Can I still open windows in a Passive House?

Windows can be opened in Passive Houses but in practice most occupants choose to keep them closed in the cold months of the year as continuous fresh air is provided by a mechanical ventilation with heat recovery (MVHR) system. Upon moving into a house with an MVHR system, it usually takes a few weeks to get used to the new situation, that high comfort levels and excellent air quality are maintained even with closed windows. In summer, opening windows at night will help keep the house cool but in winter doing so may increase fuel costs for the resident as heat will be needed to warm the house back up again.

Unlike air conditioning systems, which can only operate efficiently with closed windows, a MVHR system is not disturbed by the opening of windows. E.g. in summer or when there are lots of guests in the house, feel free to open your windows or patio doors.