XPS vs EPS Rigid Foam Insulation What's the Difference?

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There are two types of rigid polystyrene foam plastic insulation, extruded (XPS foam), and expanded (EPS foam). Although both types of insulation are comprised of polystyrene, the two types of manufacturing processes produce finished products with very different performance properties.

The most important characteristic of insulation is its ability to retain R-value and continue to insulate even when exposed to water for long periods of time. Over the lifetime of a building or paved surface, water gets into, and lingers in, the soil around the construction. Water is an excellent conductor of heat, so if insulation is water soaked, R-value is lost. Also, if absorbed water freezes and thaws, the insulation structure will break down over time and structural integrity can be compromised.

There is extensive messaging from the EPS industry claiming that EPS performs the same, if not better, than XPS when it comes to R-value and moisture. But you only have to look at the science to see the real truth – science doesn’t lie.