Wall U-value target 0.40 - Lambda Calculator

At a glance

Assembly type

Brick wall

Base wall build-up used for the estimate.

Total thickness

34.9 cm

Remaining resistance is translated into insulation thickness.

Estimated U-value

0.40 W/m²K

Target U-value 0.40 W/m²K based on a brick wall reference build-up.

Worked example

How much insulation is needed to reach 0.40 W/m²K?

The retrofit example starts from the base wall resistance, subtracts it from the target total resistance, and converts the remaining resistance into thickness.

Layer	Material	Thickness	Lambda	R

Layer	Material	Thickness	Lambda	R
Interior finish	Gypsum plaster Interior finish	1.5 cm	0.700 W/mK	0.02 m²K/W
Solid ceramic brick	Solid ceramic brick Masonry wall leaf	25 cm	0.770 W/mK	0.32 m²K/W
External finish	Silicone render Facade finish	1.5 cm	0.870 W/mK	0.02 m²K/W
Mineral wool	Mineral wool General insulation	6.9 cm	0.035 W/mK	1.97 m²K/W
Surface resistances				0.17 m²K/W
Total resistance				2.50 m²K/W

How it is calculated

Target U-value calculation

R = d / lambda

The target resistance is 1 / U. Once the base wall resistance is known, the remaining resistance can be turned into thickness for a chosen insulation material.

U = 1 / (Rsi + sum(R layers) + Rse)

For this reference page, mineral wool and EPS are compared side by side so the page stays useful without being empty.

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Comparison

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Lambda Values Table

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Use the main calculator to edit layers, compare materials, and export a custom result.

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Insulation thickness calculator

Move from a U-value target to the thickness needed for walls, roofs, and floors.

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Notes

Target note

This is a quick reference page for planning. Use the full calculator to verify junctions and detailed layer ordering.

Thickness comparison

Mineral wool and EPS are shown because they are common search targets and give a fast comparison baseline.