The length-related heat transfer coefficient, called Ψ value, indicates the heat transfer through the edge seal for windows and is based on DIN EN ISO 10077-2.

The Ψ value is given in watts per meter and Kelvin. The Ψ value of a frame profile is automatically determined in WINISO^®. The glass structure is replaced by a calibration panel for the first calculation run. The original glass pane is restored for the second calculation run.