Brick lambda: thermal conductivity and product data
Brick has no single universal lambda value. Wienerberger's UK English Red product page lists thermal conductivity 0.450 W/(m·K), with the stated EN 1745:2012 S1 basis and gross dry density 1700 kg/m³. This is a documented example for that product, not a default for every solid brick, hollow block or completed wall.
Find the value for your brick
Record the exact product, intended market, dimensions, density, document revision and the conditions attached to the thermal value. A fired-clay facing brick, a perforated clay block and a calcium-silicate unit are different products. Density and moisture matter; a number without its conditions is insufficient for a wall calculation.
Product conductivity and wall performance
Lambda describes conductivity in W/(m·K). A homogeneous layer has resistance R = thickness / lambda in m²·K/W, with thickness in metres. A complete masonry wall also contains mortar joints and possibly cavities, ties, finishes and insulation. Product conductivity alone is not the U-value of that assembly.
Worked layer example
Using 0.1025 m and 0.450 W/(m·K) as an illustrative homogeneous layer gives R = 0.1025 / 0.450 ≈ 0.228 m²·K/W. This arithmetic example does not certify the resistance of a bonded masonry wall or convert a dry product value to a design moisture condition.
Choose comparable data
Compare values with the same units and relevant measurement or design conditions. A lower lambda at equal thickness gives a higher layer resistance, but it says nothing by itself about compressive strength, moisture suitability, fire performance or acoustic performance. Obtain the appropriate current declaration and assembly method before specifying a wall.
Examples with stated assumptions
| Inputs and method | Result |
|---|---|
| English Red product example | λ = 0.450 W/(m·K) |
| Illustrative 102.5 mm homogeneous layer | R ≈ 0.228 m²·K/W |
Result scope
The UK product page was checked on 7 October 2026. Its stated product value must not be silently substituted for another brick, a local declaration or a whole-wall design value.