... fiberglass layer + 25mm high- density fiberglass board. Minimum the heat lossBack sheet: embossed aluminum plate 0.5mm / gavanized steel board ... -temperature resistance 5, corrossive-resistance, no scaling 6, high heat transfer speed 7, high conductivity 8, pressure standing 9, ... ,Eastern Europe ,Southeast Asia, Mid East ,Western Europe. CE, Solar Keymark split flat plate solar water heater collector