EPS Insulation vs XPS Insulation

Insulation materials are available in several forms. They’re ideal for application as insulating concrete foam (ICF). Rigid foam is among the most commonly used insulation.

There’re several types of rigid foam, with the most preferred types being extruded polystyrene (XPS) and expanded polystyrene (EPS).


EPS Insulation vs XPS Insulation

EPS and XPS have some similar properties. For instance, both are made from a material known as polystyrene resin. Also, both utilize trapped air within the foam as the insulating medium.

Besides, both feature a closed-cell kind of structure. Besides, they’re manufactured using the same standard.

Although they have certain similarities, they also have some differences. They’re both made using the same kind of polystyrene material, but their manufacturing process differs in various ways.

The manufacturing process of EPS uses a special blowing agent known as Pentane and steam to form cellular structures. The cellular structures are formed through a foaming process, whereby Pentane expands resin beads, remolds them into several blocks, and cuts them into the required sizes.

On the other hand, the manu     facturing process of XPS involves melting polystyrene resin with the help of an extruder. Next, the melted resin is expanded with the help of blowing agents known as hydrochlorofluorocarbons (HCFCs).

The different processes of making XPS and EPS insulation lead to their key differences including the cost in terms of R-value, moisture resistance, compatibility, eco-friendliness, and compressive strength.


Cost in R-Value

R-value is a measure of the insulation ability of a material. A higher R-value indicates the material has better insulation properties. There’s a standard method used by manufacturers to test an insulator’s R-value.

The testing method requires the technician to take the value of the thermal resistance of an insulation foam by placing it between a hot and cold plate.

Although rigid foam offers great R-values, some options offer better thermal performance than others. For instance, EPS insulation offers better insulation for finishing systems, exterior insulation, structural insulated boards, and ICFs.

Although it has a lower R-value per inch (R-4), its R-value varies with varying densities. If an insulation product has a higher density, it’ll have a higher R-value.

When comparing XPS and EPS insulation, EPS is about 10% to 30% less expensive than XPS. EPS costs approximately 19 cents for every square foot.


Moisture Resistance

The extent to which an insulation material resists moisture is extremely important, especially when looking for a material that can enhance the insulation of a property.

If an insulation product has a low moisture insulation level, it may retain a lot of moisture. As a result, it may get damaged and lead to the formation of bacteria and mold. If bacteria forms on the insulation, it may cause various health issues.

When comparing XPS and EPS in terms of moisture resistance, EPS proves to be better at resisting moisture.

However, the methods used by various manufacturers to test an insulator’s moisture resistance vary considerably. Thus, it’s quite challenging to have an accurate comparison between them.

XPS manufacturers typically test their insulation using a controlled underwater test. The test involves submerging the material in water for a few hours, usually between 2 to 24 hours per test. The exact testing time depends on the kind of XPS product being tested.

Testing water resistance with this method shows that XPS has a better water resistance than EPS. Although XPS absorbs moisture more slowly, it releases the absorbed moisture more slowly than EPS. Thus, XPS retains any absorbed moisture for a longer period than EPS.

In real-life testing, the two insulation products were installed in a commercial property and extracted after 15 years. Upon extraction, the two products were tested for the amount of moisture within them.

Test results showed that EPS had a moisture content of 4.8% whereas XPS had a moisture content of 18.9%. These test results prove that XPS retains more moisture than EPS.

Additionally, the researchers left the two insulation products for 30 to dry and tested their moisture content. Test results showed that XPS had a moisture content of 15.7% while EPS had a moisture content of 0.7%.

For applications where the product is exposed to a lot of water, choose special insulations that have precut drainage grooves that prevent moisture penetration or those with facers that enhance water resistance.

These features are also useful in minimizing the pressure of the backfill. They also assist in keeping water out of the foundation.



XPS is preferred for insulating concrete buildings. Regardless, EPS also offers reliable insulation in concrete buildings. EPS is also found in structural insulated panels.

Generally, both XPS and EPS are great options for insulating exterior walls. Also, they work with numerous building materials as long as they’re installed correctly.



Today, there’s an increasing focus on building green homes. Thus, it’s important to consider green construction materials when building a home or commercial property.

Generally, both XPS and EPS are eco-friendly. However, they contain a blowing agent that’s used during the manufacturing process. For instance, EPS uses Pentane as the blowing agent.

Pentane’s global warming effect is extremely low. Besides, EPS doesn’t contain dyes. Also, it contains some recycled ingredients (about 15%).

The process of making XPS uses blowing agents referred to as HCFCs. HCFCs have a significant global warming effect. Also, HCFCs release toxic gases like carbon dioxide when burnt.

XPS loses its insulation properties over time since the gas that’s trapped inside escapes slowly in a process referred to as off-gassing. Consequently, several XPS manufacturers are shifting from using HCFCs as the blowing agent and opting for safer blowing agents.

Also, XPS insulation contains dyes that assist in distinguishing it from other products. However, the dyes aren’t environment-friendly.


Compressive Strength

Compressive strength indicates how well an insulation product can withstand pressure before it starts breaking. XPS and EPS have compressive strength ranging from 10 to 60 psi. However, XPS is also available in a 100 psi option.

Since insulation with a higher psi costs more, it’s important to know the best option for your budget and needs. In several instances, insulations with a lower compressive strength offer sufficient insulation and will save you some money.

Since EPS is proved to have a lower level of compressive strength, it’s more affordable than XPS. However, if the application requires insulation with a compressive strength of 100 psi, then you can only use XPS.


Final Words

Both EPS and XPS offer contractors and builders dependable insulation. However, the best insulation between the two depends on the specifications of a project such as compatibility, eco-friendliness, compression strength, R-value, and moisture resistance.

Regardless of the option a builder chooses to work with, it’s important to ensure the insulation product meets the required standards.



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