Why Polyurethane (PU) outperforms traditional insulation materials: (A Comprehensive Comparison)
Roof insulation: Why does Polyurethane (PU) outperform traditional insulation? (Complete Comparison)
During a renovation or construction project, the roof accounts for up to 30% of a building's heat loss. Choosing the right insulation is therefore strategic, both for thermal comfort and for the longevity of the structure. But faced with the multitude of materials available—mineral wools, polystyrene, bio-sourced materials—how do you make the right technical choice?
As roofing experts, we have observed that one material stands out clearly for demanding projects: polyurethane (PU). Integrated into the heart of our Isotuiles sandwich panels, it is revolutionizing roof renovation. Here is our complete technical comparison between polyurethane and other insulation solutions on the market.
1. Polyurethane (PU) VS Mineral wools (Glass and Rock)
Historically very common on the market, glass wool and rock wool are often chosen for their low initial cost. However, they have major technical limitations in the long term for roofing.
Mineral Wools
- Thickness: Requires very high thickness (often > 25 cm) for a good R-value.
- Longevity: Risk of settling over the years, creating thermal bridges.
- Humidity: Very sensitive to water; they lose their insulating properties if they get wet.
The Polyurethane (PU) Advantage
- Thermal conductivity (Lambda): Market leader (approx. 0.022 W/m.K). Insulates better with half the thickness.
- Stability: Rigid closed-cell foam; no settling possible.
- Watertightness: Rot-proof and completely insensitive to humidity.
2. Polyurethane VS Polystyrene (EPS & XPS)
Expanded polystyrene (EPS) and extruded polystyrene (XPS) are cellular plastic insulators, from the same "family" as PU. They are lightweight and rigid, but polyurethane maintains a lead for structural roofing applications.
Polystyrene (EPS / XPS)
- Performance: Good insulating power, but lower than PU (Lambda around 0.030 to 0.038).
- Thermal resistance: Increased sensitivity to extreme heat under the roof (risk of deformation for standard EPS).
The Polyurethane (PU) Advantage
- Absolute performance: At equal thickness, PU offers 30% to 40% higher thermal resistance (R) than EPS.
- Structural adhesion: The PU is injected directly between the steel facings of our sandwich panels, ensuring exceptional cohesion and rigidity of the steel deck.
3. Polyurethane VS Bio-sourced insulators (Wood fiber & Cellulose wadding)
Natural insulators are appealing for their thermal phase shift (summer comfort). However, their implementation in roofing is complex and demanding for the building's structure.
Bio-sourced (Wood, Wadding)
- Weight: Very dense and heavy materials (up to 50 kg/m³ for wood fiber). The framework often needs to be reinforced.
- Implementation: Requires multiple layers (vapor barrier, under-roof screen, sheathing, counter-battening).
The Polyurethane (PU) Advantage
- Ultra-lightweight: An Isotuiles panel weighs a tenth of the weight of a traditional roof insulated with wood + tiles. Ideal for not overloading an old framework.
- Direct installation on framework: No multiplication of layers. The panel integrates the underside, insulation, and waterproof covering into a single element.
The Isotuiles solution: The benefits of the PU sandwich panel
By choosing Isotuiles panels that incorporate a high-density polyurethane foam core, you are opting for performance without compromise:
- Zero thermal bridges: Thanks to a millimeter-precision interlocking system and a detailed layout established by our design offices, insulation is continuous.
- Speed of execution: Installation is up to 3 times faster than a traditional method. Insulation and waterproofing are done in a single operation.
- Expert adaptability: Our panels are easy to install, even with a minimal slope, where traditional tiles reach their limits in terms of watertightness.
- Longevity: The combination of profiled steel (tile aesthetic) and PU guarantees a robust roof, without heavy maintenance, for decades.
The verdict for your roof
While glass wool remains an entry-level solution for non-converted attics, polyurethane stands out as the premium material for exterior roof insulation (sarking or sandwich panels). It allows you to preserve interior volumes, lighten your building's structure, and ensure perfect watertightness.
