Both, the outside and the inside of the sandwich panel are made of metal. The most commonly used are steel and aluminum and used for thermal insulation (eg expanded polystyrene "EPS" or glass wool "MW") (EN 14509). The basic idea of the Interreg project "ABS-Network SIAT 125" is the activation of a conventional sandwich panel with solar energy.  Thermal activation in this case means the conversion of sunlight, which provides energy, into thermal energy for the treatment of hot water and / or for heating and cooling.