Here, we analyze the impact of ventilation heat recovery (VHR) on the operationprimary energy use of a case-study timber-frame building using different heatsupply systems including electric resistance heating, bedrock heat pump and districtheating based on combined heat and power (CHP) production. We model theprimary energy use for the original and improved level of energy efficiency of thebuilding, both with and without VHR. VHR increases the electrical energy used forventilation and reduces the heat energy used for space heating. Significant primaryenergy savings is achieved when VHR is used in electric resistance heatedbuildings than in district heated buildings. For district heated buildings the primaryenergy savings are small. VHR systems can give substantial final energy reduction,but the primary energy benefit depends strongly on the type of heatsupply system, and also on the amount of electricity used for VHR and the airtightnessof buildings. This study shows the importance of considering the interactionsbetween heat supply systems and VHR systems to reduce primary energyuse in buildings.