The passive house standard of northern European countries functions as an inspiration for home owners and project developers for building or retrofitting with high energy ambitions. Passive houses typically involve high insulation levels and heat recovery ventilation. Residual heating is based on heating of the inlet airflow, but other solutions (stove etc.) are applied as well. The development of energy-efficient building is technology driven. The feedback from the consumers is low and there have been complaints by occupants about perceived health effects of heat recovery ventilation. Examples of passive houses are analyzed to find indicators of "emerging" health risks. Potential problems are overheating, noise from installations, legionella contamination of domestic water buffers, low ventilation volumes, complex control mechanisms and lack of flexibility of ventilation services. Recommendations are given for the improvement of the user friendliness of indoor climate systems for passive houses.