Closed-cell polyurethane (PU/PIR) rigid foam typically reaches a thermal conductivity of 0.018-0.024 W/m·K at a core density of 38-45 kg/m³, while expanded polystyrene (EPS) sits at 0.030-0.038 W/m·K and 15-25 kg/m³ — a roughly 30-40% lambda gap that translates directly into wall-thickness savings for the same U-value [S1][S5].
Both are mainstream commodity insulation boards supplied from Chinese clusters in 2026, with the OKorder catalog listing PU sandwich panels at a minimum order of 500 m² and a supply capability around 100,000 m²/month, indicating the scale at which both materials are routinely traded [S2]. For a deeper cross-check on the EPS side, the EPS Board Price and Cost Guide 2026 breaks out density tiers and bodyboard-blank variants separately from construction-grade foam.
Lambda, Density and Closed-Cell Structure: Why the Numbers Diverge
PU/PIR is a thermoset, closed-cell foam blown with pentane or HFOs; the closed-cell ratio exceeds 90%, gas trapped inside the cells is a poorer conductor than air, which is why its declared lambda is consistently under 0.024 W/m·K and most PIR grades sit at 0.020-0.022 W/m·K [S1][S5]. EPS is a thermoplastic bead foam: pre-expanded polystyrene beads are steam-fused in a mould, the resulting closed-cell content is high but the polymer matrix itself is a poorer insulator, so the typical 0.030-0.038 W/m·K band holds regardless of brand [S3].
Density reinforces that gap. PU rigid foam marketed for construction commonly runs 38-45 kg/m³ as a structural working range; lower densities (30-35 kg/m³) are used for spray-applied PU and lose some lambda performance [S1]. EPS construction boards span 15-25 kg/m³ — the popular EPS 100 grade implies roughly 15-18 kg/m³ minimum, with heavier EPS 200 reaching ~25 kg/m³ when higher compressive strength is required [S3].
Fire Behaviour, Smoke and Code Acceptance
Fire-performance certification chains such as CE marking, ISO 9001:2008 quality systems, ISO 14001:2004 environmental systems and ISO 14024:1999 China Environmental Labelling are listed on PIR insulation board datasheets supplied by major Chinese vendors [S5].
EPS is an organic foam and requires flame-retardant additive modification to meet most construction codes; unmodified EPS is not acceptable behind facades in most jurisdictions. Polypro-type EPS insulation foam boards (a branded wall-siding integrated system) are explicitly advertised as fireproof, self-cleaning, anti-cold and high-strength, indicating that engineered EPS panels with treatment can compete in the integrated cladding market [S4]. For buyers who also handle cast-in-place concrete or release-agent spec lines, the chemistry contrast with release-agent vs admixture functions is a useful reminder that organic foams and chemical admixtures sit on different specification tracks.
Compressive Strength, Water Uptake and Dimensional Stability
Compressive strength at 10% deformation is the typical selection metric: PU/PIR rigid foam boards sit at ~150-220 kPa for the 38-45 kg/m³ band, sufficient for most low-slope roof and cavity-wall applications. EPS is graded by nominal density and compressive class: EPS 100 implies ≥100 kPa at 10% deformation, EPS 150 implies ≥150 kPa, EPS 200 implies ≥200 kPa — the same Aladdin-listed product line that frames the 15-25 kg/m³ density band [S3].
Water vapour and liquid water behave differently. PU's closed-cell structure yields water absorption below 1-2% by volume after 24 h immersion for most construction grades; EPS is more hydrophilic and can show 2-4% absorption on unprotected edges. Dimensional stability under heat favours PIR: typical service ceilings reach 110-120 °C short-term, while EPS softens near 80 °C and continuous service is capped around 70-75 °C, so EPS is unsuitable for hot-roof or industrial process lines.
Application Mapping: Where Each Material Earns Its Slot
Use PU/PIR for thin-section, high-R-value applications where wall thickness is constrained: flat-roof tapered insulation, cold-store sandwich panels (typically 100-200 mm PU core with steel facers), and pre-insulated ductwork where 0.020 W/m·K lambda lets the same R-value fit into roughly two-thirds the thickness of EPS [S2][S5].
Use EPS for budget wall-cavity fill, EIFS (external insulation finish systems) on low-rise buildings, and any project where the 30-40% lambda disadvantage is offset by raw material cost. For engineered wall-siding integrated systems, Polypro-type EPS panels deliver a self-cleaning, fireproof, anti-cold facade in a single composite layer [S4]. The Chinese-manufacturer showcase from Keda explicitly markets PU composite board for waterproofing-and-insulation integrated applications, including roof and below-grade use where the closed-cell water resistance is critical [S1].
Cost Levers, MOQ and Sourcing Bands
OKorder's PU insulation board listings show a minimum order of 500 m² with a supply capability around 100,000 m²/month — the kind of scale that places PU sandwich panels in the same commodity-buying category as engineered EPS cladding [S2][S4]. PIR graphite-enhanced boards from Beipeng carry a high-tech-enterprise-issued certificate chain and target premium cold-store and facade projects where lambda under 0.022 W/m·K justifies a price premium over standard PIR [S5].
On the EPS side, the Aladdin EPS 100 product line is sold as a "durable insulation solution" with the same density/grade framework that domestic Chinese distributors and export-trading platforms share [S3]. The cost lever is straightforward: EPS raw-material (polystyrene) is roughly half the per-kg cost of PU polyol-isocyanate systems, so EPS wins on absolute material cost, while PU wins on R-value-per-dollar where wall thickness has a price. For a related read on commodity-spec buying logic, the Block & Brick Buying Guide 2026 walks through a similar density-versus-tier framework for masonry.
Comparison Matrix: PU/PIR vs EPS on Four Decision Criteria
The four criteria most buyers care about: lambda (W/m·K), density (kg/m³), 10%-compression strength (kPa), and continuous service temperature (°C). PU/PIR: 0.020-0.024, 38-45, 150-220, 110-120. EPS: 0.030-0.038, 15-25, 100-200 (EPS 100/150/200 grade), 70-75. PU wins on thermal and temperature; EPS wins on raw material cost and ease of cutting on site; both are competitive on compression in their respective working density bands [S1][S3][S5].
The China-side sourcing reality: PU composite-board, sandwich-panel and PIR-grade manufacturers are concentrated in coastal industrial clusters with CE/ISO 9001:2008/ISO 14001:2004/ISO 14024:1999 certification chains [S5]; EPS board makers, including Polypro-style wall-siding integrated systems, run at lower capex and dominate the small-builder and export-trading channels [S3][S4]. For a related process-engineering comparison, the Self-Priming vs Sludge Pump piece follows the same spec-bands + sourcing-reality structure for a different equipment class.
For encyclopedic reference on the polymer side, the polyurethane insulation entry covers the broader chemistry, while EPS board and XPS board sit adjacent on the foam-insulation spectrum.