What is the Difference Between Expanded and Extruded Polystyrene?

The main difference between Expanded Polystyrene (EPS) and Extruded Polystyrene (XPS) lies in their density, production process, and insulating properties. Here are the key differences between the two:

1. Density: Extruded polystyrene is denser than expanded polystyrene, with an average density of 2.18 lbs for XPS and 0.93 lbs for EPS.
2. Production Process: EPS is manufactured by expanding spherical beads in a mold and then using heat and pressure to fuse the beads together. In contrast, XPS is produced via an extrusion process, where plastic resin and other additives are combined and extruded into its final shape.
3. Insulating Properties: EPS has a more irregular cell structure, allowing air and moisture to permeate the foam, making it less suitable for moist environments. XPS, on the other hand, has a closed-cell structure with tightly packed cells, which helps prevent air and water ingress, making it more ideal for moisture management.
4. Strength and Rigidity: EPS foam is less dense and rigid than XPS due to the voids or spacing between its cellular structures. XPS foam is extremely rigid and strong, making it ideal for structural panels.
5. Thermal Performance: XPS has a slightly better thermal performance than EPS, with an R-value of about R-5 per 25 mm for XPS and roughly similar performance for EPS. However, EPS with the same level of density is less expensive.
6. Cost: EPS is generally less expensive than XPS.
7. Environmental Impact: EPS is considered to be superior in terms of environmental impact, as it can be constructed with recycled content and does not use any type of dye. In contrast, XPS typically contains dyes and branding elements.

In summary, EPS is a more affordable, lightweight, and less dense insulation material, while XPS is denser, stronger, and more rigid, with slightly better thermal performance and moisture resistance. The choice between the two materials depends on the specific requirements of the project, considering factors such as insulation performance, moisture management, cost, and environmental impact.

Comparative Table: Expanded vs Extruded Polystyrene

Expanded Polystyrene (EPS) and Extruded Polystyrene (XPS) are both types of foam insulation made from polystyrene, but they have different properties and applications. Here is a table comparing the key differences between EPS and XPS:

EPS is a lightweight, versatile insulation material with high mechanical resistance, making it suitable for various applications, including decorative elements. XPS, on the other hand, is denser and more rigid, making it ideal for structural applications like SIPs and ICFs. EPS has a lower R-value and thermal conductivity compared to XPS, but it absorbs more moisture and has a lower environmental impact during production.