Is it unhealthy to occupy an ‘air-tight’ building?

It is probably truer to say it is more unhealthy living in a draftee space typical of Australian buildings. One of the main benefits of Passive House buildings are the high air quality as a direct result of air-tight design that allows the controlled provision of lots of fresh air via a balanced ventilation system. In normal buildings, fresh air enters the building through a series of vents and through infiltration or drafts. However, such means of ventilation is uncontrolled and you cannot be sure that all spaces at all times are being properly or sufficiently supplied with the correct amount of fresh air. Indeed, as the entire volume of air in a typical Passive House is changed on average between 8 to 12 times per day (depending on the setting of the system) ensuring very high air quality throughout, plant growth is known to flourish, a sure sign that things the space is healthy!