Target U-value
Floor intentHow much insulation for floor?
Floor insulation depends on whether the floor is on grade, over a void, or part of a heated structure. Use this page for a quick reference result.
Best for
- Floors
- Slabs over ground
- Suspended floors
How much insulation is needed to reach 0.20 W/m²K?
Use the same formula as the calculator: target resistance minus existing resistance, then convert to thickness with the insulation lambda.
Example build-up
Target U-value 0.20 W/m²K, existing floor resistance 1.20 m2K/W, insulation lambda 0.035 W/mK.
Result
Required insulation thickness is approximately 11.3 cm.
Why floor thickness can vary
Ground contact
Floors on ground can behave differently from suspended floors.
Service space
Pipes, services, and screeds can affect the available insulation depth.
Check the build-up
The structure and finish layers can contribute useful resistance before insulation is added.
Next steps
Insulation thickness calculator
Open the calculator for a custom floor or wall build-up.
Open calculator