U-value Calculator

Calculate the heat transfer coefficient U for any layered building partition. Add layers from the materials library (BOKKA, competitors, structural materials) or enter your own lambda. Check compliance with Polish WT 2021. Everything calculated locally in your browser — no registration, no data transmitted.

Partition layers (from inside)

Tip: layer order from indoor (R_si) to outdoor (R_se). Reorder with ↑↓ arrows.

How to use?

  1. Select partition type — wall, roof, floor etc. You'll see the required U value per Polish WT 2021.
  2. Add layers in order from indoor. Each layer: pick a material from the library (BOKKA, EPS, mineral wool, concrete...) + enter thickness in mm.
  3. Custom material — for a product outside the library, enter name and λ manually.
  4. Check result in the right column — U, total R, total thickness, WT 2021 status.

🔄 EPS / Mineral Wool → PIR Conversion

30 cm of EPS in your project? Check what it would be in termPIR AL / WS / AGRO AL. Thickness savings and λ comparison.

📚 Ready BOKKA systems

25 designed systems with layer details, U-value and fire rating — ready for project specification.