extruded polystyrene sheet

Here at QPOD, we often get asked about under slab insulation and we recommend XPS. XPS boasts a rigid structure, closed-cell construction, and impressive thermal performance whilst being environmentally sound in contrast to it’s less environmentally desirable alternative, EPS.

Below we unpack exactly why you should consider XPS for your next project, it’s important to apply a definition around exactly what EPS and XPS are.

XPS: Extruded Polystyrene Sheet


XPS, or extruded polystyrene yields a continuous closed-cell structure. The meticulous extrusion method used in it’s construction yields a robust and enduring insulation material known for its incredible thermal performance.

At QPOD, we’re always looking to prioritise sustainability, and XPS underscores our commitment to eco-conscious solutions. As a resilient and energy-efficient option, XPS insulation not only enhances the thermal efficiency of structures but also minimises environmental impact, with no nasty poly-bead fly away as offered by EPS.  Its versatility also extends to a range of building insulation applications beyond foundations including walls, roofs, and floors, making it an ideal choice for projects striving for sustainability and energy efficiency.

EPS: Extruded Polystyrene Sheet


EPS, commonly employed in foundations, presents a pressing environmental issue, particularly due to poly bead flyaway. This occurs as EPS beads disperse across building sites, eventually finding their way into our waterways and green spaces. The lightweight nature of EPS, coupled with its open-cell structure, makes it a messy material to work with, and facilitates poly bead flyway.

Most noticeably, once in streams, these beads not only disrupt aquatic habitats but also endanger marine life when they reach the ocean. Moreover, the persistence of EPS beads in the environment exacerbates the problem, as they are non-biodegradable and can take hundreds of years to break down.

At QPOD, we recognise the severity of this issue and are committed to combating the environmental impact of EPS.

Why We Recommend XPS

With a distinct contrast between XPS and EPS established, let’s delve into why we recommend XPS. Our recommendation for XPS stems from a few key factors:

strength xps

Outstanding Strength and Durability

XPS insulation is remarkably strong and durable. Crafted through a meticulous extrusion process, XPS forms a closed-cell structure that gives it an unparalleled rigidity and resilience. This structural integrity allows XPS to withstand higher levels of compressive strength, distinguishing it as the preferred option for applications demanding robust load-bearing capabilities.

Enhanced Moisture Resistance

A standout characteristic of XPS insulation lies in its enhanced resistance to moisture infiltration. The closed-cell configuration of XPS effectively bars water absorption, guaranteeing sustained thermal efficiency even in moist or humid environments. Conversely, while EPS insulation provides commendable moisture resistance, prolonged exposure may render it vulnerable to water absorption over time.

xps thermal performance

Thermal Performance

XPS insulation consistently delivers dependable thermal efficiency over its lifespan. Its closed-cell structure and dense composition enable it to maintain insulation properties without notable thermal drift. This performance ensures sustained energy efficiency throughout the building’s life. In contrast, EPS insulation, with its more open-cell structure, may encounter some thermal variation over time.

Environmental Considerations

At QPOD, transparency is paramount to our values. While both XPS and EPS are recyclable materials, it’s crucial to consider their environmental implications. The manufacturing process and properties of XPS indeed result in a higher embodied energy compared to EPS. However, XPS stands out for its long-term durability, mitigating its higher initial energy footprint by offering an extended  life. This durability aspect also contributes to a reduced risk of polybead flyaway, further aligning with our commitment to environmental stewardship.

xps environmental considerations

Summary and More Resources

In conclusion, while both XPS and EPS have cemented themselves as having strong insulation properties in the use of underslab insulation, XPS emerges as the standout choice for its superior strength, moisture resistance, consistent thermal performance, and excellent compressive strength. These attributes make XPS a the preferred option for applications requiring durability, load-bearing capacity, and long-term insulation effectiveness.

When evaluating your insulation requirements, it’s essential to consider the specific demands of your project for an informed decision. And we’re here to help, so if you have a question please feel free to reach out and let us know below.

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