Building regulations are currently under development across Europe in advance of the implementation of the nearly Zero Energy Buildings (nZEB) standard at national member state level. However, when revising the national building regulations to improve energy efficiency, few examples exist of the monitored performance of such dwellings, making informed decision-making difficult. This paper reports on the monitored performance of nZEB compliant dwellings which were built to the Passive House (PH) Standard. It finds that the PH bedroom CO2 concentrations are significantly better than in houses built to the current building regulations which use natural ventilation.