Thermal Conductivity (λ)
Thermal conductivity (lambda, λ) measures how readily a material conducts heat, in W/m·K. Lower λ means a better insulator. For insulation it rises with temperature, so the λ-curve at operating temperature — not a single value — determines real heat loss.
λ quantifies heat flow through a material for a given thickness and temperature difference. Insulation materials have low λ (good insulators), but λ increases with mean temperature, so honest heat-loss calculations use the λ-value at the actual service temperature. Standards such as BS EN ISO 13787 define how the declared λ-curve is determined.
Related terms
U-value (Thermal Transmittance) · Emissivity (ε) · Waste Heat Recovery
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