## 2 Materials and Methods
### Experimental Layout-Thermal Testing  
The European Committee for Standardization (CEN) and the International Organization for Standardization (ISO) propose detailed standards for testing and designing water heating and cooling panels both for floor and ceiling applications [23; 24; 25]. In this work, a commercial standalone electric radiant heating panel has been tested with the aim of being able to evaluate the performance in a controlled space. For this purpose, the climatic room of the Institute for Construction Technologies in Padova (Italy) has been utilized. The room is placed inside a building, and it is constituted by a thermally insulated chamber made of panels with a thickness of 5 cm and thermal conductivity of 0.04 W m\({}^{-1}\) K\({}^{-1}\). The internal dimensions are equal to 4.36 m \(\times\) 8.42 m \(\times\) 3.45 m: the floor surface is therefore equal to 36.71 m\({}^{2}\), and the total volume is equal to 126.5 m\({}^{3}\). The room is completely surrounded by an empty cavity in which air flows with a maximum flow rate value equal to 7000 m\({}^{3}\) h\({}^{-1}\): the air temperature is controlled by an air treatment unit. The air temperature in the cavity allows for the control of the conditions of the surface temperature of the test room. The air temperature inside the cavity is controlled in a continuous way around the setpoint to maintain a very stable internal operating temperature during the measurements: the distribution of surface temperature is in the range of \(\pm\)0.3 \({}^{\circ}\)C. The air treatment unit is connected to a reversible heat pump that provides heating and cooling. The heat pump is a Carrier 30 RH 005 model, 5.1 kW nominal cooling capacity, 5.7 kW nominal heating capacity, 2.02 kW power consumption for cooling, and 2.09 kW power consumption for heating. Inside the climatic test room, an insulated chamber was installed above the existing floor. The new room was built with sandwich panels of expanded foam (polyurethane) and fiberglass-reinforced epoxy resin, white painted with medium-high emissivity varnish (0.75 in the long wave infrared band) on both inner and outer side. The polyurethane foam layer has a thickness of 70 mm and a thermal conductivity of 0.023 W m\({}^{-1}\) K\({}^{-1}\); the thermal transmittance is equal to 0.33 W m\({}^{-1}\) K\({}^{-1}\). The external dimensions of the room are equal to 3.34 m \(\times\) 4.41 m \(\times\) 3.15 m. The dimensions are therefore compatible with those provided by the standard UNI EN 14240 [25] for the test of radiant ceiling systems. Inside the chamber a water-radiant ceiling was installed, made by 6 modules connected in three parallel series of 2 modules each. The inlet and outlet pipes are connected to a system placed outside the cell, which delivers either hot or cold water. The maintenance of the operating conditions and their measurement are obtained with a network of sensors and actuators and controlled by a real time system. This system is supervised by a computer through the internet network. The control and measurement software was developed in LabView platform. All the temperature sensors have been calibrated in the laboratory, while the flow sensors were verified after the installation of the electric radiant panel. Table 2 summarizes the type and number of sensors utilized in the hot/cold water generation system. Table 3 describes the sensors utilized inside and outside the test chamber.