A method for manufacturing composite panels one side of which is intended to be exposed to a climatic environment such as rain, wind, noise, thermal environment such as heat and cold, and the other side facing the inside of a space to be protected, one of these sides at least being covered with paint, and such as: - a metallization is carried out on at least one side of an insulating sandwich panel by the projection of conductive metal in order to obtain a metal film (1, 1') which delimits a conductive area on the at least one side of the insulating panel and which allows the passage of electric current, and the deposition of a polymerizable solid paint powder (3, 3') is carried out on the at least one metallized side (1, 1') on which an electric voltage or a grounding is simultaneously applied, - and by the difference of electric potential between the paint (3, 3') and the totality of the at least one metallized side (1, 1') of the insulating panel, this paint (3, 3') is fixed in a homogeneous manner on the metallized conductive area (1, 1') with different electrical polarity, and this paint (3, 3') fixed by this electrical potential difference is polymerized by placing the panel in an oven characterized in that: - sandwich-type insulating panels comprising at least one insulating core are used - and, to constitute the at least one insulating core, a foam material, having a high melting or degradation point greater than or equal to the polymerization temperature of the paint, is used - alternatively, the metallization by bonding of a metal facing is carried out on at least one side of the insulating sandwich panel, - and the deposition of the paint powder (3, 3') electrically charged at a voltage between 30 and 100 kiloVolts is carried out and, on the at least one metallized side (1, 1'), an electrical voltage or a grounding is simultaneously applied. - a metallization is carried out on at least one side of an insulating sandwich panel by the projection of conductive metal in order to obtain a metal film (1, 1') which delimits a conductive area on the at least one side of the insulating panel and which allows the passage of electric current, and the deposition of a polymerizable solid paint powder (3, 3') is carried out on the at least one metallized side (1, 1') on which an electric voltage or a grounding is simultaneously applied, - and by the difference of electric potential between the paint (3, 3') and the totality of the at least one metallized side (1, 1') of the insulating panel, this paint (3, 3') is fixed in a homogeneous manner on the metallized conductive area (1, 1') with different electrical polarity, and this paint (3, 3') fixed by this electrical potential difference is polymerized by placing the panel in an oven - sandwich-type insulating panels comprising at least one insulating core are used - and, to constitute the at least one insulating core, a foam material, having a high melting or degradation point greater than or equal to the polymerization temperature of the paint, is used - alternatively, the metallization by bonding of a metal facing is carried out on at least one side of the insulating sandwich panel, - and the deposition of the paint powder (3, 3') electrically charged at a voltage between 30 and 100 kiloVolts is carried out and, on the at least one metallized side (1, 1'), an electrical voltage or a grounding is simultaneously applied.