Psi-value and U-value Calculations

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Psi-value and U-value Calculations

In this lesson the calculations of Psi-values and U-values of some typical flixo applications are explained.

The goal of these examples is to illustrate the Psi-Value tool and the U-Value tool and to show typical cases where these  tools are used in a meaningful way.

A Psi-value is mainly a value of adjustment during the calculation of energy loss of building surfaces. It quantifies the additional energy loss per degree Kelvin and linear meters which wasn't taken into account with the simplified approach of the energy loss calculation using U-values and areas. The calculation of the Psi-value therefore depends strongly on the calculation method of the simplified approach. These are defined in international and national standards. Therefore the same construction can have different Psi-Values depending on the national standard for the calculation of transmission losses!

The calculation of Frame U-Values according to EN ISO 10077-2 is explained in detail in lesson 4.