Building having at least one panel heater for at least one room in the building, - wherein the respective panel heater is equipped with multiple heating circuits, each of which has a flow line and a return line, - wherein the respective heating circuit is connected via its flow line to a supply line to which multiple heating circuits are connected, and is connected via its return line to a discharge line to which multiple heating circuits are connected, - wherein a separate connection box is provided for each heating circuit, which box is mounted in the room or room section to be heated by the heating circuit and has a return coupling in a box interior, - wherein the connection box has a housing containing the box interior, - wherein in the box interior the return line is connected to the return coupling via a return connection formed on the return coupling and the discharge line is connected to the return coupling via a discharge connection formed on the return coupling, - wherein exactly four lines are connected to the respective connection box, namely the supply line, the discharge line, the flow line and the return line, - wherein a first control valve is provided which is coupled to a thermostatic head to control the temperature of the room or room section to be heated, which thermostatic head is arranged on an outer side of the connection box exposed to the room or room section to be heated, characterised in that - the connection box also has a flow coupling in the box interior, - in the box interior, the supply line is connected to the flow coupling via a supply connection formed on the flow coupling and the flow line is connected to the flow coupling via a flow connection formed on the flow coupling, - the first control valve is installed in a receptacle formed on the flow coupling, - a shut-off valve is provided with which the fluidic connection between the return line and the discharge line can be shut off to deactivate the heating circuit, - the shut-off valve is installed in a receptacle formed on the return coupling, - the flow coupling and the return coupling are fastened separately to the housing by means of fastening elements, - the supply connection, the flow connection, the discharge connection and the return connection are parallel to each other and oriented vertically downwards, - the flow line, the return line, the supply line and the discharge line run parallel to each other and vertically in a connection section adjacent to the connection box. - wherein the respective panel heater is equipped with multiple heating circuits, each of which has a flow line and a return line, - wherein the respective heating circuit is connected via its flow line to a supply line to which multiple heating circuits are connected, and is connected via its return line to a discharge line to which multiple heating circuits are connected, - wherein a separate connection box is provided for each heating circuit, which box is mounted in the room or room section to be heated by the heating circuit and has a return coupling in a box interior, - wherein the connection box has a housing containing the box interior, - wherein in the box interior the return line is connected to the return coupling via a return connection formed on the return coupling and the discharge line is connected to the return coupling via a discharge connection formed on the return coupling, - wherein exactly four lines are connected to the respective connection box, namely the supply line, the discharge line, the flow line and the return line, - wherein a first control valve is provided which is coupled to a thermostatic head to control the temperature of the room or room section to be heated, which thermostatic head is arranged on an outer side of the connection box exposed to the room or room section to be heated, - the connection box also has a flow coupling in the box interior, - in the box interior, the supply line is connected to the flow coupling via a supply connection formed on the flow coupling and the flow line is connected to the flow coupling via a flow connection formed on the flow coupling, - the first control valve is installed in a receptacle formed on the flow coupling, - a shut-off valve is provided with which the fluidic connection between the return line and the discharge line can be shut off to deactivate the heating circuit, - the shut-off valve is installed in a receptacle formed on the return coupling, - the flow coupling and the return coupling are fastened separately to the housing by means of fastening elements, - the supply connection, the flow connection, the discharge connection and the return connection are parallel to each other and oriented vertically downwards, - the flow line, the return line, the supply line and the discharge line run parallel to each other and vertically in a connection section adjacent to the connection box.