The method includes applying a heat reflective coating to a substrate sheet of construction material and air drying the heat reflective coating on the construction material. The method is directed particularly to the coating of insulation material, such as fiberglass batts, at the time of manufacture, but may be applied to virtually any sheet of material in order to improve the insulation properties and structural value of the material. By completely encapsulating fibrous insulation material with the impervious heat reflective coating, the emission of irritant fiber particles and corresponding health hazards are eliminated. Also, the efficiency of the insulation material is improved by sealing out moisture when completely encapsulated by the coating.