Reconsider Prob. 14–74. In order to reduce the migration of water vapor, the inner surface of the wall is painted with vapor retarder latex paint whose permeance is 26 × 10^-12 kg/s · m² · Pa. Determine the amount of water vapor that will diffuse through the roof in this case during a 24-h period.

Data from problem 74

The roof of a house is 15 m × 8 m and is made of a 20-cm-thick concrete layer. The interior of the house is maintained at 25°C and 50 percent relative humidity and the local atmospheric pressure is 100 kPa. Determine the amount of water vapor that will migrate through the roof in 24 h if the average outside conditions during that period are 3°C and 30 percent relative humidity. The permeability of concrete to water vapor is 24.7 × 10^-12 kg/s · m · Pa.