Quick answer: XPS (extruded polystyrene) is a rigid, closed-cell foam board made by extrusion. It has a smooth skin, high compressive strength and an R-value of about 4.5–5.0 per inch, making it popular for insulation boards. It uses more material and costs more than EPS, which is why EPS dominates packaging.

What is XPS foam?

XPS stands for extruded polystyrene. Unlike EPS, which is expanded from beads and moulded, XPS is produced by melting polystyrene and extruding it through a die with a blowing agent. The result is a continuous, closed-cell board with a smooth, dense skin on both faces.

Key properties of XPS

What XPS is used for

Insulation boards

Walls, roofs, floors and foundations. XPS's high R-value per inch suits thin-wall situations where space is limited.

Below-grade and wet areas

XPS resists moisture well, so it is often used in basements, under slabs and in other damp conditions.

Flotation and specialist uses

Docks, floats and some craft applications use XPS for its rigidity and low water absorption.

XPS vs EPS

XPS insulates slightly better per inch, but EPS usually costs less per unit of R-value and can be moulded into far more complex shapes. For a detailed insulation comparison, see EPS vs XPS for exterior wall insulation.

Which should you choose?

If you need a thin, high-R-value rigid board for walls or wet areas, XPS is a strong choice. If you need a moulded part, packaging, or the lowest cost per unit of insulation, EPS is usually better — see EPS molds and EPS construction molds. And if repeated impact resistance matters more than insulation, neither XPS nor EPS is ideal: EPP is the better material.

Frequently asked questions

Is XPS better than EPS for insulation?

Per inch, yes — XPS has a higher R-value. But EPS typically costs less per unit of R-value and can be moulded into complex shapes, so the better choice depends on thickness limits and budget.

Is XPS foam waterproof?

XPS is highly water resistant thanks to its closed-cell structure and smooth skin. It is often used in damp, below-grade applications for this reason.

Is XPS the same as Styrofoam?

Styrofoam is a brand name for a type of extruded polystyrene, so it is closely related to XPS. EPS is a different material, made by expanding beads.

Can XPS be recycled?

XPS carries resin code 6 and is technically recyclable, though collection infrastructure for rigid foam is limited in many regions.

Related products and guides

• EPS vs XPS Insulation Analysis
• EPS Mold Manufacturer
• EPS Construction Molds
• EPP Mold Manufacturer