Air flow is reduced through a structure insulated with one more layers of fiber wool or particulate insulating material. A layer of a foamed fluid polymeric composition is applied onto the exposed surface of the insulation to cover the edges at which the exposed surface of the insulation meets an enclosing member of the structure. The layer is then cured to form a polymeric coating on the exposed surface of the insulation. The coating seals the edge or edges at which the exposed surface of the insulation meets the enclosing members of the structure.