Several tests and studies has proved that STYRO EPS insulation material installed in well-constructed roofs does not absorb appreciable moisture, even under conditions characteristic of prolonged, cold, damp winters. The small amount of moisture absorbed (an average of 0.2% by weight) has little or no effect on the compressive or flexural strength and the STYRO EPS insulation retains between 95% and 97% of its thermal efficiency.

Though STYRO EPS has low water vapor transmission, STYRO EPS is not a vapor barrier. Rather, it “Breathes” and, therefore needs no costly venting as do some other relatively impermeable insulation materials which could otherwise trap moisture within walls and roof assemblies.