The regulations for Passivhäuser (or houses with the respective efficiency rating) in fact require a ventilation system with heat recovery (since the otherwise

The regulations for Passivhäuser (or houses with the respective efficiency rating) in fact require a ventilation system with heat recovery (since the otherwise necessary open-the-windows-like-a-savage-system wastes too much energy). These nowadays come typically with moisture recovery (which arguably not always works well enough, depends on how much you still need to heat).