They look identical. They perform very differently.
PU board, also known as polyurethane sandwich board, polyurethane composite board, or polyurethane energy-saving board, the correct term is building-use polyurethane insulation sandwich board. This product is a double-layer color steel plate, single-layer color steel plate, stainless steel, etc., with polyurethane hard foam as the insulation layer. It is usually used for the wall and roof enclosure systems of industrial plants, logistics warehouses, and modular houses.
PIR, also known as polyisocyanurate, is a foaming material produced by the reaction of isocyanate with polyether after catalytic action. Its physical and fire resistance properties are more superior than those of ordinary polyurethane. It is an ideal organic low-temperature insulation material with low thermal conductivity, light weight, shock resistance, and strong adaptability. It is widely used in oil refineries, chemical plants, ethylene, fertilizers, cold storage, and the construction industry for insulation and heat preservation.
The core difference: fire behavior
PU foam is a thermoplastic material. Under sustained high heat, it softens, melts, and releases dense smoke. Standard PU panels achieve B3 fire rating; with flame retardants added, they can reach B2. That's acceptable for many general warehouses and moderate-climate projects, but it fails stricter fire codes in Europe and the Middle East.
PIR is thermosetting. When exposed to flame, it forms a char layer that shields the underlying foam from heat and slows fire spread. PIR typically reaches B1 rating, with oxygen index above 35%. In a controlled furnace study, mass loss at 350°C was 29% for PIR versus 83% for PU-a dramatic gap in thermal stability.
Insulation and other trade-offs
On thermal performance, the two are close. PU conductivity is typically 0.022–0.026 W/mK; PIR is slightly better at 0.020–0.023 W/mK. For most warehouses, the difference is negligible. For a massive cold storage facility running 24/7, PIR's edge can add up over decades.
PIR also has higher compressive strength (density 45–55 kg/m³ vs. PU's 35–45) and better high-temperature stability-PU degrades above 100°C, while PIR tolerates up to 120°C or higher.
The trade-off? PIR costs 12–25% more than PU, and its foam is more brittle. Rough handling or improper cutting can cause internal cracking, which undermines insulation performance.
Which one should you buy?
Choose PU if your project is a general warehouse, ordinary factory enclosure, or cold storage with moderate fire requirements-and your local building code doesn't mandate B1. You'll get proven insulation at a lower cost.
Choose PIR if your project faces strict fire codes (especially in Europe or the Middle East), operates in a tropical high-temperature environment, or involves high-value cold-chain storage where fire risk is unacceptable. The upfront premium buys lower smoke emission, better high-temperature stability, and peace of mind.
One warning: many suppliers sell ordinary PU with flame retardants as "PIR." Real PIR requires genuine chemical modification with higher isocyanate content. Always demand a third-party fire test report before ordering.
