Device, comprising: - a heat exchanger which is at least partially enclosed by an insulating material; - wherein the insulating material comprises a vacuum-packed core material; - wherein the heat exchanger is received in a housing with a number of walls (2, 3), wherein the vacuum-packed core material is arranged between at least one of the walls (2, 3) and the heat exchanger; - wherein the vacuum-packed core material is embodied as a panel, and such a vacuum panel is arranged along at least one of the walls; characterized in that - the device is a heating device configured to heat a flowing medium such as water, further comprising a heating module which is at least partially enclosed by an insulating material; - wherein the heating device is configured to heat the flowing medium used to heat a space or suitable for heating tap water using heat from the heating module; - wherein the vacuum-packed core material is arranged at a distance from both the heating module and the heat exchanger; - wherein the heating module is received in the housing with the number of walls (2, 3), wherein the vacuum-packed core material is arranged between at least one of the walls (2, 3) and the heating module; - wherein at least one spacer (5, 6, 9, 15) arranged between the heating module and the heat exchanger on the one side and the at least one vacuum panel on the other side to maintain the distance; - wherein the heating module and/or the heat exchanger is fixed with bolts to the wall of the housing; and - wherein the vacuum panel fits within the bolts, enclosing vacuum panel between wall and spacer (5, 6, 9, 15). - a heat exchanger which is at least partially enclosed by an insulating material; - wherein the insulating material comprises a vacuum-packed core material; - wherein the heat exchanger is received in a housing with a number of walls (2, 3), wherein the vacuum-packed core material is arranged between at least one of the walls (2, 3) and the heat exchanger; - wherein the vacuum-packed core material is embodied as a panel, and such a vacuum panel is arranged along at least one of the walls; - the device is a heating device configured to heat a flowing medium such as water, further comprising a heating module which is at least partially enclosed by an insulating material; - wherein the heating device is configured to heat the flowing medium used to heat a space or suitable for heating tap water using heat from the heating module; - wherein the vacuum-packed core material is arranged at a distance from both the heating module and the heat exchanger; - wherein the heating module is received in the housing with the number of walls (2, 3), wherein the vacuum-packed core material is arranged between at least one of the walls (2, 3) and the heating module; - wherein at least one spacer (5, 6, 9, 15) arranged between the heating module and the heat exchanger on the one side and the at least one vacuum panel on the other side to maintain the distance; - wherein the heating module and/or the heat exchanger is fixed with bolts to the wall of the housing; and - wherein the vacuum panel fits within the bolts, enclosing vacuum panel between wall and spacer (5, 6, 9, 15).