Flat insulating panel in rolls of expanded polystyrene (EPS) or extruded polystyrene (XPS), coupled with a reflective aluminum-colored raffia (HDPE) film, with a printed on pattern useful for pipe laying (50 x 50 mm installation grid). The tear resistant film facilitates the fixing of the piping using clips with the “tacker” system and protects the insulation from the humidity of the screed during construction phases; it also acts as a vapor barrier in the operating phase of the radiant system. The film is equipped with a self-adhesive strip on one side, to ensure the connection and the overlap between adjacent panels, ensuring an optimal seal during the laying of the rolls and the casting of the screed.