Heat exchange system for use in a building ventilation system, comprising a housing which contains: a first flow passage having a first main air connection at one end of the first flow passage, at the other end of which first flow passage a first secondary air connection is located, a first booster for ensuring the flow of air through the first secondary air connection via the first flow passage and the first main air connection, a second flow passage having a second main air connection at one end of the second flow passage, at the other end of which second flow passage a second secondary air connection is located, a second booster for ensuring the flow of air via the second main air connection, the second flow passage and the second secondary air connection, and a heat exchanger by means of which at least a first main branch of the first flow passage and at least a second main branch of the second flow passage are in a heat-exchanging relationship to each other, wherein the first flow passage further comprises a first bypass branch which is adapted to bypass the heat exchanger, and a first bypass flow regulator which is located in the first bypass branch, wherein the second flow passage further comprises a second bypass branch which is adapted to bypass the heat exchanger, and a second bypass flow regulator which is located in the second bypass branch, characterized in, that the housing is provided with a control unit adapted to control the first bypass flow regulator in order to regulate the flow of air through the first bypass branch and/or to control the second bypass flow regulator in order to regulate the flow of air through the second bypass branch, that the control unit is adapted to control the first and/or second bypass flow regulator on the basis of a configurational setting associated with a left-handed system in which a connection on the left side is adapted to provide supply air during use or a right-handed system in which a connection on the right side is adapted to provide supply air during use, and that said configurational setting is adjustable on the basis of a user input signal. a first flow passage having a first main air connection at one end of the first flow passage, at the other end of which first flow passage a first secondary air connection is located, a first booster for ensuring the flow of air through the first secondary air connection via the first flow passage and the first main air connection, a second flow passage having a second main air connection at one end of the second flow passage, at the other end of which second flow passage a second secondary air connection is located, a second booster for ensuring the flow of air via the second main air connection, the second flow passage and the second secondary air connection, and a heat exchanger by means of which at least a first main branch of the first flow passage and at least a second main branch of the second flow passage are in a heat-exchanging relationship to each other, wherein the first flow passage further comprises a first bypass branch which is adapted to bypass the heat exchanger, and a first bypass flow regulator which is located in the first bypass branch, wherein the second flow passage further comprises a second bypass branch which is adapted to bypass the heat exchanger, and a second bypass flow regulator which is located in the second bypass branch, wherein the first flow passage further comprises a first bypass branch which is adapted to bypass the heat exchanger, and a first bypass flow regulator which is located in the first bypass branch, wherein the second flow passage further comprises a second bypass branch which is adapted to bypass the heat exchanger, and a second bypass flow regulator which is located in the second bypass branch, characterized in, that the housing is provided with a control unit adapted to control the first bypass flow regulator in order to regulate the flow of air through the first bypass branch and/or to control the second bypass flow regulator in order to regulate the flow of air through the second bypass branch, that the control unit is adapted to control the first and/or second bypass flow regulator on the basis of a configurational setting associated with a left-handed system in which a connection on the left side is adapted to provide supply air during use or a right-handed system in which a connection on the right side is adapted to provide supply air during use, and that said configurational setting is adjustable on the basis of a user input signal.