When to use this system
A termPIR® AL board beneath the floor finish is the default choice for new ground-bearing floors in single-family houses and ground floor levels:
- The WT 2021 requirement for ground-bearing floors is U ≤ 0.30 W/m²·K — already met with 70 mm. For modern energy-efficient standards (U ≤ 0.15), 140 mm of termPIR® AL is sufficient vs ~250 mm of EPS.
- The aluminium foil on top reflects the thermal radiation from the underfloor heating back towards the screed — increasing the efficiency of the heating system.
- Water resistance and load capacity — termPIR® does not deform under the weight of the screed and use, and is resistant to capillary moisture from the ground (water absorption < 2%).
Recommended variants
- termPIR® AL — default choice, aluminium foil on both sides, optimal thermal insulation performance.
- termPIR® AGRO P-REV — with aluminium reversed to the core (REV). Dedicated to underfloor heating and anhydrite screeds — the upper facing is resistant to alkalis from the screed.
Installation requirements
- PE film 0.2 mm as a capillary barrier — to be laid under the boards with a 15 cm overlap, sealed with tape.
- Board joints — sealed with aluminium tape to ensure full vapour tightness.
- Screed — C20/25 concrete (min. 8 cm for standard heating, 6.5 cm for anhydrite screed with heating).
- Edge zone (at walls) — a PES expansion tape around the entire perimeter prevents thermal bridges and screed cracking.
Technical documentation
termPIR® 2025 folder (Gór-Stal, 2025-04-23, pp. 14–15). Reaction to fire class E for the board itself; under the screed NRO (non-fire-propagating) in the final floor application.
Layer composition
| # | Layer | Thickness | λ | Role |
|---|---|---|---|---|
| 1 | Wooden flooring / porcelain tiles / floor covering | — | — | wearing layer |
| 2 | Concrete screed (with underfloor heating pipes) | — | — | screed / heating installation |
| 3 | Construction film | — | — | separating layer |
| 4 | termPIR® AL | 80–250 mm | 0,022 W/(m·K) | main thermal insulation |
| 5 | PE film min. 0.2 mm | — | — | capillary ground moisture barrier |
| 6 | Lean concrete | — | — | concrete sub-base |
| 7 | Waterproofing (if required by the design) | — | — | protection against groundwater |
| 8 | Mechanically stabilised aggregate | — | — | ground substructure |
U-value by insulation thickness
| termPIR® thickness | U [W/m²·K] | Meets WT 2021 (roof U ≤ 0.15) |
|---|---|---|
| 80 mm | 0,26 | — no |
| 100 mm | 0,21 | — no |
| 120 mm | 0,18 | — no |
| 150 mm | 0,14 | ✓ yes |
| 160 mm | 0,13 | ✓ yes |
| 180 mm | 0,12 | ✓ yes |
| 200 mm | 0,11 | ✓ yes |
| 220 mm | 0,10 | ✓ yes |
| 250 mm | 0,08 | ✓ yes |
Related catalogue items
Recommended variants
Installation accessories
