Wind Penetration Through Fabric Systems—Part II

Abstract

The earlier study of spaced double windbreak layers was extended to determine the decrease in effectiveness of such systems when porous materials are used in the inter vening space to insure positive separation of layers. It was shown that mesh spacers caused little decrease in the efficiency of the system. Lower values of heat transfer coefficients were obtained by keeping the air penetration through the outer windbreak within the air handling capacity of the space than by letting large quantities of air into the space and blocking further penetration with an inner windbreak of low permeability. Where there was little penetration of the outer windbreak layer, the still air in the air space increased the insulation over that where the layers were unspaced. Results with loose-fitting systems were found to be similar to those for tight-fitting systems, provided that penetration of the inner windbreak was not excessive. Finally, the laboratory findings were cbrroborated by a field study of clothing incorporating the spaced-windbreak principle.