How much insulation for wall?

Walls are the most common use case for insulation planning. This page gives a direct reference result for a standard wall build-up.

Best for

Worked example

How much insulation is needed to reach 0.20 W/m²K?

This wall example uses a simple target-U method so the number can be checked quickly before moving to a full assembly calculation.

Example build-up

Target U-value 0.20 W/m²K, existing wall resistance 1.40 m2K/W, insulation lambda 0.035 W/mK.

Result

Required insulation thickness is approximately 11.5 cm.

Wall notes

Brick, concrete, and aerated concrete each start with a different base resistance.

Lower U-values need more insulation thickness unless the wall already has useful resistance.

Junctions, fixings, and finishes affect the final build-up even if the basic estimate looks right.

Open the calculator for a custom wall build-up.

See the wall-specific reference calculator.

Compare the same target-U method on a brick wall page.