EPS vs PIR vs PU Insulation: A Panel Manufacturer’s Comparison

July 15, 2026

By Miku Zhang · Updated September 20, 2026

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

EPS vs PIR: Head-to-Head

Most of the questions we get from panel buyers are not “PU or PIR” — those two are close cousins made on the same foaming machine. The real fork is EPS vs PIR. Here is how they compare on the numbers that decide a panel spec.

Property	EPS (expanded polystyrene)	PIR (polyisocyanurate)
Typical declared λ	approx. 0.032–0.040 W/m·K, depending on grade and density	approx. 0.022–0.028 W/m·K, depending on facer and thickness
Core thickness for U = 0.20 W/m²·K (d = λ/U, calculated, not tested)	approx. 160–200 mm	approx. 110–140 mm
How the core is made	Beads pre-expanded with steam, moulded into blocks, cut, then laminated to facings with adhesive	Liquid polyol and isocyanate metered, mixed and reacted directly between the facings on a foaming line
Bond to steel facings	Needs a separate adhesive layer	Foam bonds to the facings as it reacts
Fire behaviour	Thermoplastic: softens and melts, needs a flame-retardant grade	Thermoset: chars rather than melts; generally the higher fire class in the same test
Service temperature	Softens above roughly 75–80°C	Stable well above 100°C
Material cost	Lowest of the three	Higher per m³, offset by thinner panels
Where it wins	Above-freezing rooms, warehouses, budget roof and wall panels, packaging	Cold rooms, freezers, fire-sensitive projects, anywhere panel thickness costs floor space

Two things the table does not show. First, the thickness gap compounds: a 50–80 mm thinner wall on all four sides of a cold room is usable floor area you get back for free. Second, the production side is different equipment. EPS panels come out of a bead pre-expander, a block mould and a cutting line plus a lamination step; PIR panels come out of a high-pressure foaming machine that reacts the core in place. If you are choosing a core, you are also choosing a factory.

Declared λ values are what manufacturers publish under the product standards EN 13163 (EPS) and EN 13165 (PIR/PUR), measured by test methods such as ASTM C518 or EN 12667. For background on EPS grades and testing, see the EPS Industry Alliance. Always check the declared value on the specific product datasheet rather than a generic figure.

When EPS Is the Right Choice

We sell PU and PIR foaming lines, so it would be easy to tell you EPS never wins. That is not true. EPS is the sensible core when: the room runs above freezing and the energy bill is not the dominant cost; wall thickness does not matter (a warehouse, not a blast freezer); the project is cost-capped and a thicker panel is acceptable; or the panel is a temporary or low-fire-risk structure. In those cases the extra 50–80 mm of thickness buys nothing, and EPS at the lowest cost per m² is the right call. Where the room goes below zero, where floor space is sold by the square metre, or where the fire class is specified, the argument flips to PIR.

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.

Choosing PIR over PU on the same panel line comes down to three machine settings: metering accuracy on the polyol/isocyanate ratio (PIR runs a higher isocyanate index), output rate in kg/min matched to your panel line speed, and tight component temperature control, since PIR’s faster reaction is less forgiving of drift. The blowing agent is typically cyclopentane on both chemistries; see our note on the cyclopentane high-pressure machine above for how that affects cell structure. A PU foam insulation core inside a household unit follows the same logic at smaller scale — see PU foam insulation inside a refrigerator cabinet.

FAQ

Is PIR better than PU for cold storage?

PIR has similar thermal conductivity to PU but better fire performance, so it is preferred where fire code is strict. For most cold rooms, PU offers the same insulation value at lower cost.

Why not use cheaper EPS for a cold room?

EPS has about 40% higher thermal conductivity and absorbs more moisture, so it needs thicker walls and degrades below 0°C. It suits budget or above-freezing rooms, not true cold storage.

Do you supply the insulation material?

No. We build the high-pressure foaming and sandwich-panel machines that produce PU and PIR cores. You run them with your own or sourced polyol and isocyanate system.

Can one machine make both PU and PIR panels?

Yes. PIR is a formulation adjustment of PU chemistry, so the same high-pressure foaming machine produces both by changing the formula and index.

Is PIR better than EPS?

For thermal performance per millimetre, fire behaviour and moisture, yes: PIR reaches the same U-value in a panel roughly 30–40% thinner than EPS. EPS is better on one axis only, material cost, which is why it still dominates above-freezing warehouses and budget wall panels.

How much thicker does an EPS panel need to be than a PIR panel?

Working from typical declared λ values (EPS approx. 0.032–0.040 W/m·K, PIR approx. 0.022–0.028 W/m·K), an EPS core needs roughly 1.4 to 1.6 times the thickness of a PIR core for the same U-value. Check the declared λ on the actual product datasheet; the ratio moves with grade and density.

Can the same factory make both EPS and PIR panels?

Not on the same line. EPS cores are made by steam pre-expansion, block moulding and cutting, then laminated to the facings with adhesive. PIR cores are reacted in place on a high-pressure foaming line that bonds directly to the facings. A factory that wants both needs two separate production lines.

Tell us your panel size, thickness and output — we will propose the right high-pressure foaming and panel line and quote.

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