilation to the Passivhaus standard.