Short answer
Choose PU or PIR when you need the best insulation for the thickness (cold rooms, warehouses). Choose rock wool when fire resistance is the priority (fire walls, escape routes, high-risk buildings). EPS is the budget, lightweight option for site offices and simple sheds, and glass wool suits roofs where sound absorption and non-combustibility are wanted.
Core comparison
| Core | Thermal conductivity (λ) | Fire behaviour | Best for |
|---|---|---|---|
| PU (polyurethane) | ≈ 0.022 W/m·K | Combustible; class depends on formulation | Cold rooms, warehouses, roofs |
| PIR (polyisocyanurate) | ≈ 0.022 W/m·K | Better than PU; chars rather than melts | Warehouses, cold stores with fire requirements |
| EPS (expanded polystyrene) | ≈ 0.037 W/m·K | Combustible; lowest fire performance | Site offices, labour camps, light sheds |
| Rock wool (mineral wool) | ≈ 0.042 W/m·K | Non-combustible; fire-rated walls possible | Fire walls, factories, public buildings |
| Glass wool | ≈ 0.041 W/m·K | Non-combustible | Roofs, acoustic walls |
λ values are typical figures from manufacturer data. Always check the datasheet and test reports of the exact panel supplied.
Insulation: what the numbers mean
The lower the λ value, the better the insulation. PU and PIR insulate about 1.7 – 1.9 times better than EPS, rock wool or glass wool of the same thickness. To match a 100 mm PU panel you need roughly 170 – 190 mm of mineral wool.
Fire: where mineral wool wins
Rock wool and glass wool do not burn. Rock wool panels can be tested as fire-resistant walls (for example to EN 1364 / EN 13501-2), which is why they are used for compartment walls and escape routes. In the UAE, the panel system used must meet the Civil Defence requirements for the building type, so ask for the approval and test reports before ordering.
Weight and handling
- EPS and PU / PIR panels are light and fast to install.
- Rock wool panels are noticeably heavier because of the core density, so purlins and handling need to allow for it.
- All cores come with the same steel skins and joint styles for walls and roofs.
Frequently asked questions
Which sandwich panel is fireproof?
No panel is fully fireproof, but rock wool panels are non-combustible and can achieve fire-resistance ratings as walls. They are the usual choice where fire rating is required.
Which panel is cheapest?
EPS panels are usually the lowest-cost option, followed by PU. Rock wool panels cost more because of the heavier core and fire testing.
Are sandwich panels load-bearing?
No. They span between purlins or girts on a steel frame and carry wind and roof loads only between supports.