Insulation: Good, Better, & Best

By: Terry Meier, Sales Representative, Architectural Products

Some choices are good but others are better. Just because something is good is not necessarily reason for selecting it.

Many years ago the Sears Roebuck catalog would display some of its merchandise in 3 degrees of quality: good, better, and best.

As we consider various choices, we should remember that it is not enough that something is good. Other choices are better, and still others are best.

For over 30 years I have sold XPS foam products. I am very familiar with that product. I believe that XPS is a good product and better than many other insulation products, but is it the best choice? I don’t believe so. Even though I believe that XPS is a good product I would never have it as my first choice. Why? Because I believe that Foam-Control PLUS+® architectural EPS insulation is not only better but it is the best choice. Listed below are 6 reasons why I believe EPS is the best choice:

1. Insulation Value

  • Excavated after 15 years as side-by-side below-grade foundation insulation, the EPS had maintained 94% of its published R-value whereas XPS only retained 52% of its published R-value.
  • The R-value warranty for Foam-Control PLUS+® 250 is R-4.35 and will remain the same through its lifetime. The R-value warranty for XPS is R-value 4.35, the same as Foam-Control PLUS+® 250.

 2. Strength Characteristics

  • EPS is made in 10, 12, 15, 20, 25, 40, and 60 psi strengths.
  • XPS is made in 15, 25, 40, 60, and 100 psi strengths.
  • A wider variety of densities and strengths are available with EPS.

3. Size Availability


  • Widths 8”, 12”, 16”, 24”, 36”, 48”
  •  Lengths 2’, 4’, 6’, 8’, 9’, 10’, 12’, 16’

Thicknesses ½” up to 36” in any variation.


  • Widths 16”, 24”, 48”
  • Lengths 8’
  • Thicknesses ¾”, 1”, 1 ½”, 2”, 2 ½”, 3”

XPS is very limited in sizes and availability.

EPS is manufactured in large blocks and using hot wires are cut into desired size and shape.

4. Product Availability

  • EPS is manufactured locally with very short lead times.
  • XPS is manufactured in very few locations and has long lead times, up to 3 weeks from the time of order.

5. Water Absorption

Foam-Control PLUS+® architectural EPS insulation will absorb a maximum of 2-4% by volume when exposed to the testing specified by ASTM C578.

Recent independent testing of below-grade insulation was conducted on water absorption of expanded polystyrene (EPS) and an extruded polystyrene (XPS). Samples of EPS and XPS were excavated from the exterior foundation of a building in St. Paul, MN. The insulation was placed into service in 1993 and had 15 years of use as a vertical insulation.

Samples were tested immediately upon excavation for R-value and moisture content.

The results of the independent testing are dramatic. The EPS insulation maintained 94% of its stated R-value and had a moisture content of 4.8%. However, the XPS retained only 52% of its stated R-value and had 18.9% moisture absorption.

Short term laboratory tests of water absorption for XPS do not necessarily reflect the long term below grade performance of these materials.

6. Insect Resistant

Termites and other tunneling insects love to live, work, and eat in comfortable and protected surroundings. All untreated foam insulation products can provide this environment. Foam-Control PLUS+® can be made using a patented process using a borate mineral that is a deterrent to tunneling insects such as termites. This additive is incorporated into the foam insulation during the manufacturing process. It is safe for handling and is noncorrosive.

XPS foam is not available with this additive and is susceptible to insect intrusion.

7. Cost Per R-Value

  • At equal R-value EPS costs about 30 – 50% less than XPS.
  • When EPS is that much less expensive than XPS the choice is easy.  This choice is especially easy when there are no advantages in choosing XPS.
  •  Foam-Control PLUS+® architectural EPS is by far the best choice.

But don’t just take our word for it…

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