2017-05-10 / News

News from the Warm Edge Task Force

The data sheets with representative Psi values for windows and façades that are issued by the Federal Flat Glass Association (BF) are well-known far beyond Germany’s borders. They are popular because they provide a simplified means of proving the Uw-value of windows.

A new project from the BF Warm Edge* task force should now strengthen confidence in these data sheets and their acceptance even further.

The authoritative Psi values of the BF data sheets are calculated in accordance with ift guidelines WA-08 and WA-22. These calculations are based on what is called the equivalent thermal conduction capacity λeq,2B that is determined metrologically in accordance with ift guideline WA-17. This value plays an especially important role. When using the 2-box model for calculating Psi values, the equivalent thermal conduction capacity together with the height of the spacer (height of box 2) defines the respective spacer.

The members of the task force have now voluntarily committed themselves to having the information regarding thermal conduction capacity verified independently by ift Rosenheim every two years. This should ensure that any deviations from the original measurements are detected, or that the stated values are still correct even after several years. The costs for verifying the thermal conduction capacity will be covered by the manufacturers themselves. With the start of the first re-measurements in 2018, in future the BF data sheets will be valid for a period of two years.

* The 'Warm Edge' task force is a subcommittee of the technical committee for the Federal Flat Glass Association (BF). The task force is made up of members and supporting members of the BF. The task force is supported scientifically by Prof. Dr. Franz Feldmeier of the University of Applied Sciences in Rosenheim, and Dipl.-Phys. Norbert Sack from the ift Rosenheim [Rosenheim Window Institute].