What is the significance of EPS’ low moisture absorptive properties?
Absorption of moisture by insulation materials is partly responsible for some of the variations between published R-values and actual R-values. It is generally recognized that for every 1% of water vapor intrusion into insulation material, thermal effectiveness may be reduced by 7.5%. While fiberglass insulation may have a better initial R-value when lab tested, the comparison changes quickly in field studies. As stated by Oak Ridge National Lab – Dep’t of Energy, “Of all the materials used for insulation, closed cell Expanded Polystyrene is one of the most resistant to the adverse effects of moisture. Unlike other insulation materials, which are easily penetrated by moisture under critical vapor flow conditions, the thermal performance of EPS is only marginally affected by condensation. Even if conden-sation develops through improper use, EPS will retain its dimensional stability and superior insulation values for the life of the structure”. The elimination of water vapor diffusion in
