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Which Insulation is better XPS or EPS
Which Insulation is better

For years people have thought XPS is superior to EPS - is it really?

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Reasons Why EPS Insulation is Superior
The Facts
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Higher R-Value Rentention

EPS does not suffer from the same plight as XPS in regards to “Off Gassing.” XPS has blowing agents that initial give it a higher R-value, but these gasses escape over time lowering the R-value. The off gassing of XPS is not just a one time event. This loss is a gradual escape of gasses into the surrounding environment. With the gasses goes the R-value loss of the insulation as well. The real question is how much does it go down, how fast and over what period. Long Term Thermal Performance (LTTR), is a measurement to try and quantify these losses but it does not take into account the shrinking R-value after the first 5 years. (Learn More About LTTR)

Buildings are designed and built to last 50-100 years in most cases. If LTTR only gives use a clear picture of the first 5 years of insulation performance, how does that information effect the economies of the building? Does it cost more to operate than expected? Did we over pay for a insulation that has a shrinking R-value? Are their long-term health impacts from the off gassing? (News About LTTR)
What is the real R-value of XPS Insulation
Off Gassing
Off Gasing in Insulation
Lowers R-Value in Insulation
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Plymouth Foam's Engineered EPS can be made in various densities and can achieve compressive strength up to 8,640 lbs/ft and flexural strength up to 10,800 lbs/ft. It is amazing that such a light product, that is 98% air, is so strong.

Exposure of EPS to moisture resulting from such factors as periodic, internal condensation or moist soil conditions in foundation applications do not affect the mechanical strength characteristics of EPS thermal insulation board. Even the freeze/thaw cycle doesn't seem to effect EPS. View study

EPS has another advantage over XPS insulation in that a laminated poly facer can be applied to the board. This high performance poly facer increases durability, fastener holding and impact resistance. Our Poly facers come on both sides of the insulation and can be manufactured using clear or reflective facers. Facers can be all clear, all reflective or clear on one side, reflective on the other.
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EPS and XPS at same densities are similar in durability but add a facer and EPS is superior.
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Moisture Management

EPS rigid insulation is closed cell and has a high tolerance to resist moisture. In fact, in field studies, EPS has been shown to absorb less moisture than previous considered. The study proved that EPS absorbed only 1/2 of a percent (.005) over 15 years in a below grade field study. When water does enter the microscopic cavities, Expanded Polystyrene has the great property of allowing moisture to expel out. EPS insulation exhibited drying potential under severe exposure conditions while other insulations like XPS, when exposed to the same conditions, did not. Read More

Due to all the properties of EPS, this rigid insulation makes the perfect moisture management product for various application, racially below grade. Both EPS and XPS products resist moisture but only EPS has the great ability to expel it.
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Both XPS and EPS resist moisture but only EPS expels it easily
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100% R-Value Warranty

XPS warranties 90% of its R-value. EPS warranties 100% of its R-value. These of course are under the conditions of the warranties. (see XPS Warranties) The reason for the differences is really the Off gassing and the dropping of the R-value in XPS insulation. EPS does not suffer from dropping R-value, therefore it can give the full 100%.

* Published R-Values come directly from the manufacturer’s publications. XPS R-values were used from Owens Corning and Dow. Guaranteed R-value was from XPS Manufactures publication - See Warranties.
Why get 90% when you can get 100% Warranty
Are you getting what you paid for?

XPS 90%
EPS 100%
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Harmful Chemical HFCs

Hydrofluorocarbons (HFCs) are listed as a Volatile Organic Compound (VOC). XPS contains HFCs, EPS does not. As a VOC, HFCs has a high GWP (global Warming Potential) as high as 3000 times more than that of carbon dioxide. At a global level, releases of HFCs have serious environmental consequences as it can stay in the atmosphere for hundreds of years.

Imported XPS may contain HCFCs as many developing countries are not under the same manufacturing restrictions as the United States. HCFCs, although not as stable and therefore not so persistent in the atmosphere as CFCs, HBFCs or Halons, they can still end up in the higher atmosphere (stratosphere) where they can destroy the ozone layer, thus reducing the protection it offers the earth from the sun's harmful UV rays. HCFCs also contribute to Global Warming (through "the Greenhouse Effect"). Although the amounts emitted are relatively small, they have a powerful warming effect (a very high "Global Warming Potential").

Some VOCs are dangerous to human health and breathing in these compounds have not been fully studied or understood as to the effects on human health. (More About VOCs)

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EPS does not
contain HFCs, HCFCs, or CFCs
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The difference in cost between XPS and EPS can range from 20% - 40%. EPS is always less, but more importantly it less per R-value inch as well. (by the numbers) In fact, EPS is the best value in rigid insulation.

Many building profession are learning the facts and costs of EPS and are starting to Value engineer projects (Value Engineering EPS) Recently a contractor saved $1000 on a project by just switching from XPS to EPS. (See how he did it) With all these advantages, what is keeping you from using more EPS?
EPS insulation best price

Learn to Save with EPS
20% - 40%

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Superior Bonding Capability

During the manufacturing process, XPS and EPS provide a far different exterior surface. XPS almost has a skin, which makes bonding to that skin less desirable. EPS on the other hand has a surface that excepts bonding very well. In fact, the Insulated Concrete Forms (ICFs), Exterior Insulated Finish System (EIFS) and the Structural Insulated Panels (SIPs) industries have found EPS to have exceptional bonding capability. These building components industries prefer EPS and believe the product is far superior to XPS. The packaging industry has also found EPS exceptional for component bonding. High end packaging prefers EPS because of its physical bonding capability.
EPS has better bonding capabilities

EPS is far superior in bonding capability to XPS

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Made in Wisconsin

Plymouth Foam’s EPS is proud to made in Wisconsin. Our state has one of the best educational system in the country and it shows in our workforce. We provide many local jobs and help boost our economy. (Made in Wisconsin)

Some of the XPS is made in China or other parts of the County. But Plymouth Foam is proud to say, our EPS insulation is Made in the USA.
Buy local  Made in Wisconsin and Made in the USA


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More Customizable

The building industry is requiring more customization of products. The 4’ x 8’ sheets are ok, but more and more building professional are looking for more. Basement wall heights of 9’4” as an example, wouldn’t one piece covering the 9’4” height be better. EPS is far superior in its ability to make custom sizes, shapes and thicknesses. XPS is limited to 3” - 4” thick, where EPS can be made up to 48” thick. XPS is limited to R-15, where EPS can go up to R-209.

EPS can add lamination to its products, such as reflective facer in fan-fold. Tongue and grove, ship lap, groves, channels, wire case are just a few items that be added to EPS. The possibilities are almost endless with EPS. (See More Customization of EPS)
EPS insulation can be custom made

The possibilities with EPS are almost Endless

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Lower Smoke Development

ASTM E84 is the test method for surface burning characteristics of building materials. This test covers flame spread and smoke development. Polystyrenes (XPS & EPS) have very similar characteristic when it comes to the introduction of fire. Flame spread is identical but EPS has a lower flame spread. Some would believe in simple terms that EPS is 98% air with no blowing agent. Both products do meet the IBC requirement for building products.
EPS insulation smoke development

Smoke development is slightly lower in EPS

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Lower Global Warming Potential

The Global Warming Potential (GWP) was developed to allow comparisons of the global warming impacts of different gases. According to the US Environmental Protection Agency,” the larger the GWP, the more that a given gas warms the Earth compared to CO2. GWPs provide a common unit of measure, which allows analysts to add up emissions estimates of different gases.” (EPA - Green House Gas Emissions) The chemical compound HFCs contribute XPS having a higher GWP than EPS.

Transportation accounts for 26% of gas emissions, so buying EPS locally can help reduce gasses even more. (EPS Reduces Global Warming)
EPS Insulation can reduce harmful gas emissions

EPS helps reduced utility usage lower harmful gas emissions

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Recycle Accessibility

EPS has the advantage of being 100% recyclable and having an infrastruction in place to accomplish it. There are recycling centers all over the US just for EPS. In fact, there are over 200 EPS collection centers and growing. Last year in 2016, over 118 million pound of EPS was recycled. That is a ton considering EPS doesn’t weigh that much as 98% of the product is air. Learn More

Fact: in 2013, over 34% of post consumer EPS was recycled

Learn More Plymouth Foam Recycle Center
Nation Wide Drop Off Centers
Video Recycling EPS

Post Consumer EPS Recycling Rates

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Note: EPS Type IX and XPS Type IV, both 25 psi material were compared

Disclaimer of Liability
Technical information contained herein is furnished without charge or obligation and is given and accepted at recipient’s sole risk. Because conditions of use may vary and are beyond our control, Go Plymouth makes no representation about, and is not responsible or liable for the accuracy or reliability of data associated with particular uses of any product described herein.

Go Plymouth believes the information and recommendations herein to be accurate and reliable. However, since use conditions are not within its control, Go Plymouth does not guarantee results from use of such products or other information herein and disclaims all liability from any resulting damage or loss. No warranty, express or implied, is given as to the merchantability, fitness for particular purpose, or otherwise with respect to the products referred to.
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Compressive Resistance at 10%
Higher R-Value Retention 1
Harmful Chemical HFC
Greater R-Value Actuality 2
100% R-Value Warranty
Made in Wisconsin
Lower Global Warming Potential
Superior Bonding Capability
Better Moisture Expelling
Lower Smoke Development
More Customizable
The Winner Is
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25 PSI

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25 PSI