Yes, the ventilation system inside a passive house needs not only a heat exchanger, but a humidifier as well. Actually, I'd rather dry my laundry to humidify the room than rely on a humidifier that can grow bacteria and mold inside.
> [...] than rely on a humidifier that can grow bacteria and mold inside.
That's down to maintenance and care; change the filters and clean it regularly. Like everything else in your house. You need to change and maintain filters in a heat exchanger as well.
