Can I have an open fireplace in a Passive House?

The answer from an Australian perspective is very likely to be no. Having an open fireplace would introduce too much heat into the space and may dramatically reduce the efficiency of the mechanical heat recovery ventilation system (due to lack of airtightness). However, there are other really clever means of having a real flame effect in your Passive House, including bio-ethanol fires as well as wood burning boilers or stoves with glass fronts. By the way, if you have young children in the house, please reassure them that Santa Claus knows Passive House Buildings very well and he uses the ventilation system and some magic dust to bring the gifts for Christmas morning.