If a building is heated by a heat pump, it is of high importance that the heat pump has a high coefficient of performance. An exhaust air heat pump extracts heat from the building’s exhaust air. The air has a relatively high and constant temperature all year around, leading to a high seasonal coefficient of performance. This thesis examines whether it is profitable to complement an exhaust ventilation system with an exhaust air heat pump in an apartment block that already has geothermal heat pump, district heating, oil- or biofuel heated system. To determinate the profitability, a reference building in Strömstad has been used and was considered a representative of Sweden’s other apartment blocks. The result of the study indicated that it is economically justifiable to combine an exhaust air heat pump with district heating, oil- and biofuel heated system. However it must be added that exhaust air heat pumps are best suited for single-family houses since they provide relatively low energy compared to e.g. geothermal heat pumps.