Ventilation climate system for regulating a climate in a room of a building, in particular a residential building, comprising: - a return air system for guiding a flow of return air, comprising a return air inlet for taking in return air from the room, a return air outlet arranged outside of the room for expelling return air from the return air system; - a supply air system for guiding a flow of supply air, comprising a supply air inlet for taking in supply air from outside the room, a supply air outlet for supplying supply air into the room; - a heat exchange system arranged between the return and supply air systems for exchanging heat between the flow of return air and the flow of supply air; - a temperature adjustment unit comprising a heat transfer member for adjusting the temperature of the flow of supply air, wherein the heat transfer member is arranged in the supply air system between the supply air inlet and the supply air outlet and downstream of the heat exchange system , wherein the temperature adjustment unit comprises a heat pump comprising an interior unit and an exterior unit, wherein heat transfer member comprises the interior unit, characterized in that the exterior unit is arranged inside, or coupled to, an air mixing unit that is arranged for taking in air from outside the room, wherein the return air outlet is coupled to the air mixing unit and wherein the air mixing unit is arranged for mixing the expelled return air and the air from outside the room, wherein the air mixing unit is comprised in a roof mounted cover , wherein the air mixing unit is formed as an air mixing chamber comprising at least a first air mixing chamber inlet that is connected to the return air outlet , a second air mixing chamber inlet that is arranged for taking in fresh outdoor air, and an air mixing chamber outlet for expelling mixed air from the air mixing chamber. - a return air system for guiding a flow of return air, comprising a return air inlet for taking in return air from the room, a return air outlet arranged outside of the room for expelling return air from the return air system; - a supply air system for guiding a flow of supply air, comprising a supply air inlet for taking in supply air from outside the room, a supply air outlet for supplying supply air into the room; - a heat exchange system arranged between the return and supply air systems for exchanging heat between the flow of return air and the flow of supply air; - a temperature adjustment unit comprising a heat transfer member for adjusting the temperature of the flow of supply air, wherein the heat transfer member is arranged in the supply air system between the supply air inlet and the supply air outlet and downstream of the heat exchange system , wherein the temperature adjustment unit comprises a heat pump comprising an interior unit and an exterior unit, wherein heat transfer member comprises the interior unit, the exterior unit is arranged inside, or coupled to, an air mixing unit that is arranged for taking in air from outside the room, wherein the return air outlet is coupled to the air mixing unit and wherein the air mixing unit is arranged for mixing the expelled return air and the air from outside the room, wherein the air mixing unit is comprised in a roof mounted cover , wherein the air mixing unit is formed as an air mixing chamber comprising at least a first air mixing chamber inlet that is connected to the return air outlet , a second air mixing chamber inlet that is arranged for taking in fresh outdoor air, and an air mixing chamber outlet for expelling mixed air from the air mixing chamber. <EOS>