01 02 03 04 05 06 07 08 09 10

Heat transfer coefficient (U value)

The heat transfer coefficient (unit = W/m²K) refers to a structure and indicates the heat flow through a standard cross-section over an area of 1 m² per unit of time.

U values for different insulation thicknesses (source: Dipl.-Kfm. Tobias Weißgerber, Marketing, ft Fenster & TürenForm GmbH, adapted)

This value is particularly important for comparing different structures. It is not a material-specific value, like the λ value, but is calculated from the thermal conductivity of the material (λ value) and the thickness of the insulation layer; so it always depends on the structure selected.

The smaller the U values (of building components), the lower the heating energy consumption (of the room enveloped by these building components).