Why is the very low permeance of closed-cell foam significant?
• It provides protection against moisture transport into the insulation with its related potential for condensation. Vapor on the inside (the warm side) will not come in contact with cold surfaces where the dew point can be reached. • Imperfections in air barriers are less critical with closed-cell foams. • Indoor humidity levels are more easily maintained at healthy levels if vapor cannot escape during dry winter weather.
