PUR vs EPS: which thermal insulation to choose

Choose one thermal insulation under screed is not a technical detail. It is a decision that directly impacts the thermal comfort, the energy performances of the building and the efficiency of heating, especially when a underfloor heating is planned.

Among the most used solutions in Belgium, two options are always used: polyurethane foam (PUR) projected and the EPS pellets.
Although their objective is the same (to limit heat loss), their operation, their implementation and their performances differ greatly.

In this article, we compare PUR vs EPS under screed to help you choose the most suitable solution for your project.

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Why insulate under a screed?

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The screed is not insulating in itself. Sans thermal insulation under screed, a large part of the heat produced escapes downwards, in particular on a full slab or on a ventilated vacuum.

Good insulation allows:

• to limit the heat losses,
• to improve the comfort on the ground (less sensation of cold),
• to optimize the performance of a underfloor heating,
• to reduce the overall energy consumption of the building.

The choice of insulating material is therefore strategic.

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Understanding the two thermal insulation solutions under screed

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PUR insulation projected under screed

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La polyurethane foam (PUR) is projected directly onto the slab in liquid form. It expands rapidly, hardens and forms a continuous, seamless insulating layer.

Main characteristics:

• Excellent thermal performance
• Very low thickness required
• Continuous insulation, without thermal bridges
• Fast implementation by projection

La PUR under screed is widely used in renovation, when the available height is limited.

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EPS insulation under screed (pellets)

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THEEPS under screed consists of expanded polystyrene beads mixed with a binder. The mixture is spread and then leveled before installing the screed.

Main characteristics:

• Good thermal insulation
• Lighter solution
• Adapted to irregular surfaces
• Good stability when properly implemented

Les EPS pellets are often used when you want to catch up on levels or fill in volumes.

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Comparative PUR vs EPS under screed

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Thermal performance

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La Projected PUR offers superior thermal performance with equal thickness. It makes it possible to achieve a high level of insulation with fewer centimeters, which is a major advantage in renovation.

THEEPS under screed insulates properly, but generally requires a greater thickness to obtain an equivalent result.

👉 Advantage: PURE

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Thickness available

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• PUR under screed : ideal when height is limited
• EPS under screed : requires more thickness for equivalent insulation

👉 Advantage: PURE

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Adaptation to the support

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THEEPS pellets adapts very well to irregular supports. It makes it possible to make up for differences in level before screed.

La Projected PUR fits the existing surface perfectly, but requires a clean and well-prepared support.

👉 Advantage: PES on complex supports

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Speed of implementation

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La Projected PUR is extremely quick to install. Once hardened, the screed can be quickly installed.

Les EPS pellets require more time to set up and stabilize before screed.

👉 Advantage: PURE

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Compatible with underfloor heating

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Both solutions are compatible with a underfloor heating, but the PUR under screed allows better heat transmission to the top thanks to its more efficient insulation.

👉 Advantage: PURE

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When should you choose PUR foam under screed?

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La polyurethane foam (PUR) is particularly recommended if:

• The Available height is limited,
• You want a maximum thermal insulation,
• You are installing a underfloor heating,
• You are in renovation,
• you want to limit thermal bridges.

It is a very efficient solution, provided it is implemented by an experienced professional.

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When should EPS pellets be preferred under screed?

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Les EPS pellets are a good option if:

• The support is rugged,
• It is necessary Catch up levels,
• the available thickness is not a major constraint,
• the project requires a more flexible solution for adapting to the medium.

They provide reliable insulation, provided that the implementation is thorough.

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Common mistakes to avoid

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• Choose insulation only according to habit, without site analysis
• Overlook the available height before deciding
• Underestimating the impact of insulation on long-term comfort
• Entrust the installation to a non-specialized applicator

One poorly selected or improperly installed screed insulation may cancel out a large part of its profits.

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Conclusion: PUR or EPS under screed, the right choice depends on the project

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There is no one-size-fits-all solution.
La PUR projected under screed offers superior thermal performance and great efficiency on constrained construction sites.
Les EPS pellets remain a relevant alternative in specific configurations, especially when adaptation to the support is a priority.

Chez Davide Chape, each project is analyzed individually: existing support, available height, use of the building and type of heating. This approach makes it possible to choose the better thermal insulation under screed, without compromising on durability or comfort. Contact us now to get a quote.