PIR or EPS roof cores: how to compare sandwich panels

Here, the products have outer and inner metal facings with PIR or EPS between them. This is not a comparison between polystyrene below bituminous roofing and PIR foam alone. Such roofs would have different layers and installation methods.

Select two finished roof panels, one EPS and one PIR, and compare their properties in comparable configurations. Do not assume identical load capacity or joint design. Similar-looking steel facings do not mean the panels can be substituted without checking.

Compare PWS-D (EPS) and PWPIR-D (PIR) figures from the 2026 catalogue: the 100 mm EPS panel has a Uc-value of 0.37 W/(m²·K), while the 100 mm PIR panel has 0.21. In this comparison, PIR limits heat transfer more effectively. The figures concern these specific variants, not every panel with that core. Ordering requires data for the selected panels.

A lower panel U-value does not mean the same percentage reduction in heating bills. Heat losses also involve walls, windows, doors and ventilation. Temperature and operating hours matter. Panel data compare one part of the envelope; energy costs require a whole-building calculation.

In a second example, 200 mm EPS has a Uc-value of 0.19 W/(m²·K), while 120 mm PIR has 0.18. These values are close, though not identical. This compares solutions with similar insulation performance. Prices for equal-thickness panels do not always show which roof meets the requirement at lower cost.

If the target is a U-value no greater than 0.15 W/(m²·K), find an actually available variant achieving it. An example PIR panel may reach this at 145 mm. Do not calculate an EPS thickness by a simple conversion and assume it exists. Check the available range and declared data. A result for a hypothetical panel does not establish that it can be ordered and used.

Suppose 100 mm panels with 0.5/0.5 mm facings weigh 9.9 kg/m² for EPS and 12.6 kg/m² for PIR. These are figures for example configurations, not complete roofs. The lighter panel does not necessarily insulate better. Compare weight and U-value separately. Structural calculations must include the other loads too.

Lower weight can benefit transport or refurbishment, but it does not establish permissible support spacing. This depends on the interaction of core and facings and the load conditions. Do not infer capacity from foam density alone. The design must account for snow, wind, fixings and the structure supporting the panel.

Reaction to fire, fire resistance and roof performance under external fire exposure are different properties. They are not interchangeable. An example reaction-to-fire class B-s1,d0 does not specify minutes of fire resistance for the complete building element. The relevant assembly classification, including support, fixing and application conditions, is required.

Likewise, Broof(t1) concerns external fire exposure. It does not automatically confirm the same REI fire resistance as another roof. Compare requirements with the full performance of the selected solution. The name EPS or PIR alone does not establish fire-resistance minutes, and classifications must not be transferred between different panel assemblies.

Check the required pitch, laps and roof penetrations. Specify the cutback direction and panel lengths. Do not buy an EPS model as a PIR substitute without checking flashing and joint compatibility.

Review junction details and installation requirements for the selected panels. In agricultural or humid environments, choose suitable coatings too. Protective layers and fasteners matter regardless of core material. Damaged sheet or a leaking joint can undermine good thermal performance. A sound comparison therefore includes these components, their durability and their cost.

Only once both options meet the requirements. Then compare complete delivery and installation rather than a single price per m². Include flashings, fixings, transport and any support alterations. Check minimum production quantities and lead time.

There is no basis for a fixed PIR–EPS price difference without current quotations. Delivery terms can strongly influence small orders. PIR is a logical option where thermal performance at limited thickness matters. Consider EPS where the available model meets all design objectives and the complete solution is competitively priced.

Before choosing, check whether the offer concerns new production or warehouse stock. Available lengths and colours may limit the options. Material left from another order needs the same technical assessment as newly produced material. A favourable price does not change its properties or application limits.

Not in this example: the respective values are 0.37 and 0.21 W/(m²·K). Check the properties of the specific variants being purchased.

A lower U-value reduces heat flow, but operating costs depend on the entire building and how it is used.