Insulation degrades (experiences an increase in thermal conductivity) if it is subjected to water vapor condensation. The problem may occur in home insulation during cold periods, when vapor in a humidified room diffuses through the dry wall (plaster board) and condenses in the adjoining insulation. Estimate the mass diffusion rate for a 3 m by 5 m wall, under conditions for which the vapor pressure is 0.03bar in the room air and 0.0bar in the insulation. The dry wall is 10 mm thick, and the solubility of water vapor in the wall material is approximately 5 x 10-3kmol/m3 bar. The binary diffusion coefficient for water vapor in the dry wall is approximately 10-9 m2/s.