Austech Foamular extruded polystyrene vs. expanded polystyrene

News /
5 March 2010

Austech investigates what sets Foamular extruded polystyrene apart from expanded polystyrene.

There is often a great deal of confusion between expanded (EPS) and extruded polystyrene(XPS), with many people assuming they are essentially the same, but in fact expanded and extruded polystyrene are very different products.

Firstly there is the manufacturing procedure involved in creating the product. Expanded Polystyrene (EPS) is made using small expandable beads that inflate with heat, and then are placed into a mould, where they expand to fit the shape. The expanded beads trap air, which gives expanded polystyrene its insulation properties, but also leaves it venerable to water absorption, reducing the insulations effectiveness over time.

Extruded Polystyrene (XPS) is made by mixing polystyrene pellets with chemicals that liquefy the pellets. A blowing agent is then injected into the mixture, forming billions of miniature air pockets. This frothing mixture is then pushed through a shaping die to give the required size and minimise wastage. Once cooled the boards can be further shaped and wastage returned into the manufacturing process.

Foamular Extruded Polystyrene is manufactured by Owens Corning Asia Pacific. Owens Corning has developed a patented Hydrovac technology that makes the blowing agent more efficient and helps guarantee long term retention of R-values. Owens Corning is a member of EPA Climate Leaders program, and is committed to reducing greenhouse gas emissions in the manufacturing process through product performance.

Extruded Polystyrene’s unique production process gives it superior R-value in comparison to expanded polystyrene and many other building materials. This improved effectiveness helps reduce temperature fluctuations and improve energy efficiency for the entire product lifecycle.

R Values of some common building materials:

Foamular metric XPS 250 /50mm = R1.78
Expanded polystyrene 50mm, m grade = R1.20
Brickwork, 110mm = R0.18
Weather boards, 12 mm avg, pine = R0.08
Fibre cement sheet, 6mm = R0.019
Concrete slab, 2400kg/m3, 100mm = R0.069
Plaster board, 10mm = R0.059

Compressive strength is another key advantage for Foamular extruded polystyrene, since it can be used for high pressure applications, such as under slab insulation and in PRMA roofing applications. This structural rigidity also improves the products lifecycle, for instance when Foamular is used as a render substrate, its improved impact resistance and structural strength helps reduce future damage and cracks to the render.

Foamular extruded polystyrene’s closed cell structure stops water absorption, which is a leading cause of loss in R-value in other forms of insulation. Expanded polystyrene does not have a closed cell structure and easily absorbs water, dramatically reducing its thermal properties and its overall structural integrity.

Overall, Foamular extruded polystyrene from Owens Corning outperforms expanded polystyrene (EPS), in the three key areas of R-value, moisture resistance and compressive strength, making Foamular a more efficient and durable insulation product.

Austech External Building Products

Austech specialises in lightweight, external building products including Foamular Extruded Polystyrene, Duratuff Select Vinyl and CraftStone Claddings.

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