Pairs, of course, will be released from expanded polystyrene with the same speed and therefore it is difficult only when condensation in the liquid phase. In fact, such situations are easily prevented by placing the proper specifications and quality control boards, as well as appropriate building design. When designing necessary that the impermeability to water vapor was reduced in the direction of flow required. Consequently, the tightness in the case of exterior walls should be reduced from inside to outside to the inside of the remained dry. Therefore, interference movement of water on the side of the insulating layer, from which steam comes out, is a negative phenomenon. All this is particularly important because the water that enters and remains in Styrofoam insulation layer reduces the efficiency of insulation. This effect is small: for every 1% by volume of water absorbed is lost around 4% of the efficiency of isolation. However, the competent work of the designer and builder, the phenomenon is reversible and allows you to save the thermophysical properties of the material and does not accumulate moisture in the structure.
Water vapor permeability of polystyrene Unlike water steam contained in the air may under certain temperature drops gradually penetrate into the Styrofoam and fall as water cooling. Diffusion resistance (m S) by the product of the drag coefficient of diffusion of water vapor (M) in thickness (S). The coefficient of water vapor diffusion resistance (m) is a dimensionless quantity that indicates how many times the resistance of the material exceeds the resistance of the air layer of the same thickness (for Air m = 1).