Can you open windows in a passive house?
Of course, occupants may open windows whenever they want; however, they won’t have to. A passive house is continuously supplied with fresh air via the ventilating system. This has advantages: Unlike window ventilation, fine filters in the ventilating system keep out dirt and pollen. Air quality within the house is always excellent, even when occupants are away and/or windows are never opened. Of course, as with all houses, if windows are left open in winter for longer periods, the inside air temperature will decrease noticeably, and energy consumption for heating will increase.
People often express reservations about the need for a ventilation system: are there problems with bacteria, noise and drafts?
The ventilation system in a passive house is a fresh air supply system, not an air conditioning system that recirculates inside air. Bacteria growth is only a problem in recirculating air systems (and then, only if poorly maintained). Fan and valve noises are almost completely eliminated by sound control measures (e.g., vibration isolation mounts, low air speed, acoustic lining in ducts). Jet nozzles guide incoming air along the ceiling from where it uniformly diffuses throughout the room at velocities that are barely perceptible.
Read how other myths about passive houses are being dispelled.