Choosing the right insulation core is the single biggest decision in cold storage and cold-room construction. The three common options — rigid polyurethane (PU), polyisocyanurate (PIR) and expanded polystyrene (EPS) — differ sharply in thermal performance, fire behaviour, moisture resistance and cost. As a manufacturer of the high-pressure foaming and sandwich-panel machines that produce these cores, we compare them below to help you specify the right panel for your cold store.
Quick Comparison
| Property | PU (Polyurethane) | PIR (Polyisocyanurate) | EPS (Expanded Polystyrene) |
|---|---|---|---|
| Thermal conductivity (λ, W/m·K) | 0.022–0.024 | 0.022–0.023 | 0.033–0.038 |
| Wall thickness for same R-value | Thin | Thinnest | ~50% thicker |
| Fire performance | Good | Best (chars, low flame spread) | Poor (flammable unless FR-treated) |
| Moisture absorption | Low (closed-cell) | Low (closed-cell) | Higher |
| Low-temperature stability | Excellent | Excellent | Fair |
| Material cost | Medium | Medium-high | Lowest |
| Best for cold storage | Yes | Yes (fire-critical) | Budget / above-zero only |
Why PU and PIR Win for Cold Storage
PU and PIR are closed-cell rigid foams with a thermal conductivity around 0.022–0.024 W/m·K — roughly 40% lower than EPS. That means a PU/PIR panel reaches the same insulation value at a much thinner wall, saving internal volume and steel. Their closed-cell structure also absorbs very little moisture, which is critical below 0°C where water ingress and ice build-up destroy EPS performance over time.
PIR is essentially an upgraded PU chemistry with better fire performance — it chars rather than melts and has lower flame spread, so it is preferred where fire code is strict. EPS remains the budget choice for above-freezing rooms, but its higher λ and moisture uptake make it a poor fit for true cold storage.
How the Panels Are Made
PU and PIR cold-store panels are produced on a high-pressure PU foaming machine feeding a sandwich-panel production line. Accurate metering and a self-cleaning mixing head give uniform density and closed-cell content — the two factors that decide real-world λ. For refrigerator and freezer cabinets, the same chemistry is foamed with a cyclopentane high-pressure machine. See also why polyurethane is the future of the cold chain.
FAQ
Is PIR better than PU for cold storage?
Why not use cheaper EPS for a cold room?
Do you supply the insulation material?
Can one machine make both PU and PIR panels?
Tell us your panel size, thickness and output — we will propose the right high-pressure foaming and panel line and quote.