Which Is Better, PIR or PUR? A Technical Comparison of PIR and PUR Sandwich Panels
When selecting insulated metal panels for warehouses, factories, cold storage facilities or commercial buildings, buyers often ask: which is better, PIR or PUR? Both materials provide thermal insulation, but their chemical structures, fire performance and product specifications can differ.
For buyers comparing a PIR Sandwich Panel with a PUR sandwich panel, the decision should be based on measurable performance rather than general claims. Core density, thermal conductivity, panel thickness, U-value, steel facing thickness, mechanical strength and fire classification all influence the suitability of a panel for a particular project.
ASTM International publishes test methods used to evaluate thermal insulation materials and sandwich construction performance. Understanding the relevant standards helps buyers compare technical data sheets and request appropriate test reports from suppliers.
1. What Is the Difference Between PIR and PUR?
PIR stands for polyisocyanurate, while PUR stands for polyurethane. Both are rigid foam insulation materials commonly used between two metal facings to manufacture insulated sandwich panels.
A PIR Sandwich Panel uses a polyisocyanurate foam core designed to provide thermal insulation and, depending on the product formulation and tested assembly, improved fire performance compared with some conventional polyurethane products.
PUR sandwich panels use a polyurethane foam core and are also widely used in industrial buildings, workshops, warehouses and other insulated structures. Their suitability depends on the declared thermal properties, fire classification and structural requirements of the intended application.
Neither material should be judged by its name alone. Buyers should compare the actual panel specifications and supporting test reports.
For example, ASTM C518, the Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus, can be used to measure the thermal transmission properties of insulation specimens. The results can help buyers compare insulation materials when testing conditions and specimen characteristics are comparable.
2. PIR vs PUR: Technical Specification Comparison
The following table presents published reference specifications from a manufacturer offering both PIR and PUR sandwich panels. These figures are product-specific and should not be treated as universal values or as confirmed specifications for every supplier.
| Technical Parameter | PIR Sandwich Panel | PUR Sandwich Panel |
|---|---|---|
| Insulation core | Polyisocyanurate | Polyurethane |
| Published core density | 40–42 kg/m³ | 38–42 kg/m³ |
| Published core thermal conductivity | 0.022 W/(m·K) | 0.022 W/(m·K) |
| Available core thicknesses | 30, 40, 50, 60, 75, 100, 125, 150 mm | 30, 40, 50, 60, 75, 100, 125, 150 mm |
| Published metal facing thickness options | 0.30, 0.35, 0.40, 0.50, 0.75, 1.00, 1.50 mm | 0.30, 0.35, 0.40, 0.50, 0.75, 1.00, 1.50 mm |
| Effective cover width | 1,000 mm | 1,000 mm |
| Published panel length range | 1–14 m | 1–14 m |
| Published minimum core compressive strength | ≥0.095 MPa | ≥0.095 MPa |
| Published reaction-to-fire classification | A-s1,d0 | B-s2,d0 |
| Published U-value at 40 mm | 0.497 W/(m²·K) | 0.497 W/(m²·K) |
| Published U-value at 150 mm | 0.143 W/(m²·K) | 0.143 W/(m²·K) |
Reference data: Zinc Cool's published PIR and PUR product specifications. Fire classifications, dimensions and thermal values apply to the specific products declared by that manufacturer.
The comparison shows that the two reference products have the same published thermal conductivity of 0.022 W/(m·K). Their published U-values are also identical at the two listed thicknesses.
This demonstrates why it is inaccurate to claim that every PIR Sandwich Panel provides better thermal insulation than every PUR panel. Actual performance depends on the product construction, insulation thickness, facings, joints and test conditions.
For procurement, ask suppliers to identify the applicable test method for each declared property. For thermal conductivity, ASTM C518 is a useful standard to check when reviewing the supporting documentation.
3. Thermal Performance: How Do Thickness and U-Value Affect Insulation?
Thermal conductivity, represented by λ, measures how readily heat passes through a material. A lower value generally indicates better insulation performance for the material itself.
U-value describes the rate of heat transfer through a complete building component under specified conditions. A lower U-value indicates better thermal insulation performance for that component.
The reference manufacturer publishes the following U-values for its PIR and PUR panels:
| Panel Core Thickness | Published U-Value |
|---|---|
| 40 mm | 0.497 W/(m²·K) |
| 150 mm | 0.143 W/(m²·K) |
The 150 mm reference panel has a substantially lower U-value than the 40 mm panel. This illustrates the effect that increased insulation thickness can have on thermal performance.
However, these two values should not be used to calculate exact U-values for intermediate thicknesses. Buyers should obtain the manufacturer's declared value for the specific panel being quoted.
When evaluating a PIR Sandwich Panel, ask whether the reported thermal conductivity was measured using ASTM C518 or another specified method. Also confirm whether the quoted U-value represents the complete panel assembly or a calculated value based on particular assumptions.
These distinctions are important when comparing quotations for cold storage, temperature-controlled production areas and energy-efficient industrial buildings.
4. Fire Performance: Which Test Standards Should Buyers Check?
Fire performance is a major consideration when selecting insulated metal panels. PIR and PUR formulations can differ in reaction-to-fire performance, but the actual classification must be verified for the specific product.
In the reference manufacturer's data, the PIR panel is classified A-s1,d0 and the PUR panel B-s2,d0 under EN 13501-1. These are European reaction-to-fire classifications, not ASTM classifications.
For projects using ASTM-based specifications, buyers may encounter ASTM E84, the Standard Test Method for Surface Burning Characteristics of Building Materials.
ASTM E84 measures and reports flame spread and smoke developed indices under specified test conditions. It is not interchangeable with EN 13501-1, and its results do not by themselves establish that a material is noncombustible or determine the fire-resistance rating of a complete wall or roof assembly.
Therefore, when purchasing a PIR Sandwich Panel for a factory, warehouse or commercial building, confirm the exact fire standard required by the project. Request the relevant test report and verify that the tested construction matches the proposed product.
If the building specification requires a fire-resistance duration, such as a specified number of minutes, a separate fire-resistance assessment for the applicable assembly may be necessary. Do not rely solely on the foam type or a surface-burning result.
5. Panel Thickness, Steel Facing and Mechanical Performance
Insulation thickness is only one part of the product specification. Steel facings, profile geometry, panel joints and support spacing all affect the final panel's suitability.
The reference product range offers core thicknesses from 30 mm to 150 mm and metal facing thickness options from 0.30 mm to 1.50 mm. These are the published options of that manufacturer, not a guarantee that every supplier offers the same range.
Steel facing thickness should be specified clearly. Buyers should also confirm whether the quoted figure refers to base metal thickness or total coated thickness, and identify the steel grade, coating and paint system.
Mechanical performance matters as well. The reference PIR and PUR products declare a minimum core compressive strength of 0.095 MPa. Buyers should confirm the test method, specimen preparation and reporting conditions behind this value before using it for engineering decisions.
For sandwich constructions, several ASTM standards may be relevant:
ASTM C365/C365M addresses flatwise compressive properties of sandwich cores.
ASTM C273/C273M addresses shear properties of sandwich core materials.
ASTM C393/C393M addresses flexural properties of sandwich constructions.
These standards examine different mechanical properties. They should not be treated as interchangeable, and a test result for a bare core does not automatically establish the structural capacity of a complete insulated panel.
When specifying a PIR Sandwich Panel for a roof or wall, ask for the relevant load tables, allowable support spans, design loads and test reports. The appropriate panel depends on the thickness, profile, facing material, span and installation conditions.
6. Panel Weight and Thermal Performance by Thickness
To illustrate how specifications vary between products, the following table presents published data for a separate PIR wall panel manufactured by Paneltech.
| PIR Core Thickness | Published Panel Weight | Published U-Value |
|---|---|---|
| 40 mm | 9.9 kg/m² | 0.58 W/(m²·K) |
| 60 mm | 10.7 kg/m² | 0.37 W/(m²·K) |
| 80 mm | 11.5 kg/m² | 0.27 W/(m²·K) |
| 100 mm | 12.3 kg/m² | 0.22 W/(m²·K) |
| 120 mm | 13.1 kg/m² | 0.18 W/(m²·K) |
Reference: Paneltech PWPIR-S wall panel technical data. These values apply to that particular product design and should not be transferred directly to other manufacturers' panels.
The table shows that, within this product range, the published panel weight increases from 9.9 kg/m² at 40 mm to 13.1 kg/m² at 120 mm, while the U-value decreases from 0.58 to 0.18 W/(m²·K).
This information can help project teams assess the relationship between panel thickness, weight and insulation performance. However, panel weights and U-values vary by manufacturer, facing thickness, profile and construction.
For a meaningful quotation comparison, request a product-specific data sheet rather than relying on general market averages.
7. Which Is More Cost-Effective: PIR or PUR?
The most cost-effective choice depends on the required technical performance, local building regulations, project budget and installation conditions.
A PUR panel may be suitable when its verified insulation performance and fire classification meet the project requirements at a competitive price. A PIR Sandwich Panel may be the better choice when the specific product's documented performance better matches the building specification.
Buyers should compare quotations based on equivalent configurations, including:
Core material and thickness.
Core density and thermal conductivity.
U-value at the specified thickness.
Outer and inner steel facing thicknesses.
Steel grade, coating and paint system.
Effective cover width, panel length and profile.
Fire classification and supporting test reports.
Mechanical properties and applicable load tables.
Delivery, installation accessories and warranty conditions.
ASTM test methods can help standardize the measurement of selected material or panel properties. Nevertheless, the use of an ASTM test method does not mean that the product is automatically ASTM-certified or that it meets every building-code requirement.
The supplier should provide the actual test report, identify the tested product and confirm whether the test configuration matches the proposed panel.
8. PIR or PUR: Which Should You Choose?
There is no single answer for every project. The right choice is the panel that meets the project's thermal, fire, mechanical and regulatory requirements at an acceptable overall cost.
Choose a PIR Sandwich Panel when the specific product's verified thermal performance, fire classification and construction meet the project specification. Consider PUR when its documented properties satisfy the same requirements and its cost or availability offers an advantage.
Before placing an order, request a technical data sheet covering core density, thermal conductivity, U-values by thickness, steel facing thicknesses, panel weight and fire classification. Where ASTM-based testing is required, ask which ASTM test methods were used and obtain the corresponding reports.
The bottom line: PIR and PUR should be compared using product-specific numerical data and verified test results. Reviewing the relevant ASTM standards alongside the manufacturer's technical documentation helps buyers make a more informed decision when sourcing insulated metal sandwich panels.
