Insights on Insulation: Expanded (EPS) vs. Extruded (XPS) Polystyrene


Choosing between expanded polystyrene (EPS) and extruded (XPS) polystyrene insulation comes down to different factors for construction professionals. For many designers and builders, they’re looking for a product that hits the sweet spot: where high-performance building protection and value meet.

Deciding to go with either EPS vs. XPS insulation can be made easier when you understand how each material performs.

The building industry is slow to change, so pros often rely on what they’ve always used. However, you might be overspending on materials: While XPS appears to offer a high initial R-value per inch and high strength, it comes at the expense of a higher cost. Let’s take a look at both products in more detail.

EPS vs. XPS Insulation Manufacture and Blowing Agents

To understand how these insulation materials perform, it helps to know how they’re manufactured.

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Extruded polystyrene (XPS) insulation is created through an extrusion process, where HFC blowing agents, colorants and other additives are melted together to form a liquid. That liquid is extruded through a die, and when cooled, it forms a rigid insulation panel.

A solid polystyrene is also used to manufacture expanded polystyrene (EPS). The polystyrene, which contains a hydrocarbon blowing agent, is expanded and molded with steam into molded polystyrene boards or insulation panels.

The result of either the extrusion or expanded process is closed cell polystyrene foam. However, the use of a hydrocarbon compared to an HFC blowing agent provides a clear environmental advantage to EPS.

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Breaking Down Your Insulation’s Performance

Both types of insulation can provide you with a highly insulated building envelope for a more energy-efficient space, but there are a few key differences in their performance.

Understanding what’s needed for a high-performing, code-compliant building envelope might help you determine what to invest in your insulation. There are a few key factors when deciding on EPS vs. XPS insulation.

Thermal Resistance Over Time

Extruded polystyrene (XPS) has a higher initial thermal resistance per inch compared to EPS, but this resistance degrades over time as the blowing agents in XPS escape. Recent industry research indicates the R-value of XPS is near 4.3 per inch after 50 years.

EPS has a stable, long-term R-value that does not degrade over time and provides enduring thermal protection for the lifetime of your structure. ThermalStar® insulation is available with R-values as high as 4.5 per inch and these R-values are stable from the day of purchase through 50 years. This means some ThermalStar® products have a higher long term R-value than XPS.

Cost-Effective Conservation

EPS is a popular choice with designers and builders because it allows for a cost-effective solution to insulation as it is available at a lower cost than XPS. However, like XPS, expanded polystyrene insulation is readily available in multiple grades from 10-60 psi to meet all your application needs, from below-grade to walls and roofs.

Win Over Clients With Better Insulation

There are a few ways that expanded polystyrene insulation provides more solutions for your building envelope than an XPS product you might have been using before. Here’s a recap:

  • EPS provides a more sustainable solution for insulation.
  • ThermalStar® Rigid Insulation from Atlas Molded Products is available from 10-60 psi to meet all your application needs.
  • ThermalStar® Rigid Insulation products provide a stable R-value for 50 years.
  • ThermalStar® Rigid Insulation products provide a solution where high-performance and value meet.

Expanded polystyrene gives designers and builders an easy, energy-efficient, cost-effective answer to their insulation needs. EPS products from Atlas come in a variety of applications, combining block and shape molding for whatever your building requires to stay protected (all while saving you money).

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Whether you’re designing an interior or exterior application, you can work directly with Atlas Molded Products to find a workable, affordable solution for your building. Our team will help you ensure you get the best possible product for your budget. Connect with your regional team member here.