Expanded polystyrene (EPS) and extruded polystyrene (XPS) are both made from the same raw material, but where they differ is the manufacturing process, which gives them different densities.

As XPS has a higher cell density, it has a higher compressive strength and is more moisture resistant. However, there are many situations where EPS is a better option and others where XPS should be considered. Expanded polystyrene EPS is manufactured using foam beads that expand and fuse within a mould using heat or steam. Extruded polystyrene XPS is manufactured using an extrusion process. EPS and XPS provide efficient and effective insulation and guarantee excellent thermal conductivity. Choosing between the two will depend on the particular use. Foamex manufactures both EPS and XPS products in Australia.

Advantages of expanded polystyrene

Expanded polystyrene foam has many benefits. It is lightweight, cost-effective, has excellent thermal insulation, and is strong and durable, moisture resistant, environmentally safe, and recyclable.

Lightweight: EPS is 98% air, so it is light and easy to handle and transport.

Cost-effective: EPS is relatively inexpensive compared to other insulating, void filling, packaging and construction materials.

Thermal insulation: Due to its closed cell structure, EPS has exceptionally low thermal conductivity.

Strong and durable: Numerous studies and reports confirm that expanded polystyrene has high compressive strength.

Moisture resistance: EPS is a closed-cell material that does not readily absorb water. It will maintain its shape, size, and structure even after prolonged water saturation.

Environmentally safe and recyclable: EPS is non-toxic and inert, contains no CFCs or HCFCs, and does not attract vermin. Polystyrene recycling is undertaken by Foamex and other organisations where facilities exist.

Benefits of extruded polystyrene foam

Extruded polystyrene is a versatile and high-performance material. It shares many characteristics with EPS, but as it has a greater cell density, it has a higher compressive strength and is more resistant to moisture.

Like EPS, it is lightweight, an excellent thermal insulator, recyclable and environmentally safe. Its added benefits include:

Higher compressive strength: XPS' closed-cell structure and robust composition make it strong and resilient, able to withstand heavy loads without compromising its insulation capabilities.

Superior moisture resistance: XPS remains dimensionally stable and effective when exposed to water.

Manufactured from recycled EPS: Foamex manufactures XPS using 100% recycled EPS collected from building sites and StyroCycle bins where consumer packaging is deposited.

How is EPS made?

Expanded polystyrene is a rigid cellular plastic foam material derived from petroleum and natural gas by-products.

The raw material, styrene, is produced from benzene and ethylene and is polymerised in the presence of catalysts, usually organic peroxides. To create the expanded polystyrene blocks and sheets, steam is applied to tiny grains or styrene beads containing a minute amount of pentane. This steam process causes the thermoplastic polystyrene to soften and expand up to 40 times its original volume. Again, using steam in the process, the expanded beads are moulded into a shape or large blocks and then sliced into boards. The EPS expanded polystyrene product is dried and finished using several methods, such as hot wire cutting or lamination.

How is XPS made?

Extruded polystyrene is manufactured using an extrusion process. It begins as polystyrene crystals combined with additives and a gas-blowing agent. The materials are fed into an extruding machine, where they are blended and melted into a thick liquid processed through a die. The liquid is expanded into foam, shaped, cooled, and trimmed.

How to choose between EPS and XPS

When selecting the right polystyrene for your needs, evaluate the importance of key factors such as compressive strength, moisture retention, and insulating capability to ensure that you’re making the most cost-effective decision and material choice.

One key difference is the compressive strength. Confirming with your engineers and project managers the required compressive strength for the job will enable you to make an informed decision regarding which polystyrene to use. It’s essential to ensure that your material has adequate compressive strength to withstand day-to-day loads, but going too high can mean a dramatic cost increase for very little, if any, gain.

Foamex’s Australian-made EPS is a well-proven insulation material for commercial and residential construction applications, from floors to internal walls, cold room insulation, and even landscaping. It is sold as expanded polystyrene sheets for insulation, retail signage and event props, foam blocks for void filler and cold room storage, waffle pods for under-slab insulation, and EPS packaging.

XPS foam has superior compressive strength and higher long-term R-values. It is suitable for use on floors subjected to engineered loads and constant traffic and as insulation for inverted roofs, green roof preparation, parking decks, and commercial purlin insulation roof spacers. Extruded polystyrene sheets are commonly used for slab edge insulation to prevent thermal bridging around the perimeter of a home and under residential or commercial concrete slabs to provide additional insulation benefits.

EPS or XPS from Foamex

The use of EPS and XPS insulation in commercial and residential buildings offers great flexibility, compatibility, and thermal efficiency for all areas of a building envelope. Choosing between the two will depend on the particular use, but selecting the appropriate type is critical for proper insulation performance. Cost, availability, and specific performance features can all impact your decision.

At Foamex, we’ve supplied builders, architects, designers, civil engineers, civil contractors, landscape contractors, and landscape designers for many years. Contact our experienced sales team today for a quote or more advice on your next project.

Architecture & Design Team

The Foamex Group

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