Radiator Reflective Thermal Insulation Foam Backed Foil 4m x 47cm Thermall energy saving Radiator Heat Reflector offer buyers the added benefit of foam backed foil for greater heat reflection radiators located on an external wall can lose up to 30% of their heat by warming the wall which simply goes outside. Installing specially-treated radiator foil can prevent this as the heat is reflected back into the room. It only takes minutes to fit! Simply measure your radiator, cut the roll to size, apply double sided sticky tape to the rear of the foil and attach to the wall behind the radiator.