All that Glitters is Not Gold: How Stable is your R-Value?

By: Doug Wehrwein, Sales Representative

It’s generally understood that extruded polystyrene (XPS) offers more initial R-value per inch than expanded polystyrene (EPS) yet because of its lower cost, EPS offers a better value.

Are you aware that XPS manufacturers use blowing agents made with CFCs and HCFCs which have a negative effect on our environment because they are contributing to the depletion of the earth’s protective ozone layer? Besides this negative effect on our environment these blowing agents linger in XPS rigid insulation and temporarily boost its R-value. But it won’t last… the XPS manufacturers guaranty it won’t last!

XPS manufacturers’ warranties state that the R-value, they so proudly promote as R-5 per inch, will only be retained at 90%. 90% of that R-5 is 4.5. In other words, XPS is guaranteed to lose R-value. Is less than a .023 percent increase in R-value worth a 10 to 20 percent increase in cost?


All that glitters is not gold is a well-known saying, meaning that not everything that looks precious or true turns out to be so. I encourage you to check into the R-value warranties of the 4 pretty pastels, the green, yellow, pink and blue colored XPS rigid insulation products. They all guaranty that their rigid insulation boards will lose R-value.

On the other hand Foam-Control PLUS+ rigid EPS insulation maintains a consistent R-value over its life because the manufacturing process used to manufacture EPS contains no ozone depleting blowing agents and results in just normal air, rather than gas, being encapsulated within the closed cell rigid insulation. Foam-Control PLUS+ architectural insulation is stable and the R-value will not change over time.

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