Thermal conductivity, also referred to as the lambda value ‘λ-value’ or ‘K-value’, dictates the insulating ability of a material and is a key factor in designing insulation strategies that achieve stringent building fabric thermal performance.
The lambda value is the rate of transmission of energy through 1m2 of material, 1m thick with a 10oC temperature difference on both sides. It measures a product’s thermal conductivity in units of W/m·K.
The lower the lambda value of an insulation product, the better it performs.
The ‘K-value’ or ‘λ-value’ is used when calculating an R-value.