Composite Caravan Construction: How XPS Foam Improves Insulation and Comfort

FIbreglass Skin with an XPS Core

Modern offroad caravans are expected to do more than survive rough tracks. They need to stay comfortable in harsh Australian conditions, from sun-baked outback afternoons to cold desert nights. One of the biggest contributors to that comfort is how well the caravan structure manages heat transfer.

Composite fibreglass panels with an XPS (extruded polystyrene) core have become the benchmark construction method for high-quality caravans because they address insulation at the structural level, not as an afterthought.

This article explains how these panels work, why they insulate so effectively, and what that means in real-world use.

Understanding Heat Transfer in a Caravan

Before looking at materials, it helps to understand how heat actually moves into and out of a caravan. There are three main mechanisms:

1. Conduction Heat travelling directly through solid materials. For example, the sun heating the outer wall and that heat moving inward.

2. Radiation Heat energy from the sun absorbed by surfaces, especially dark exterior finishes.

3. Convection Heat moving through air gaps or cavities, often occurring inside traditional framed walls.

In conventional caravan construction, timber or aluminium framing creates multiple thermal bridges. These bridges allow heat to bypass insulation and move directly through the structure.

Composite panels are designed to interrupt this process.

What Is a Composite Fibreglass Panel with XPS Core?

A composite panel typically consists of:

• An outer fibreglass skin

• A rigid XPS foam core

• An internal fibreglass or composite inner skin

These layers are bonded together under pressure to form a single structural panel. The result is a strong, lightweight, and highly insulated wall, roof, or floor panel.

Unlike framed construction, there are no repeating structural members transferring heat from outside to inside.

How XPS Foam Reduces Heat Transfer

The insulation performance largely comes from the XPS core itself.

Closed-Cell Structure

XPS foam is made up of millions of tiny closed cells filled with trapped gas. These cells dramatically slow heat movement because:

• Air and gas are poor conductors of heat.

• The closed-cell structure prevents air circulation within the panel.

• Heat energy cannot easily move from one side to the other.

This reduces conductive heat transfer significantly compared with timber or aluminium-framed walls.

Consistent Insulation Across the Entire Panel

Because the foam runs continuously through the panel:

• There are no gaps where insulation is missing.

• There are no cold or hot spots created by framing.

• The thermal performance remains consistent across the entire wall or roof.

This is particularly noticeable in extreme sun exposure where traditional framed walls can create warm strips where structural members sit.

Thermal Lag and Real-World Comfort

One often overlooked benefit of composite panels is thermal lag.

Thermal lag refers to how long it takes for outside temperature changes to affect the interior. XPS-core panels slow down this transfer, meaning:

• The interior heats up more slowly during the day.

• The interior loses heat more slowly at night.

In practical terms, this means the air conditioner or heater cycles less often and maintains temperature more easily.

For off-grid travel, this directly translates into lower power consumption.

Roof Performance: Where Insulation Matters Most

The roof experiences the highest solar load on a caravan. Under direct Australian sun, roof surface temperatures can exceed 60°C.

A composite roof panel with an XPS core:

• Reduces heat entering from above.

• Limits radiant heat transfer into the living space.

• Helps prevent the “radiant oven” effect common in poorly insulated vans.

This is why high-quality composite builds often feel noticeably cooler even before air conditioning is turned on.

Moisture Resistance and Long-Term Performance

Another advantage of XPS is that it does not readily absorb water. Unlike some insulation materials:

• Moisture does not significantly reduce its insulation value.

• The panel maintains structural integrity over time.

• There is less risk of mould or insulation breakdown.

Because the insulation is bonded within the panel, it cannot slump or shift with vibration or age.

Strength and Insulation Working Together

In composite construction, insulation is not simply inserted into a wall cavity. The XPS core is part of the structural system itself.

This delivers:

• High rigidity without heavy framing

• Reduced flex and movement

• Improved sealing against dust and water ingress

The result is a structure that is both stronger and thermally efficient.

The Real Benefit for Travellers

The outcome of all this engineering is simple:

• More stable internal temperatures

• Less reliance on air conditioning and heating

• Better comfort in extreme climates

• Improved energy efficiency when travelling off-grid

  
  

In remote touring conditions where power and water are valuable resources, insulation becomes more than comfort. It becomes part of the van’s overall capability.