A method for producing an insulating element for the production of frame parts, the method comprising the following steps: a) providing an at least two-part openable and closable molding tool having at least one first mold part and one second mold part, said mold parts, in the closed state of the molding tool, forming a cavity and representing the three-dimensional outer shape of the insulating element, the mold parts being connected to each other in the closed state of the molding tool and at least partially separated from each other in the opened state of the molding tool; b) disposing at least one sheet-like reinforcing element at the first mold part and at least one sheet-like reinforcing element at the second mold part, in the closed state of the molding tool, the sheet-like reinforcing elements being located in the cavity formed by the mold parts; c) introducing a flowable, curable plastic mass into the cavity formed by the mold parts of the molding tool; d) allowing the plastic mass to harden in the molding tool; e) opening the molding tool and removing the insulating element formed in such a manner; f) disposing spacers at the insulating element; g) inserting the insulating element into an openable and closeable foaming tool, the entire surface of the insulating element being kept at a distance from mold surfaces of the foaming tool by the spacers projecting from said insulating element; h) surrounding the insulating element in the closed foaming tool with a curable plastic mass; i) allowing the plastic mass to cure in the foaming tool; j) opening the foaming tool and removing the now sheathed insulating element, characterized in that the curable plastic mass is an essentially UV stable plastic mass containing at least one dye. a) providing an at least two-part openable and closable molding tool having at least one first mold part and one second mold part, said mold parts, in the closed state of the molding tool, forming a cavity and representing the three-dimensional outer shape of the insulating element, the mold parts being connected to each other in the closed state of the molding tool and at least partially separated from each other in the opened state of the molding tool; b) disposing at least one sheet-like reinforcing element at the first mold part and at least one sheet-like reinforcing element at the second mold part, in the closed state of the molding tool, the sheet-like reinforcing elements being located in the cavity formed by the mold parts; c) introducing a flowable, curable plastic mass into the cavity formed by the mold parts of the molding tool; d) allowing the plastic mass to harden in the molding tool; e) opening the molding tool and removing the insulating element formed in such a manner; f) disposing spacers at the insulating element; g) inserting the insulating element into an openable and closeable foaming tool, the entire surface of the insulating element being kept at a distance from mold surfaces of the foaming tool by the spacers projecting from said insulating element; h) surrounding the insulating element in the closed foaming tool with a curable plastic mass; i) allowing the plastic mass to cure in the foaming tool; j) opening the foaming tool and removing the now sheathed insulating element, characterized in that the curable plastic mass is an essentially UV stable plastic mass containing at least one dye.