Thermal Insulation

Manufacturer:  Dow Chemical
Address:  2030 Dow Center, Midland, MI 48674
Phone:  (800) 447-4369
Web Site: www.dow.com

Product Name:  Styrofoam (expanded), Styrofoam Square Edge (extruded)
Insulation Classification: Foam Insulation
Thickness As Tested: 1.00"
Claimed "R" Value: N/A (expanded), 5.0 (extruded)
Actual "R" Value (at product thickness): 3.84 (expanded), 4.92 (extruded)
Equivalent "R" Value (per inch): 3.84 (expanded), 4.92 (extruded)

Product Overview
Dow Chemical's "Styrofoam" brand name encompasses a wide range of polystyrene-based insulation products.  Included in our testing were two versions, the common white "expanded" product and the "extruded" Styrofoam Square Edge (see photo).

Styrofoam (expanded)- This is the product most people think of when they hear "Styrofoam".  It is white in color and comprised of thousands of individual "beads" which are pressed together.  The most common use is as a cushioning material in shipping and packaging.  Although it is not intended for use as an insulation, it frequently is.  Most people have seen cheap coolers and ice chests made from it.  As an insulation, expanded Styrofoam has many qualities which count against it.  At R 3.84 per inch, the product is simply not a very good insulator.  Secondly, it is very hygroscopicity (absorbs and holds moisture).   This tendency to get, and stay wet,  makes it something to definitely avoid when looking at ice box insulation.

Styrofoam Square Edge (extruded) - This product is often called "blueboard" due to its light blue color.  In spite of its relatively modest "R" value (4.92 per inch), Styrofoam SM is our overwhelming recommendation for foam ice box insulation in marine applications.  Unlike its expanded cousin (above)and virtually all other foam insulation, Styrofoam "Square Edge" is completely impervious to moisture.  This is a huge plus.  While many other foams start out as better insulators, they inevitably suffer significant decline as they absorb moisture from the surrounding air.  This is not the case with Styrofoam SP.  Another benefit of its hydrophobic nature is that no "air gap" is required when installing it.   This means that more insulation can be packed into a smaller space. If is available in many thicknesses and two sheet sizes.

Test Conclusion
As the fifth largest chemical company in the world, Dow does not need to oversell their products or exaggerate their qualities.  Unfortunately, misapplication of expanded Styrofoam has led many people to think of the brand as offering poor insulation value and high moisture absorption.  As previously stated, expanded polystyrene is not a suitable insulation for moist environment.  However, the extruded version, Styrofoam Square Edge, is another story entirely and we recommend it highly whenever a standard insulation foam is required.

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