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Here at Castle NZ we often get asked “what insulation should I use under my slab?”, and here at Castle NZ we recommend XPS.  XPS boasts a rigid structure, closed-cell construction, and impressive thermal performance, and XPS insulation stands as a cornerstone in enhancing energy efficiency. Below we unpack exactly why you should consider XPS for your next project, but before we begin it’s important to apply a definition around exactly what EPS and XPS are.

Extruded Polystyrene (XPS):

XPS is a type of rigid foam insulation made from polystyrene polymers. The production process involves extruding melted polystyrene pellets through a die to form a continuous closed-cell structure. This extrusion process results in a rigid and durable insulation material with excellent thermal properties. XPS insulation is commonly used in construction for applications such as insulating foundations, walls, roofs, and floors.

Expanded Polystyrene (EPS):

EPS is another type of foam insulation material made from expanded beads of polystyrene. In the manufacturing process, pre-expanded beads are fused together using steam, creating a lightweight and versatile insulation material. The expanded structure of EPS consists of individual beads containing mostly air, resulting in an open-cell structure. EPS is widely used in construction for insulation, packaging, and various other applications.

Superior Strength and Durability

XPS insulation is renowned for its exceptional strength and durability. Its manufacturing process involves extruding polystyrene through a process that results in a closed-cell structure, creating a rigid and robust material. This structural integrity enables XPS to withstand higher levels of compressive strength compared to EPS, making it the preferred choice for applications that require load-bearing capabilities.

Enhanced Moisture Resistance

One of the distinguishing features of XPS insulation is its superior resistance to moisture penetration. The closed-cell structure of XPS prevents water absorption, ensuring long-term thermal performance even in damp or humid conditions. In contrast, while EPS insulation offers good moisture resistance, it can be susceptible to water absorption over extended periods.

Consistent Thermal Performance

XPS insulation delivers consistent and reliable thermal performance over time. Its closed-cell structure and dense composition contribute to maintaining its insulation properties without significant thermal drift. This stability in performance ensures sustained energy efficiency throughout the lifespan of the building. On the other hand, EPS insulation may experience some thermal variation due to its more open-cell structure.

Excellent Compressive Strength

When it comes to areas that experience heavy loads or require foundation support, XPS shines with its impressive compressive strength. With a higher compressive resistance compared to EPS, XPS is an ideal choice for applications where maintaining structural integrity under pressure is crucial, such as under concrete slabs or floors.

Environmental Considerations

Here at Castle NZ we believe in full disclosure, and it’s safe to say that both XPS and EPS are recyclable materials, but the manufacturing process and properties of XPS do result in a higher embodied energy compared to EPS. However, as described above, XPS is known for its long-term durability, potentially offsetting its higher initial energy footprint by providing extended service life.

 In Summary

In summary, while both XPS and EPS offer commendable insulation capabilities, XPS stands out for its superior strength, moisture resistance, consistent thermal performance, and excellent compressive strength. These factors make XPS the go-to choice for applications demanding durability, load-bearing capacity, and long-term insulation efficiency.

When considering your insulation needs, carefully assess the specific requirements of your project to make an informed decision. XPS, with its exceptional qualities, stands as a reliable solution for those seeking top-tier insulation performance.

Here at Castle NZ, we’re proud to offer an XPS insulation solution designed to meet your needs. Contact us today to explore our offerings and elevate your project with the power of XPS insulation, or learn more about XPS here.