Determining thermal transmittance

Thermal transmittance (U-value) is a specific characteristic value for the heat transfer through a building component. The U-value indicates the amount of heat that passes through 1 m2 of a building component at a temperature difference of 1 K. It is essentially determined by the thermal conductivity and the heat transfer coefficient. It is essentially determined by the thermal conductivity and thickness of the materials used.

Test/ method

The U-value can be determined by the following methods:

Calculation, also with a computer calculation programme (DIN EN ISO 10077-2)

Reading from tables (DIN EN ISO 10077-1)

Building elements/ Relevant standards:

Windows, doors and facades, roller shutter boxes

DIN EN ISO 10077-1

Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 1: General

DIN EN ISO 10077-2

Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 1: Numerical method for frames

DIN EN ISO 12631

Thermal performance of curtain walling – Calculation of thermal transmittance

Closures (e.g. window shutters, roller shutter curtains)

DIN EN ISO 10077-1

Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 1: General

DIN EN ISO 10077-2

DIN EN ISO 10077-2

Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 1: Numerical method for frames

DIN EN 13125

Closures Additional thermal resistance

Doors

DIN EN 12428

Doors – Thermal transmittance Requirements for calculations

Minimum requirements in Germany according to GEG 2020: