Expanded Poly Styrene

This is published information on the effects of UV exposure to expanded polystyrene (EPS) foam insulation. Prolonged exposure to the sun may cause slight discoloration and surface dusting of EPS foam. This will not significantly affect its insulating properties. It is suggested that EPS, when stored outside, should be protected with a light-colored opaque material.

We recommended EPS be covered within 60 days at which time color fading and/or surface dusting may occur. The rate at which ultra-violet light affects polystyrene affects is consistent with geographical and weather influences.

There are (3) stages of polystyrene reaction to UV exposure:

  1.  Fading and/or discoloration happens within 2-4 weeks and depends on exposure rates. *This does not impact physical performance properties in any way.
  2. Dusting is the result of the thin layering covering the surface which can deteriorate the outermost structure of the polystyrene. *This does not impact the integrity of the overall material.
  3. An extended period of exposure can result in deterioration, the material thickness can erode to a point where r-value loss is possible due to the proportional reduction in insulation thickness.

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