Practical guide
How to choose insulation thickness
Good insulation thickness is a compromise between thermal target, available space, and the rest of the construction. The calculator helps you compare options before you lock the design.
Thickness is not chosen in isolation. It depends on the target U-value, the material lambda, and the layer stack around it.
Thermal target
Start with the U-value you want to reach. That gives the thermal goal for the full assembly.
Material lambda
Lower lambda means you need less thickness for the same thermal resistance.
Available build-up
The available space, service layers, finishes, and structure often limit how thick the insulation can actually be.
If one board has a lambda of 0.035 and another has 0.022, the better board reaches the same resistance with less thickness. That does not automatically mean it is the best choice for every project.
Useful formula
d = R × lambda
Estimate thickness from target resistance, then compare it with the actual build-up limits.
Confirm the target U-value or R-value first.
Check whether the assembly can physically accept the thickness.
Verify junctions, edges, and openings before finalizing the number.
Compare the result against other materials if space is limited.
Continue with the calculator and guides
Calculator
Build the full assembly and check the U-value.
How to calculate U-value
Read the practical guide for lambda, R, and U.
R-value vs U-value
Compare layer resistance with whole-assembly performance.
Wall calculator
Check wall assemblies and insulation layers.