The invention relates to a vented laundry dryer, comprising an air inlet duct, an air outlet duct, a heat recovery system for transferring heat from the air outlet duct to the air inlet duct, and an additional heater, wherein the heat recovery system is a heat pump comprising an evaporator, a liquefier, a condenser, and a relaxation unit, wherein the liquefier is thermally coupled to the air inlet duct, and the evaporator is thermally coupled to the air outlet duct, and a relaxation property of the relaxation unit can be adjusted depending on at least one parameter that is connected to an activity of the additional heater. A method is used to operate a vented heat dryer comprising an additional heater and a heat pump having a relaxation unit, wherein the method comprises the following steps: (a) monitoring at least one parameter that is connected to an activity of the additional heater; and (b) changing a relaxation property of the relaxation unit depending on the at least one parameter.